Parasites of the African painted dog (Lycaon pictus) in
captive and wild populations: Implications for conservation
Amanda-Lee Ash
Bachelor of Animal and Veterinary Biosciences (Hons)
La Trobe University, Victoria
Faculty of Health Sciences
School of Veterinary and Biomedical Sciences
Murdoch University
Western Australia
This thesis is presented for the degree of Doctor of Philosophy of Murdoch University 2011
i I declare that this thesis is my own account of my research and contains as its main content work which has not previously been submitted for a degree at any other tertiary educational institution.
……………………………..
Amanda-Lee Ash
ii Abstract
The African painted dog (Lycaon pictus) is a highly endangered carnivore of sub-
Saharan Africa, which in the last century has suffered a population decline of almost
99%. With only 3,000-5,500 animals remaining in the wild it is imperative to understand all threatening processes to which these animals may be exposed. The impact that parasites and other infectious agents have on wildlife has been increasingly
recognized within conservation programs. Stressors such as human encroachment and
habitat destruction are altering the incidence and effect that these pathogens have on
wildlife populations, especially those endangered and under stress.
A parasitological study was conducted on captive and wild populations of the African
painted dog over a three year period. Collaborations with three captive animal facilities
and three in situ conservation groups within Africa allowed for a broad sample base
from which variation in parasite prevalence and diversity could be identified. A
combination of traditional microscopy techniques and molecular characterisation of
parasite species were employed to obtain comprehensive data on the prevalence and
diversity of gastrointestinal parasites observed in faecal samples collected from painted
dogs.
Parasite prevalence within wild populations was 99% with a similar parasite
community composition observed among all three wild populations. Five of the seven
parasite genera observed in this study have not been reported before in this host.
Additionally, molecular characterisations identified the potentially zoonotic species
Giardia duodenalis, Ancylostoma braziliense and an ambiguous species of taeniid, all
of which have also not been previously reported in this host.
iii The prevalence of parasites within captive populations was 15% with Giardia
duodenalis being the dominant of the only two parasite species observed. The overall
lack of prevalence and diversity of parasites observed in captive populations could be
of significance for facilities involved in reintroduction programs. Particularly as
immunologically naïve captive animals may be unable to cope with exposure to a
‘natural’ parasite load in the wild environment, leading to an ultimate decrease in
reintroduction success.
Gastrointestinal parasites detected in faecal samples from wild and captive populations
of the African painted dog during this study
Wild Captive Parasite Taxon Taeniid Giardia observed Ancylostoma Spirometra Spirometra Giardia Coccidia Sarcocystis Filaroides
This study has obtained detailed baseline data of parasitism within populations of the
African painted dog in captive and wild environments. The large proportion of new discoveries in this study demonstrates the paucity of information currently available on parasitism within this host species. It is hoped this information will assist in conservation efforts by a) recognising the challenges of parasite control in captive populations, particularly those involved in reintroduction and/or translocation programs, and b) being able to identify deviations from baseline parasite levels in wild populations which could be indications for emerging exotic and/or zoonotic disease.
iv Publications
Refereed journal articles:
Ash, A., Lymbery, A., Lemon, J., Vitali, S., Thompson, R.C.A. (2010). Molecular epidemiology of Giardia duodenalis in an endangered carnivore – the African painted dog. Veterinary Parasitology, 174, 206-212.
Conferences
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2010). Significance of parasitism
in an endangered carnivore - the African painted dog. Conference Proceedings: XX11
International Congress of Parasitology, Melbourne, Australia. (Abstract)
Ash, A., Lymbery, A., Lemon, J., Vitali, S., Thompson, R.C.A. (2009). Giardia
duodenalis isolates from captive and wild populations of the African painted dog
(Lycaon pictus). Conference Proceedings: ASP & ARC/NHMRC Research Network
for Parasitology Annual Conference. Sydney, Australia, pp 54. (Abstract)
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2009). Parasites of the African
Painted dog (Lycaon pictus) in wild and captive populations: potential conservation impacts. Conference Proceedings: 22nd Conference of the World Association for the
Advancement of Veterinary Parasitology (WAAVP), Calgary Canada, pp 86.
(Abstract)
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2008) Parasites of the African
painted dog (Lycaon pictus) in wild and captive populations: potential conservation
v impacts. Conference Proceedings: 21st Australasian Wildlife Management Society
Conference. Fremantle, Australia, pp 44. (Abstract)
Ash, A., Lymbery, A., Lemon, J., Thompson, R.C.A. (2007). Parasites of the African painted dog (Lycaon pictus) in wild and captive populations: potential conservation impacts. Conference Proceedings: ASP & ARC/NHMRC Research Network for
Parasitology Annual Conference. Canberra, Australia, pp 95. (Abstract)
vi Acknowledgements
I would firstly like to thank my three supervisors, Andy Thompson, Alan Lymbery and
John Lemon for their invaluable guidance throughout this project.
Secondly, the fabulous field assistance given by the staff of the Zambian Carnivore
Project (Matt Becker, Egil Droge and Claire Harrision) and the Wild Dog Project
(Robin Lines and Anna) for making my forays into deepest Africa a little less daunting.
I now have the ability to navigate rough muddy roads in various 4WD vehicles and deal
with angry elephants, hungry hyaena, thieving baboons and the ever present lion all in the quest for African painted dog poo. Additionally the staff at DeWildt wildlife trust
(Alan and Gabby) for assistance and protection in roaming occupied enclosures for
samples, whilst also chasing cheetah out of trees. And of course the keepers and vets at
Perth and Monarto zoo.
Thirdly, the assistance I was given in the lab was lifesaving. I was fortunate in having
access to expertise from various people including Cath Covacin, Aileen Elliot, Russ
Hobbs and Louise Pallant, all of which made my task that much easier. Additionally,
the post-grad office crowd were always available for a little light comic relief.
And finally, to all my family and friends who tried not to think I was completely mad
for taking on a doctorate and for R who was a calming influence during the rough and
rocky patches of field work, lab work and write up.
vii Table of Contents
Abstract ...... iii
Publications ...... v
Conferences ...... v
Acknowledgements ...... vii
Table of Contents ...... viii
List of Tables ...... xiv
List of Figures ...... xviii
Chapter 1 Introduction ...... 1
1.1 Parasites in wildlife ...... 2
1.2 Importance of parasites in conservation ...... 2
1.2.1 Direct impacts ...... 4
1.2.2 Indirect impacts ...... 8
1.2.3 Co-extinction events/biodiversity considerations ...... 11
1.2.4 Assessing effects of human influences ...... 12
1.3 The host, the African painted dog (Lycaon pictus)...... 14
1.3.1 Ecology of the African painted dog ...... 15
1.3.2 Conservation issues for the African painted dog ...... 16
1.4 Parasites and the African painted dog ...... 17
1.4.1 Host ecology and parasites ...... 17
1.4.2 Parasites recorded from the African painted dog ...... 18
1.4.3 Gaps in current knowledge of parasitism in the African painted dog ...... 20
1.5 Management of wild species ...... 21
viii 1.5.1 Captive environments ...... 21
1.5.2 Reintroduction programs ...... 23
1.5.3 Translocation programs ...... 23
1.6 Goals for this study ...... 24
Chapter 2 General materials and methods ...... 27
2.1. Study design ...... 28
2.2 Captive populations ...... 29
2.2.2 Perth Zoo ...... 29
2.2.3 Monarto Zoo ...... 31
2.2.3 DeWildt Wildlife Trust ...... 32
2.3 Wild populations ...... 33
2.3.1 South Luangwa National Park – Zambia ...... 33
2.3.2 Nyae Nyae Conservancy – Namibia ...... 35
2.3.3 Hwange National Park – Zimbabwe ...... 36
2.4 Sampling methodology ...... 37
2.4.1 Ethics and permits ...... 38
2.4.2 Locating packs ...... 39
2.4.3 Sample collection ...... 40
2.4.4 Sample movement ...... 41
2.5 Parasitological techniques ...... 42
2.5.1 Microscopy; qualitative analysis ...... 42
2.5.2 Microscopy; quantitative analysis ...... 44
2.5.3 Molecular characterisation ...... 45
ix Chapter 3 Diversity and prevalence of gastrointestinal parasite fauna within captive and wild populations of the African painted dog ...... 46
3.1 Introduction ...... 47
3.2 Materials and methods ...... 49
3.2.1 Sampling protocol ...... 49
3.2.2 Parasite identification and quantification ...... 51
3.2.3 Host and environmental variables ...... 52
3.2.4 Data analysis ...... 52
3.2.4.1 Descriptors used ...... 52
3.2.4.2 Levels of testing ...... 53
3.2.4.3 Statistical analysis ...... 55
3.3 Results ...... 56
3.3.1 Variation between captive and wild populations ...... 56
3.3.2 Variation between packs ...... 58
3.3.3 Variation among different geographic locations ...... 60
3.3.4 Variation between different seasons ...... 62
3.3.5 Variation between host age and sex ...... 64
3.3.6 Parasite aggregation within hosts ...... 64
3.4. Discussion...... 65
3.4.1 Parasite diversity ...... 65
3.4.2 Influence of geographic, seasonal and demographic factors ...... 68
3.4.3 Parasites of wild and captive populations ...... 70
3.4.4 Conclusions ...... 71
Chapter 4 Molecular epidemiology of Giardia duodenalis in an endangered carnivore – the African painted dog ...... 72
4.1 Introduction ...... 73
x 4.2 Materials and methods ...... 75
4.2.1 Sample collection ...... 75
4.2.2 Parasitological techniques ...... 75
4.2.3 DNA extraction ...... 76
4.2.4 Amplification of 18S rRNA locus ...... 76
4.2.5 Amplification of β-giardin locus ...... 77
4.2.6 Amplification of the glutamate dehydrogenase locus ...... 78
4.2.7 Data analysis ...... 79
4.3. Results ...... 80
4.3.1 Prevalence of infection ...... 80
4.3.2 Molecular characterization of Giardia duodenalis isolates ...... 81
4.4. Discussion...... 84
4.4.1 Conclusions ...... 89
Chapter 5 Hookworm species of the African painted dog and the significance of infection ...... 90
5.1 Introduction ...... 91
5.1.1 Hookworm in the canid host ...... 92
5.1.2 The zoonotic potential of canid hookworm species ...... 93
5.1.3 Hookworm in the African painted dog and other carnivores in Africa ...... 94
5.1.4 Diagnosing hookworm infections ...... 95
5.2 Materials and methods ...... 96
5.2.1 Sample collection ...... 96
5.2.2 Parasitological techniques ...... 96
5.2.3 DNA extraction ...... 97
5.2.4 Amplification of Ancylostoma spp. isolates at the ITS1 and ITS2 regions ...... 97
5.2.5 Data analysis ...... 98
xi 5.3 Results ...... 98
5.3.1 Prevalence of infection ...... 98
5.3.2 Molecular characterisation of Ancylostoma spp. isolates ...... 100
5.4 Discussion...... 101
5.4.1 Conclusions ...... 106
Chapter 6 Detecting Taenia species of the African painted dog ...... 108
6.1 Introduction ...... 109
6.2 Materials and methods ...... 114
6.2.1 Sample collection ...... 114
6.2.2 Parasitological techniques ...... 115
6.2.3 Identification of proglottids ...... 115
6.2.4 DNA extraction ...... 116
6.2.5 Amplification of Taeniid isolates at the 12S rRNA locus ...... 116
6.2.6 Data analysis ...... 117
6.3 Results ...... 118
6.3.1 Prevalence of Infection ...... 118
6.3.2 Identification of taeniid spp. proglottids ...... 120
6.3.3 Molecular characterisation of taeniid sp. isolates ...... 121
6.3.4 Phylogenetic analysis of Taenia spp. isolates ...... 124
6.4 Discussion...... 125
6.4.1 Conclusions ...... 129
Chapter 7 General discussion ...... 130
7.1 Conservation status of the African painted dog ...... 131
7.2 Increasing importance of studies of parasites ...... 131
xii 7.3 Parasitological techniques ...... 132
7.4 Implications for biodiversity conservation ...... 133
7.5 Parasitism in natural populations ...... 134
7.5.1 Baseline data ...... 134
7.5.2 Parasite threats to painted dogs ...... 135
7.5.3 Zoonoses/anthropozoonoses ...... 136
7.6 Parasitism in captive populations ...... 137
7.7 Project limitations and future research ...... 138
7.7.1 Sample collection and analysis ...... 138
7.7.2 Continued surveillance ...... 139
7.7.3 Threat of emerging disease ...... 140
7.7.4 Captive management ...... 140
Appendix 1. Taenia spp. proglottid key. From Verster (1969) ...... 142
References ...... 143
xiii List of Tables
Table 1.1 An overview of the major factors of the host/parasite relationship.
Positive effects are those that are assumed to be beneficial to an
individual or population of hosts; negative effects are assumed to be
harmful to an individual or population of
hosts………………………………………………………..……………4
Table 1.2 A brief natural history of parasites observed in the African painted dog…………………………………………………………………19-20
Table 3.1 Number of faecal samples obtained from all captive and wild
populations during the study period….……………………………….50
Table 3.2 A hierarchical list of comparisons made between host groups with
descriptions of the data used at each level……………………….….…54
Table 3.3 The prevalence (with 95% confidence intervals in parentheses) and
diversity of GI parasites detected in faecal samples from all captive and
wild populations of the African painted dog……………………..……57
Table 3.4 Prevalence (with 95% confidence intervals in parentheses) of GI
parasites detected in faecal samples from two packs within the Zambian
study population………………………………………………….…….58
Table 3.5 The overall prevalence (with 95% confidence intervals in parentheses)
and diversity of GI parasites detected in faecal samples from three wild
populations - Zambia, Zimbabwe and Namibia…………………..…...61
xiv Table 3.6 Prevalence of the main GI parasites (with 95% confidence intervals in
parentheses) detected in faecal samples from all wild populations in wet
and dry
seasons………………………………………………………………....62
Table 3.7 Aggregation of parasite species within host populations in Zambia,
Namibia and Zimbabwe using the Index of Discrepancy values (D).…65
Table 3.8 GI parasite genera observed in this study and in the published
literature………………………………………………………………..65
Table 4.1 Prevalence of Giardia duodenalis (with 95% confidence intervals in
parentheses) detected in faecal samples from captive and wild
populations of the African painted dog……………………..…………80
Table 4.2 Genotypic characterisation of Giardia duodenalis isolates from
individual African painted dogs at the18S rRNA, β -giardin and gdh
loci. * Wild animals over 2yrs of age were allocated as Adult……...…82
Table 4.3 Prevalence (with 95% confidence intervals in parentheses) and
genotypic characterisation of Giardia isolates obtained in a captive
population of African painted dogs over a three year period………….83
Table 4.4 Assemblages of Giardia duodenalis observed in both wild canids and
domestic dogs noted in the literature and this study. Number of times
reported in literature is presented as (r=)…………………………….86
Table 5.1 Prevalence of Ancylostoma spp. (with 95% confidence intervals in
parentheses) detected in faecal samples from captive and wild
populations of the African painted dog………………………………99
xv Table 5.2 Prevalence of Ancylostoma spp. observed in the Zambian and Namibian
populations of the African painted dog over a three year period. Sample
size (n) and 95% confidence intervals in parentheses……….…….....99
Table 5.3 Genotypic characterisation of Ancylostoma spp. isolates obtained from
wild populations of the African painted dog within Zambia and
Namibia. Percentages for matched identities with published sequences in
parentheses…………………………………………...……………….100
Table 5.4 Summary of the nucleotide variations detected between the painted dog
isolate from Zambia (Z-Ka01) and reference sequences for A. caninum
and A. duodenale. Alignment was conducted in Sequencher™ 4.8 and
dots indicate identity with the first sequence…………...…………….101
Table 6.1 Definitive and intermediate hosts of Taenia spp. infecting African
carnivores………………………………………………...…………...112
Table 6.2 Prevalence of taeniids (with 95% confidence intervals in parentheses)
detected in faecal samples from wild populations of the African painted
dog………………………………………………………..…………..119
Table 6.3 Prevalence of taeniids observed in the Zambian and Namibian
populations of the African painted dog over a three year period. Sample
size (n) and 95% confidence intervals in parentheses……..…………119
Table 6.4 Species identification of taeniid proglottids obtained from painted dog
populations……………………………………………...…………….120
Table 6.5 Genotypic characterisation of taeniid spp. species isolates obtained from
wild populations of the African painted dog within Zambia, Namibia
xvi and Zimbabwe. Percentages for matched identities with published
sequences on GenBank in parentheses……………………………….122
Table 6.6 Summary of the nucleotide variations detected between taeniid isolates
from Zambian and Namibian populations of the African painted dog and
reference sequences for T. multiceps and T. serialis (GenBank accession
numbers GQ228818, DQ408418 and EU219546, DQ104238).
Alignment was conducted in Sequencher™ 4.8 and dots indicate identity
with the first
sequence……………………………………..………………………..123
Table 6.7 Pairwise comparison of sequence variation (%) within the 12S rRNA
loci of T. multiceps and T. serialis reference sequences and taeniid
isolates obtained from Namibian and Zambian populations of the
African painted
dog…………………………………..………………………………..124
xvii List of Figures
Figure 2.1 Location of painted dog study sites within Australia………………....29
Figure 2.2 Painted dog exhibit at Perth Zoo showing the water feature and animals
resting in the shade……………………………………………………30
Figure 2.3 Painted dog exhibit at Monarto zoo showing the animals in the large
fenced
enclosure……………………………………………………………....31
Figure 2.4 Painted dog enclosure at DeWildt Wildlife Trust showing grassy and
shady environment……………………………………………………32
Figure 2.5 Locations of the painted dog study populations within Africa……….33
Figure 2.6 South Luangwa National Park, Zambia. Open grassland area with acacia
and mopane woodland in the background, which is typical of the habitat
frequented by painted dog populations……………………………….34
Figure 2.7 Nyae Nyae Conservancy, Namibia. One of the few sandy roads
available to use, surrounded by thick grass and acacia trees………….35
Figure 2.8 Game managed area of Hwange National Park, Zimbabwe. Open area
with miombo woodland and acacia in the background, typical for
painted dog
habitat………………………………………………………………...37
Figure 2.9 The left and right side views of an individual painted dog from the
Katete pack in Zambia. ID number P3 0308………………………….40
Figure 2.10 Parasite ova of taeniid spp. and Giardia spp. cysts observed during
microscopy analysis of painted dog faecal samples. Morphology and xviii size are substantially different between the two genera, allowing for
unambiguous identification……………………………………………43
Figure 3.1 Parasite load (N), species richness (S) and species evenness (H) in
captive and wild populations of the African painted dog……………..56
Figure 3.2 Parasite load (N), species richness (S) and species evenness (H) in two
packs within the Zambian study population…………………………..59
Figure 3.3 A multidimensional scaling plot of data from two African painted dog
packs within the Zambian population based on Bray-Curtis similarity
coefficients of parasite infracommunity composition…………………59
Figure 3.4 Parasite load (N), species richness (S) and species evenness (H) in three
wild populations of the African painted dog…………………………60
Figure 3.5 Parasite load (N), species richness (S) and species evenness (H) between
wet and dry seasons in all wild populations of the painted dog………63
Figure 3.6 A multidimensional scaling plot of data from wet and dry environments
of three wild populations based on Bray-Curtis similarity coefficients of
parasite infracommunity……………………………………………….63
Figure 5.1 Depiction of the lifecycle of Ancylostoma caninum in domestic dogs
adapted from www.Apaws.org...... 92
Figure 6.1. The lifecycle of a taeniid species depicting the transmission cycle
between predator (definitive host) and prey (intermediate host)……111
Figure 6.2 A depiction of the genital atrium of T. crocutae as an example of the
morphological features used in identification of proglottids. From
Verster (1969). Appendix 1 displays the proglottid key used for
identifying samples obtained in this study……………………………116
xix Figure 6.3 Multiplex PCR of taeniid isolates from wild painted dog populations at
the 12S rRNA locus. Lanes 2-11 are painted dog samples from Zambia
and Namibia. Lane 13 is the negative control; 14-16 are the positive
controls for Taenia sp, E. granulosis and E. multilocularis…………121
Figure 6.4 Phylogenetic relationships, inferred using the Neighbour-joining method
between taeniid isolates from African painted dogs and reference
isolates of T. multiceps and T. serialis based on sequence data of the 12S
rRNA locus. Representatives of Taenia sp. used for comparison are
labelled with accession numbers as published on GenBank, with E.
granulosus as the out-group. Numbers at nodes refer to bootstrap values
(1500 replicates) > 20%.
………………………………………………………………………125
xx Chapter 1 - Introduction
Chapter 1
Introduction
1 Chapter 1 - Introduction
1.1 Parasites in wildlife
Comprehensive research on parasitism within wildlife populations has, to date, been minimal (De Leo and Dobson, 2002; Altizer et al., 2003a; Morand et al., 2006). Of these studies most have been focused on the threat disease may pose to livestock or human populations, rather than gaining insight into the biodiversity and role these host/parasite interactions have within the ecosystem (Hudson et al., 2006; Thompson et al., 2010).
Parasitism is the commonest life style on earth (Poulin and Morand, 2000) and parasites are therefore a major component of ecosystems. An increasing number of studies are showing that parasites are important in maintaining ecosystem function through their effect on regulating host population sizes, mediating predatory and competitive interactions among free living organisms and acting as ecosystem engineers (Anderson, 1972; Temple,
1987; Jones et al., 1994; Hudson et al., 1998). Therefore, understanding parasitism within wild populations should be an integral part of any wildlife monitoring program and a key component of wildlife conservation efforts.
1.2 Importance of parasites in conservation
As wildlife populations continue to decline, the need for active conservation of many species becomes vital. For this to be successful it is essential that there is a thorough understanding of all threatening processes within the wild environment (Peterson, 1991).
Until recently, there has been a very one dimensional view of the role played by parasites in wildlife conservation programs. Parasite infection has usually been considered simply as another threatening process which may require intervention (Daszak et al., 2000; Applebee et al., 2005; Deredec and Courchamp, 2006; Penzhorn, 2006; Thompson et al., 2010). The
2 Chapter 1 - Introduction reality however, is much more complex. An early study by Sachs and Sachs (1968), for example, noted that wild animals were often heavily parasitised, when compared with domestic animals, but showed apparent health. This display of health may be the result of acquired immunity by the host or, as has been previously noted, wild animals tend to manifest few recognizable signs of disease (Sachs and Sachs, 1968; Young, 1969). For example, wild populations of zebra are known to harbour a variety of Cyathostomum spp., of which several species are pathogenic to domestic equines, but the zebra host appears to display no clinical effects (Roberts et al., 2002). Sachs and Sachs (1968) qualified that this display of health should not be confused with non-pathogenicity of parasites in wild animals but rather a favourable balance between the host and its parasite community established through a long evolutionary process. This evolutionary process has often been referred to as an ‘arms race’ in reference to the constant battle between host and parasite to gain the upper hand (Dawkins and Krebs, 1979). The outcomes of this are complex host/parasite relationships which can be stable, cyclical or chaotic with equally complex effects (May and Anderson, 1983). The complexity of the co-evolutionary relationship between host and parasites means that parasitism can have both positive and negative effects for individual hosts, for host populations and for communities of free living organisms (Table 1.1). These effects arise because of both the direct impact of parasites in causing disease and indirect impacts of parasites in mediating competitive and predatory interactions among free-living organisms.
3 Chapter 1 - Introduction
Table 1.1 An overview of the major factors of the host/parasite relationship. Positive effects are those that are assumed to be beneficial to an individual or population of hosts; negative effects are assumed to be harmful to an individual or population of hosts.
Factor Effects at individual level Effects at population/community level
Positive Negative Positive Negative
Direct impacts of parasitism
Clinical & Development of Morbidity and Avoiding Local extinction host immune death of susceptible overpopulation Sub-clinical system individuals disease Maintenance of genetic diversity
Regulating host Development of Reduced fecundity Increased host Decreased host population size host immune and survival of host population size population size system
Indirect impacts of parasitism
Interspecific Increased Decreased Increased resources Local extinction of competition competitive success competitive success for successful unsuccessful competitor species competitor species
Manipulation of Increased prey Increased predation Increased Reduced population prey behaviour capture rate population size of size of prey species predator species
1.2.1 Direct impacts
The direct impacts of clinical disease from parasitism on the host are largely negative at both the individual and population level as a significant parasite burden can lead to severe morbidity or death. For example, at the individual level a heavy infection of hookworm in young or immunocompromised animals can lead to severe anaemia and death of those individuals (Bowman et al., 2003). At the population level gastro intestinal (GI) parasites
4 Chapter 1 - Introduction such as Trichostrongylus sp. are capable of inducing large population crashes in wild and domestic species. Hudson et al. (1992) observed this in wild populations of red grouse, whilst livestock farmers have had long standing battles to reduce heavy stock losses due to strongyle infections (Herlich, 1978; Fabiyi, 1987). Less obvious are the effects of subclinical disease on the host however, there is growing evidence to suggest the effects can be severe. One example is the protozoan parasite Giardia spp. Infection with this parasite is often asymptomatic but studies have shown that long term infections can lead to growth retardation in the host, particularly when suffering from poor nutrition (Astiazaran-
Garcia et al., 2000; Berkman et al., 2002). Whilst studies on Giardia spp. have been focused on human infections this parasite is becoming increasingly recognised in wildlife populations and therefore may be of similar significance, especially to endangered populations with declining food resources. Evidence for this has been seen in a study on red colobus monkey (Piliocolobus tephrosceles) populations living in fragmented forests of Uganda (Chapman et al., 2006). This study found that populations of red colobus monkeys, which were experiencing a decline in food availability, were at greater risk of the detrimental effects of gastrointestinal parasites.
To further complicate matters, wild hosts are often infected with more than one parasite
(polyparasitism) which can sometimes alter or amplify the effects of any subclinical disease. A recent example of this was illustrated in a study by Munson et al. (2008) who conducted an analysis of historical data of canine distemper virus (CDV) epidemics within populations of the African lion. They discovered that these epidemics coincided with unusually high levels of the blood parasite Babesia, which were in turn the result of high exposure to the tick vector after periods of drought. Babesia infections in wild hosts are
5 Chapter 1 - Introduction often stable but this study suggests that the subclinical effects of this parasitic infection can leave the host susceptible to other pathogens (Penzhorn, 2006; Munson et al., 2008). These complex interactions make the ability to detect the causative agent of disease within hosts harbouring multiple parasites extremely difficult. Compiling comprehensive baseline data and conducting continual surveillance on the parasite fauna within different wild host populations may increase the chances of detecting and predicting these pathogenic outbreaks.
Consequences of clinical and subclinical disease may include the regulation of host populations. Mathematical modelling has shown that parasites can provide density dependent regulation of their host populations through effects on both host mortality rates and host fecundity rates (May and Anderson, 1978; McCallum and Dobson, 1995). This has been successfully demonstrated in laboratory studies of helminth infections in snails, fish and mice (Scott and Anderson, 1984; Anderson and Crombie, 1985; Scott, 1988). For example, the nematode Heligomosomiides polygyrus introduced into mice populations resulted in dramatically reduced host densities, which subsequently increased on removal of the nematode (Scott, 1987). This has also been demonstrated in a wild population of red grouse (Lagopus lagopus scotius) and the nematode Trichostrongylus tenuis (Hudson et al., 1992; 1998). Experimental removal of this parasite from populations of red grouse led to greater clutches, higher hatching success and chick survival, however the control population continued to display reduced fecundity and cyclical population crashes.
A lesser known aspect of parasitism is the beneficial effects which may be gained by the host. As a result of the evolutionary arms race between host and parasite it has been
6 Chapter 1 - Introduction proposed that parasites actively promote host immune systems and drive genetic diversity, and consequently act as a buffer against disease (Windsor, 1998; Altizer et al., 2003a;
2003b; Lindstrom et al., 2004; Maillard and Gonzalez, 2006). Early exposure to parasites can allow the host to build up effective immunity to withstand later heavy challenges. For example, Carroll and Grove (1985) demonstrated that dogs currently infected with small numbers of hookworms developed a functional protective immunity when challenged with a large inoculum of infective hookworm larvae, whereas dogs previously uninfected with hookworm developed marked anaemia when challenged with the same large inoculum. A similar benefit observed is con-concomitant immunity which is the ability of the host to mount an effective defence against parasite larval stages whilst being unable to clear a burden of adult worms (Smithers and Terry, 1969). This can create an immunological barrier against continual infection and restrict burden size within the host. The most common examples of this are the schistosomes whereby immunologically invisible adult worms established within the host are responsible for generating an anti larval immune response which prevents any subsequent infection (Smithers and Terry, 1969).
Another perspective is the well documented theory of the ‘hygiene hypotheses’ (Cookson and Moffatt, 1997; Yazdanbakhsh et al., 2002; Cooke et al., 2004). This has been referred to principally within human hosts and proposes that completely eradicating and/or limiting exposure of parasites from the host in a short evolutionary time span can lead to a disruption in the host immune system resulting in autoimmune diseases such as ulcerative colitis, asthma and other allergies (Yazdanbakhsh et al., 2001; Lakatos et al., 2004; Whary and Fox, 2004). Evidence for this was documented in a human trial with long-term
Crohn’s disease patients who were seen to have a marked decrease in symptoms when
7 Chapter 1 - Introduction infected with a nematode known to be non-pathogenic to humans Trichuris suis (Summers et al., 2005). This study proposed that the introduction of a parasite into the host reinstated normal functionality of the immune system.
Host genetic diversity is known to play an important role in enabling natural populations to withstand widespread epidemics and is especially important in declining populations
(Frankham, 2005). Parasites represent powerful selective agents in natural populations and are consequently a driving force behind species and genetic diversity (Altizer et al.,
2003b). This was demonstrated in a study of wild populations of Soay sheep (Ovis aries) infected with intestinal nematodes (Paterson et al., 1998). Allelic variation within the major histocompatibility complex (MHC) of Soay sheep was significantly associated with juvenile survival and parasite resistance and it was concluded that parasites played a large role in maintaining genetic diversity within this host population.
1.2.2 Indirect impacts
The indirect impacts of parasitism are comparatively less well understood than are the direct effects, but studies are demonstrating the significance these interactions have within ecosystems (Loreau et al., 2005). Parasites have been observed to be capable of mediating interspecific competition between host populations and manipulating predator/prey dynamics (Anderson, 1972; May and Anderson, 1978; Hudson et al., 1992; McCallum and
Dobson, 1995; Hudson et al., 1998; Jog et al., 2005; Barnes et al., 2007).
8 Chapter 1 - Introduction
Interspecific competition mediated by parasites has the potential to influence the structure of ecological communities, the viability of each species within a community and the potential for new species to invade a community (Thomas et al., 2005). An example of parasite mediated competition has been observed in populations of white tailed deer
(Odacoileus virginiatus) infected with the parasite Parelaphostrongylus tenuis. White tailed deer show minimal effects to an infection with this parasite but other cervids suffer severe neurological effects and death (Anderson, 1972). This prevents invasion by exotic cervids, leaving the white tailed deer with substantially less competition for food resources in the area (Anderson, 1972). The inability to introduce domestic cattle into tsetse fly zones of Africa is another example of parasite mediated competition. Tsetse flies are the vector for Trypanosoma brucei and T. congolense which cause fatal nagana disease in domestic ruminants, but are relatively non-pathogenic to the native wild ruminant population, thus hindering the introduction of exotic species to this habitat (Bowman et al.,
2003).
Another parasite mediated effect within ecosystems is that of manipulation of prey species.
It is perhaps well recognised that predators regulate prey population size but what is not acknowledged is the role parasites potentially play in this interaction. Parasites with complex indirect life cycles often rely on their intermediate host being consumed by a predator in order to complete their life cycle (Choisy et al., 2003; Poulin, 2007). As a means to increase the chances of reproduction some parasites appear to have adopted methods of manipulating the behaviour of the intermediate host enabling easier capture by predators. Temple (1987) conducted a study comparing levels of parasitism in prey items caught by a tame hawk and those he shot with a gun. He found that prey captured by the
9 Chapter 1 - Introduction hawk had higher intensity and prevalence of trematodes, nematodes and ectoparasites, than those shot and suggested parasitism was involved in mediating easier capture by the hawk.
Several studies have since attempted to identify the mechanisms by which parasites are able to achieve this. One example of this involves the cestode, Echinococcus. The metacestodes of Echinococcus spp. cause hydatid disease in the intermediate host, usually a herbivore, through the formation of cysts in the hosts organs (Thompson and Lymbery,
1988). These cysts can often form in the lungs, greatly reducing the animals’ ability to evade capture by a predator which is the definitive host for this parasite (Fenstermacher,
1937; Cowman, 1947; Joly and Messier, 2004; Barnes et al., 2007). Similar observations have been made with the coccidian Sarcocystis spp. (Jog et al., 2005; Jog and Watve,
2005). These studies observed that sarcocyst-infected prey (chital deer, Axis axis) were preferentially taken by the predator (dhole, Cuon alpinus) and although there was no evidence of clinical signs in the infected prey it was suggested that the large number of cysts in the heart would compete for oxygen and reduce the ability to evade capture.
Although these examples of parasite mediated increases in predation are often assumed to be adaptations by the parasite to manipulate prey behaviour, they may simply be by- products of parasitism. In some cases, however, the adaptive nature of parasite manipulations has been confirmed. For instance, studies have shown that rats infected with the protozoan Toxoplasma gondii, display specific behavioural changes that increase the parasites chances of transmission (Berdoy et al., 2000). Infected rats were found to display a preference for areas frequented by cats and were therefore vulnerable for predation. The cat is the definitive host for T. gondii and hence transmission for this parasite was increased.
10 Chapter 1 - Introduction
1.2.3 Co-extinction events/biodiversity considerations
In addition to the positive and negative effects of parasites on individual hosts and host populations, there is increasing recognition that parasites are important components of biodiversity in their own right. Parasites are the single largest component of biodiversity yet are often ignored by conservation biologists (Windsor, 1998; Poulin and Morand,
2000). Eradication and co-extinction events are severely affecting this biodiversity leading to possible adverse flow on effects (Koh et al., 2004; Dobson et al., 2008; Colwell et al.,
2009; Dunn et al., 2009). Parasites that are host specific run the same risk of extinction as their host and this is gaining recognition with studies advocating the need for the conservation of parasites along with their hosts (Dobson, 1995; Gompper and Williams,
1998; Daszak et al., 2000; Altizer et al., 2003a; Colwell et al., 2009). Dobson et al. (2008) estimated that the extinction of all species currently listed as threatened by the IUCN Red
List (IUCN, 2010) would lead to the co-extinction of c. 2000 species of helminth parasites.
Given the complexities of host/parasite interactions the loss of any parasite species may well result in detrimental effects to the host and the ecosystem (Gompper and Williams,
1998).
Besides co-extinction events another risk to host specific-parasites is their eradication in captive populations. Management of captive animals has a heavy focus on de-worming programs to ensure maximum health but has the adverse effect of causing possible extinction of host specific parasites. An example of this is the recovery program for the black footed ferret (Mustela nigripes). To prevent total extinction of the remaining wild population, all animals were captured and placed into captivity for later release. During this time efforts to minimize the threat of disease included the eradication of ectoparasites
11 Chapter 1 - Introduction within the population. It has since been proposed that a possible species of Neotrichodectes louse, which was unique to the black footed ferret may now be extinct (Gompper and
Williams, 1998). However, as there was limited baseline information on the parasite fauna of this host in the wild, positive confirmation of extinction was not possible. This provides another example highlighting the need for comprehensive data on the parasite fauna of wildlife hosts, particularly those endangered and being managed through conservation programs. Criteria for conserving these host-specific parasites may need to be incorporated into captive breeding programs to maintain the host parasite fauna and levels of immunity which are present in natural populations (Daszak et al., 2000; Gompper et al., 2003;
Penzhorn, 2006).
1.2.4 Assessing effects of human influences
All of these host/parasite interactions may be further complicated by the effects of habitat destruction/fragmentation and human encroachment (McCallum and Dobson, 1995; 2002;
Smith et al., 2009a; 2009b). These factors can lead to a disruption of the ‘normal’ host/parasite interactions, with possible detrimental effects to the host (May and Anderson,
1978).
Habitat destruction results in reduced species ranges and increased interactions between populations, which in turn raises the risk of disease transmission between these populations
(Scott, 1988; Lyles and Dobson, 1993). It can also result in limited resources for viable populations. The poor planes of nutrition and stress placed on these declining populations may then result in a rise in parasitic disease. For example, Penzhorn (2006) identified an
12 Chapter 1 - Introduction endemic stability of the haemoparasite, Babesia spp. in wild populations of lion and rhinoceros but when individuals of this species were placed under stress, clinical babesiosis was observed resulting in death of the host.
Perhaps of greater significance is human encroachment and the resultant increased interaction of humans and their domestic animals with co-habiting wildlife. Approximately
80% of domestic animal pathogens can infect wildlife so the risk of disease spillover into wild populations is potentially great (Kat et al., 1995; Cleaveland et al., 2001; Applebee et al., 2005). Examples of this have been documented in populations of the African painted dog and African lion which have suffered huge population declines due to spillover of rabies and canine distemper virus (CDV) from domestic dog populations (Kat et al., 1995;
Roelke-Parker et al., 1996). In these cases immunity had not been developed in the wild population, leaving them open to clinical disease. Another example highlighted by
Gillespie et al. (2005) illustrated the effects of human encroachment in a study on several primate species living in logged forests compared with those living in unlogged forest.
They identified higher parasite prevalence and richness in populations of the red-tailed guenon (Cercopithecus ascanius) living in logged forests compared to populations in unlogged forests. Along with a higher prevalence of parasites species including Trichuris,
Strongyloides and Entamoeba, three additional species were observed in the logged forest population which were Giardia sp., a liver fluke and Chilomastix mesnili. This study suggested that the human activity of logging had induced a change in the red-tailed guenon’s foraging behaviour which in turn increased their exposure to parasites.
13 Chapter 1 - Introduction
In summary, it would appear that parasites play a major role in the natural environment and are an essential component of any healthy ecosystem (Hudson et al., 2006). Additionally, these examples provide evidence of the need to increase surveillance of wildlife and build an extensive database of natural parasitism within wild populations from which a baseline can be formed. This will assist in the ability to identify potential emerging disease processes which may pose a threat to wildlife and should become an essential component in any wildlife management program.
1.3 The host, the African painted dog (Lycaon pictus)
Understanding the ecology of the host is important when attempting to understand parasitism within that host. Factors such as diet, behaviour and habitat provide insight into the spectrum of parasite fauna likely to exist within these populations.
The African painted dog (Lycaon pictus), also known as the African wild dog and painted hunting dog, is an endangered carnivore of sub-Saharan Africa which represents a unique genus of the canid family, having diverged from the rest of the dog family 3 million years ago (Girman et al., 1993; IUCN, 2010). Lycaon pictus translates to ‘painted wolf’ in reference to the mosaic of colours and patterns of the animals’ coat which are unique to each dog. The last century has seen the population decline by almost 99% from approximately 300,000 individuals to 3,000-5,500 with viable populations existing in only a few countries (Fanshawe et al., 1991; Woodroffe et al., 1997; IUCN, 2010). The cause of their decline has been a combination of human persecution, habitat loss, interspecific
14 Chapter 1 - Introduction competition and disease (Fanshawe et al., 1991; Woodroffe et al., 1997; Creel and Creel,
1998; Sillero-Zubiri et al., 2004).
1.3.1 Ecology of the African painted dog
African painted dogs are intensely social pack animals spending much of their time in close association with each other (Woodroffe et al., 1997). They are co-operative breeders and hunters which make them almost obligate pack animals in that survival outside the pack is minimal (Jennions and Macdonald, 1994; Creel and Creel, 1995). Painted dogs are extremely successful hunters and cooperative hunting allows them to bring down large prey, usually averaging 50 kg but sometimes as large as 200 kg (Malcolm and van Lawick,
1975; Creel and Creel, 1995). Their diet consists mainly of antelope such as impala, kudu and gazelle but may also include buffalo, hares and lizards (Creel and Creel, 2002; Pole et al., 2004; Hayward et al., 2006). Packs are based on a matriarchal society, with the alpha female governing pack movements. The alpha female and her chosen alpha male are usually the only pair to breed, whilst the rest of the pack assist in rearing the pups through hunting and pup-guarding (Malcolm and Marten, 1982; Creel and Creel, 1995). Studies suggest that in order to breed successfully packs need to consist of a minimum of five animals which allows for both hunting and pup-guarding to take place (Courchamp et al.,
2002; Sillero-Zubiri et al., 2004). This requirement indicates that maintaining pack numbers, rather than individuals, is vital to ensure continuation of the species (Creel and
Creel, 1995).
15 Chapter 1 - Introduction
The African painted dog is a nomadic species with home ranges greater than 2,000 km2.
The only time packs are stationary is during the denning season which is usually for three months or until the pups are old enough to follow the pack. During the denning season the pack, hunting diurnally, will return each time to the den to feed the pups by way of regurgitation of meat that they have consumed.
1.3.2 Conservation issues for the African painted dog
The predominant threat to the African painted dog is conflict with expanding human populations, specifically through habitat loss, human persecution and introduced disease
(Creel and Creel, 2002; Sillero-Zubiri et al., 2004). The lack of large protected areas
(greater than 10,000 km2) results in packs roaming outside national parks and into conflict with humans. Subsequently the risk of death and injury is markedly increased due to roads, where they are commonly killed, being caught in snare lines, which are set by poachers for bushmeat, and being shot or poisoned by livestock farmers (Fanshawe et al., 1991; van
Heerden et al., 1995; Creel and Creel, 1998; Rasmussen, 1999). Another human/wildlife conflict issue is that of domestic dogs. Painted dogs are vulnerable to diseases of domestic dogs such as rabies and canine distemper virus (CDV). Several painted dog populations have been adversely affected by epidemic outbreaks of these diseases with a possible extirpation occurring in the Serengeti ecosystem of Tanzania due to the rabies virus
(Alexander and Appel, 1994; Kat et al., 1996; Woodroffe, 1999). As these animals naturally live at low population densities catastrophic events such as these pose real threats to their continued conservation (Creel and Creel, 2002).
16 Chapter 1 - Introduction
Measures taken to counteract the dramatic decline in species numbers have included reintroduction and relocation programs. Currently there are approximately 400 animals in captivity according to the International Species Information System (ISIS). Many of these animals have had success in breeding, allowing for possible reintroductions. Few reintroduction programs, however, have taken place and most have had limited success
(Scheepers and Venzke, 1995; Woodroffe et al., 1997). Some wild populations in South
Africa are being actively managed as metapopulations, which involves translocation of animals between fenced wild populations to mimic natural immigration and emigration
(Davies-Mosert et al., 2009). Translocation programs are also used to move animals away from livestock farms, where conflict with farmers is occurring, and back into the relative safety of national parks.
1.4 Parasites and the African painted dog
As with most wildlife species, there has been only limited research on the parasites of the
African painted dog. In order to obtain a better understanding of the host/parasite relationship it is beneficial to understand the ecology of the host, obtain data on similar species and most importantly conduct longitudinal studies over several populations.
1.4.1 Host ecology and parasites
Parasitism is often heavily influenced by the ecology of the host, as the parasite will have adapted its life cycle according to host diet, behaviour and habitat. The African painted dog is a carnivore and therefore exposure to parasites will often be through ingested prey
17 Chapter 1 - Introduction species. These can act as intermediate hosts for parasites such as members of the cestode family Taeniidae, and the protozoans Toxoplasma gondii and Sarcocystis spp. Hunting in packs will see all individuals exposed to the same infected prey species. Additionally, as they are extremely social animals, other parasites requiring direct transmission between hosts such as Ancylostoma spp., Giardia spp. and ectoparasites will be easily transmitted between pack members (Altizer et al., 2003a). This would be especially important during the denning period when environmental contamination with parasite stages increase and subsequently transmission rates of these parasites between individuals would also increase
(Altizer et al., 2003b). Evidence for this has been seen with rabies virus epidemics which have wiped out entire packs (Kat et al., 1996). Finally, as these animals have large home ranges, packs will often move outside the park borders and through human communities, thereby raising the risk of them contracting exotic pathogens from domestic dogs (Creel and Creel, 2002).
1.4.2 Parasites recorded from the African painted dog
The dramatic decline of the African painted dog has lead researchers to focus on ecological factors such as pack dynamics, the effects of human/wildlife conflict and habitat fragmentation. The majority of information regarding the parasite fauna of the African painted dog comes from one study conducted in the early 90’s (van Heerden et al., 1994; van Heerden et al., 1995). This involved the sampling of 46 animals in Kruger National
Park over three one-week periods and information recorded on the presence of parasites from blood and faecal samples. The GI parasites that were reported consisted of Taenia sp,
Ancylostoma caninum and an unknown ascarid species. Toxascaris canis was also reported
18 Chapter 1 - Introduction but this species name is incorrect and was most likely Toxocara canis or Toxascaris leonina. The haemoparasites reported included Dipetalonema reconditum (microfilariae),
Hepatozoon sp. and Babesia sp. Apart from these studies, there have been incidental reports resulting from necropsy or parasite specific studies. Young (1975) observed E. granulosus from one dog in Kruger National Park, Bwangamoi et al. (1993) found
Sarcocystis-like organisms in three animals which had died from rabies. Colly and Nesbit
(1992) reported the death of a painted dog pup due to acute babesiosis. Babesia sp. and
Hepatazoon sp. were also reported by Nietz (1965), Peirce et al. (1995) and more recently
Matjilla et al. (2008). The natural history and importance of these parasites is described in more detail in Table 1.2.
Table 1.2 A brief natural history of parasites observed in the African painted dog.
Parasite species Transmission Description/lifecycle Importance
Ancylostoma sp. Direct ingestion or Small nematode in the small Severe anaemia may result skin penetration of intestine of the host, which in death of host. Possible infective larvae hooks onto the host and sucks zoonosis blood
Taenia sp. Indirect. Large tapeworms in the gut of Possible intestinal Intermediate host, the definitive host. Gravid obstruction of definitive usually a herbivore proglottids expelled onto host. Intermediate host may pasture and ingested by the be compromised due to intermediate host cysts forming in organs. Possible zoonoses
Echinococcus sp. Indirect. Small tapeworms in the gut of Non pathogenic to the Intermediate host, the definitive host. Gravid definitive host. Causes usually a herbivore proglottids expelled onto hydatid disease in the pasture and ingested by the intermediate host. Zoonosis intermediate host
Toxocara sp. Direct. Ingestion of Large roundworms in the Larval migrans may cause infective stage intestine of the host liver and lung damage. Possible zoonoses
Babesia sp. Indirect. Protozoan found in blood cells Anaemia and/or Transfer from tick of the host neurological disease species during a causing death bloodmeal
19 Chapter 1 - Introduction
Hepatozoan sp. Indirect. Protozoan in various tissues and May cause sub-clinical Transfer through white blood cells of the host disease in the host ingestion of infected tick
Sarcocystis sp. Indirect. A protozoan in the gut of the Non-pathogenic to the Intermediate host, definitive host definitive host. May cause usually a herbivore disease in the intermediate host
Dipetalonema Indirect. A small nematode in the Non-pathogenic to the reconditum Transfer from flea connective tissue of the host. definitive host or louse Also microfilariae in the blood stream which are taken up by vector during a blood meal
1.4.3 Gaps in current knowledge of parasitism in the African painted dog
The studies referred to above, whilst beneficial, only provide a ‘snap shot’ of parasitism within this endangered carnivore. Perhaps the most significant gap in knowledge is that of comprehensive baseline data which document the prevalence and intensity over time of parasitism within wild populations (Bjork et al., 2000; Mathews et al., 2006; Smith et al.,
2009a). The single random sampling studies commonly undertaken are not able to identify temporal or spatial variation of parasitic infection within the natural environment (Bjork et al., 2000). Longitudinal studies are required to obtain this information, which would then help to determine which potentially pathogenic agents to monitor within natural populations (Mathews et al., 2006; Smith et al., 2009b). Increasingly, there is recognition of the need for good surveillance of native fauna, which draws upon data from related species and uses longitudinal monitoring to identify and predict the parasites and pathogens of most importance (De Leo and Dobson, 2002; Smith et al., 2009b). Few studies have achieved this and to date none have been conducted on the African painted dog.
20 Chapter 1 - Introduction
1.5 Management of wild species
Human involvement has become pervasive in the management of nearly all wild species.
Most common is the management of wild animals in captive environments where the focus is on maintaining breeding populations and genetic diversity with the view to eventually reintroducing these animals to the wild. Management of wild populations has also increased as suitable habitat continues to decline and the use of translocation programs is required to move animals away from human conflict areas. Within both these management environments detailed knowledge of the ‘natural’ parasite fauna of a particular host may assist conservation efforts by monitoring for disease outbreaks, identifying exotic pathogens and perhaps allowing for natural immunity against some parasites (Phillips and
Scheck, 1991; Gompper and Williams, 1998; De Leo and Dobson, 2002).
1.5.1 Captive environments
In wildlife facilities with good veterinary practices, animals are more likely to be exposed to fewer parasites than their wild relatives. However, relatively low levels of parasitism may still result in clinical disease, as captivity places stress on wild species, which may affect the functioning of immune systems. Contrary to this, whilst complete eradication of parasites in captive populations is beneficial to the animal in the short term, this may later lead to under developed immune systems and a subsequent greater risk of clinical disease when exposed to pathogens (Windsor, 1997; Gompper and Williams, 1998; Penzhorn,
2006). Additionally, intensive housing, modern, grassy enclosures and mixed species enclosures may increase the opportunity for parasite transmission between species. On occasion, the parasites causing clinical disease are not a natural parasite of the species but
21 Chapter 1 - Introduction result from co-habiting with other species, cross-contamination from other enclosures, and modified behaviours commonly displayed in captive animals. For example, the tree browsing giraffe (Giraffa camelopardalis) when kept in modern, grassy enclosures will sit down and graze (Boomker et al., 1986; Garijo et al., 2004); this modified behaviour exposes them to parasites from the pasture that they would not normally encounter.
Fukumoto et al. (2004) reported the death of a giraffe due to a heavy infection of the nematode Camelostrongylus mentulatus, which is only obtained during grazing. This was compounded by the fact that the giraffe were housed together with camel and antelope, the natural hosts for this parasite.
Reports such as these, investigating unexpected deaths, are generally how parasitism is identified in captive environments. There are very few studies directly comparing parasitism among captive and wild populations. Muller-Graf et al. (1999) conducted a study on wild populations of lions and then made comparisons with retrospective reports of parasites in captive populations. Mas Bakal et al.(1980) investigating Toxoplasma gondii, made direct comparisons between captive and wild animals in Kenya, and Phillips and
Scheck (2001) compared captive and wild populations of red wolves during a reintroduction program. Whilst it is intuitive that there will be differences between the two environments, studies documenting specific differences in parasite prevalence and diversity remain elusive. Data such as these may greatly benefit facilities which use captive breeding and reintroduction programs as a conservation tool.
22 Chapter 1 - Introduction
1.5.2 Reintroduction programs
If when reintroducing captive bred animals into their wild environment, the type of parasite pressure to which the host is likely to be exposed is known, then measures can be undertaken to reduce this impact. A simple example of this was documented in a study on reintroducing captive bred red wolves (Canis rufus). Phillips and Scheck (1991) noted that it was beneficial to conduct reintroduction programs during winter when the tick burden was not as high, as in summer animals appeared to suffer from high infestations and this apparently reduced the success of the program. Pre-exposure to parasites or maintaining low levels of ‘natural’ parasite fauna within captive animals may limit the effect of the substantial parasite challenge they will face in wild environments (Viggers et al., 1993).
For example, when the last remaining population of black footed ferrets (Mustela nigripes) were taken into captivity, infections with the protozoan parasite Eimeria sp. were allowed to persist in order for the host population to maintain immunity for eventual release into the wild (Williams et al., 1992). Additionally, there is a risk of introducing exotic parasites, which animals have acquired from their captive facilities, into naïve wild populations
(Viggers et al., 1993; Cunningham, 1996). However, without detailed knowledge of what parasites are naturally found in the wild environment this would be difficult to predict and prevent.
1.5.3 Translocation programs
As with reintroduction programs the translocation of wild animals from one area to another may pose the risk of introducing exotic disease to either the existing population or the translocated animals (Davidson et al., 1992; Cunningham, 1996; Wyatt et al., 2008).
23 Chapter 1 - Introduction
Translocation is quite often a necessary tool for moving animals away from high human/wildlife conflict areas, stocking depleted populations or in the management of metapopulations (Davidson et al., 1992; Davies-Mosert et al., 2009). Again, having extensive baseline data on the parasite fauna of hosts in their natural environment in different geographic regions will help identify any risk of introducing possible pathogens to either population during these events (Cunningham, 1996). Cases of introducing exotic disease from translocation have often had devastating effects. Examples include the co- introduction of rinderpest with domestic cattle into East Africa which devastated the native ungulate population, and the protozoan (Myxobolus cerebralis) which causes whirling disease in trout and is believed to have been introduced from stocked European trout into native North American rainbow trout (Oncorhynchus mykissi) (Dobson, 1995; Bergersen and Anderson, 1997).
These examples provide evidence for the need to increase surveillance of wildlife and to build an extensive database on natural parasitism within wild populations from which a baseline can be formed. This will assist in the ability to identify potential emerging disease processes which may pose a threat to wildlife.
1.6 Goals for this study
Using the African painted dog as a model, this study aims to highlight the importance of obtaining comprehensive data on parasite biodiversity within an endangered species.
Longitudinal data obtained from several wild populations will provide a baseline on which further studies can build. Individual animal data such as sex, age and social status, when
24 Chapter 1 - Introduction available, is used to identify susceptibility to parasitism at the individual and population level. Additionally, environmental factors such as season or geography are incorporated into the analysis to determine if these are influential in the overall dynamics of parasitism within the natural environment.
To complement these data, the use of molecular tools will enable species identification, which has not been possible with traditional microscopy techniques. In many cases, molecular characterisation of parasites from faecal samples can eliminate the need for species identification from adult worms, which are usually only obtained during necropsy of animals. As the host involved in this study is endangered and obtaining animals for necropsy is almost impossible, these non-invasive methods provide the only way to gain further insight into the parasite fauna they harbour. Identification of parasite species will help to ascertain which are host specific, pathogenic, zoonotic or exotic to this species.
It is hoped that this information will assist in the conservation of the African painted dog in several ways:
providing a comprehensive database on the natural parasitism of Lycaon pictus
which will help identify exotic, zoonotic and emerging diseases within wild
populations.
recognising challenges of parasite control and management within captive
populations
understanding the risks associated with reintroducing parasite-naïve animals into
their natural environment
25 Chapter 1 - Introduction
understanding the risks of introducing exotic parasites between populations during
translocation and reintroduction programs
Identifying parasite fauna existing in the natural environment which may become
pathogenic within the host if/when exposed to environmental stressors.
These goals are addressed within the thesis in the following ways:
Chapter 2 details the general research methods utilized throughout the project.
Chapter 3 identifies the prevalence and diversity of parasites within wild and captive populations, whilst ascertaining significant effects of host sex and age, and environmental conditions of season and geographical region.
Chapters 4, 5 and 6 address specific parasite threats. Identification through molecular characterisation will allow species identification and an understanding of species distribution among hosts and populations. These methods also assist in identifying any health risks posed to either the host or surrounding human communities within both captive and wild environments.
Chapter 7 discusses the main findings with reference to the goals identified in Chapter 1.
26 Chapter 2 – General materials and methods
Chapter 2
General materials and methods
27 Chapter 2 – General materials and methods
2.1. Study design
A parasitological study was conducted on the African painted dog (Lycaon pictus) from both captive and wild populations. Collaborations were established with three captive animal facilities and three in situ conservation groups within Africa. The captive populations were housed in a range of environments including a free range savannah, zoo exhibit style and a rehabilitation/breeding centre. The wild populations were situated in a range of geographic locations within Africa. This range of facilities and locations was chosen in order to get a broad sample base from which variations in parasite prevalence and diversity may be identified.
These collaborations were crucial to the success of this project, as they allowed for continual sampling to occur from a range of environments. These associations also provided the opportunity for additional sampling during radio collaring and/or non-related veterinary events, whereby skin and blood samples could be obtained along with faecal samples. The majority of samples were collected during project field trips, however, some samples were collected by collaborators in the field during their own monitoring season.
Sampling was conducted over the three years of the project (2007-2009) with the exception of samples from Zimbabwe which had been collected previously in 2006. Most populations were sampled on multiple occasions during the study period. This sampling protocol was aimed at achieving longitudinal data from a range of environments in order to obtain a detailed baseline from which comparisons could be made.
28 Chapter 2 – General materials and methods
2.2 Captive populations
The captive populations were located at Monarto Zoo in South Australia, Perth Zoo in
Western Australia (Figure 2.1) and DeWildt Wildlife Trust in South Africa (Figure 2.5).
= Perth Zoo, Western Australia
= Monarto zoo, South Australia
Figure 2.1 Location of painted dog study sites within Australia.
2.2.2 Perth Zoo
Perth Zoo is a traditional zoo exhibiting animals in enclosures designed to be similar to the wild environment. The facility had a painted dog population of 17 animals: 12 males which were in the on-display exhibit and five females which were kept separately off-exhibit to prevent unplanned breeding. The on-display exhibit was a large sandy area (1550 m2) with large trees for shade and a small pond water feature (Figure 2.2). The off-exhibit area was smaller (480 m2) but also sandy with large trees for shade. All animals were given
29 Chapter 2 – General materials and methods ivermectin monthly as a heartworm prophylaxis. Praziquantel had previously been given as a preventative treatment for Taeniidae infections but medication with this drug had been halted a year before this project began. The painted dog diet consisted mainly of horse meat and the occasional sheep carcass which had been previously frozen. The three eldest animals were captive born and originated from DeWildt Wildlife Trust in South Africa.
The remaining 14 animals were the result of two litters born at Perth zoo. Samples were collected from both male and female exhibits annually over the three years prior to the monthly ivermectin treatment in November 2007, 2008 and 2009. A total of 43 faecal samples were collected and analyzed from the 17 animals over the three year period. Data collected annually were used to make comparisons within that population, however, data from 2007 only were used when making comparisons between populations to avoid including multiple samples from the same animal.
Figure 2.2 Painted dog exhibit at Perth Zoo showing the water feature and animals resting in the shade.
30 Chapter 2 – General materials and methods
2.2.3 Monarto Zoo
Monarto zoo is an open range safari style zoo located in South Australia. The facility had a total of 33 animals: 20 males which were in the on-display exhibit and 13 females which were kept separately off-exhibit to prevent unplanned breeding. The on-display exhibit area was a large (8 km2) open savannah style which visitors drove through on zoo buses
(Figure 2.3). The off-exhibit was a much smaller sandy area of approximately 500 m2.
Regular anthelmintic treatments were given to prevent parasitic infections however actual the anthelmintics used is unknown. The painted dog diet consisted mainly of kangaroo and horse meat which had been previously frozen. The three eldest animals originated from
DeWildt Wildlife Trust with the remaining animals being the result of litters born at the zoo. Faecal samples were collected from this facility once in May 2008. It is not known how recently anthelmintic treatment had occurred prior to sample collection. A total of 34 faecal samples were collected randomly by keepers during routine cleaning of enclosures.
Figure 2.3 Painted dog exhibit at Monarto zoo showing the animals in the large fenced enclosure.
31 Chapter 2 – General materials and methods
2.2.3 DeWildt Wildlife Trust
DeWildt Wildlife Trust is a breeding and rehabilitation centre for cheetah and African painted dogs located in Pretoria, South Africa. The facility had approximately 80 African painted dogs which were housed in up to 25 different enclosures. Enclosures held between one and six animals made up of various mixes depending on compatibility of animals and breeding requirements. Enclosures were of varying sizes, ranging from approximately 500 m2 to 1,500 m2, mostly grass covered and with trees for shade (Figure 2.4). Animals were treated with fenbendazole every four months as a preventative treatment for roundworm, hookworm and tapeworm. Diet consisted mainly of previously frozen whole chickens and horse meat with Iams dry dog food. Some animals originated from the wild having been translocated from livestock farms where they were at risk of being shot. The remaining population was the result of litters born at the facility. Samples were collected from this facility once in December 2007, which unfortunately was just after the quarterly anthelmintic treatment with fenbendazole.
Figure 2.4 Painted dog enclosure at DeWildt Wildlife Trust showing grassy and shady environment.
32 Chapter 2 – General materials and methods
2.3 Wild populations
The wild populations were located in South Luangwa National Park, Zambia, Nyae Nyae
Conservancy, Namibia and Hwange National Park, Zimbabwe (Figure 2.5).
= South Luangwa National Park, Zambia
= Hwange National park, Zimbabwe
= Nyae Nyae Conservancy, Namibia
DeWildt Wildlife Trust, South Africa
Figure 2.5 Locations of the painted dog study populations within Africa.
2.3.1 South Luangwa National Park – Zambia
Zambia is a land-locked country situated in central sub-Saharan Africa (Figure 2.5). South
Luangwa National Park is situated at the tail end of the Great Rift Valley and has an area of 9,050 km2. It is the second largest park in Zambia having been officially proclaimed in
1972 mainly in order to conserve the endemic Thornicroft’s giraffe (Giraffa camelopardalis thornicroftii). The Luangwa River acts as the eastern border of the park and is home to large populations of hippopotamus and crocodiles. The park has
33 Chapter 2 – General materials and methods populations of lion, spotted hyaena, leopard and various game animals. The vegetation of the park is a mosaic of mopane, miombo woodland, acacia and grassland (Figure 2.6).
There are two main seasons within Zambia, the dry season from May to November and the wet season from December to April.
Figure 2.6 South Luangwa National Park, Zambia. Open grassland area with acacia and mopane woodland in the background, which is typical of the habitat frequented by painted dog populations.
The population of African painted dogs within South Luangwa National Park is estimated at 200 (pers comm. E Droge, Zambian Carnivore Project). Field trips were conducted in collaboration with the Zambian Carnivore Project, a conservation group based in South
Luangwa National Park. Field agents from this project continually monitor populations of the African painted dog and other carnivores in order to conserve these species and their habitats. Samples were collected during field trips in October 2007, June 2008 and May
2009 with occasional sampling between field trips by Zambian Carnivore Project staff
34 Chapter 2 – General materials and methods during their monitoring periods of painted dog packs in and around the national park.
Where possible a GPS radio collar was placed on an individual within a pack in order to follow pack movements and ascertain roaming areas. This greatly increased the chances of locating packs and collecting faecal samples for this project.
2.3.2 Nyae Nyae Conservancy – Namibia
The Nyae Nyae Conservancy is situated in the north eastern corner of Namibia east of
Tsumkwe district (Figure 2.5). It is not a national park but a conservancy area for some of the last remaining San Bushmen, of the Ju’\Hoansi group. The area is approximately 8,900 km2 and contains a population c.3,000 of predominantly San Bushmen who are traditional hunter gatherers. The area has populations of hyaena, leopard and a small population of lion, along with various game animals. The habitat is semi-arid savannah with no perennial surface water (Figure 2.7), therefore wildlife are reliant on the few water holes existing throughout the dry season of April – October. A wet season exists from November to
March.
Figure 2.7 Nyae Nyae Conservancy, Namibia. One of the few sandy roads available to use, surrounded by thick grass and acacia trees.
35 Chapter 2 – General materials and methods
Apparently 75 painted dogs are found in the Tsumkwe area (Lines, 2009). Field trips were conducted in collaboration with the Wild Dog Project a conservation group conceived in
2002 by the Namibian Nature Foundation in response to a growth in local human/painted dog conflict. The main aim of the Wild Dog Project is to increase the understanding of interactions between African wild dogs and humans and finding ways of mitigating conflict and persecution (www.nnf.org.na/wilddogproject.htm). Samples were collected during a field trip in July 2008 in conjunction with the Wild Dog Projects own monitoring period of painted dog packs in the area. Additional sampling was conducted throughout the monitoring seasons of 2007 and 2008 by Wild Dog Project staff. Some packs had an individual fitted with a GPS collar, therefore radio-tracking was possible. However, locating packs within this area was difficult even using telemetry as the flat terrain greatly reduced signal range and there were minimal roads available to use.
2.3.3 Hwange National Park – Zimbabwe
Zimbabwe is located just below Zambia and is also a land-locked country (Figure 2.5).
Hwange National Park is Zimbabwe’s premier park and is situated in the north east corner of Zimbabwe, bordering Botswana. The park has populations of lion, spotted hyaena, leopard and various game animals. The vegetation of the area is a mosaic of miombo woodland, acacia and open vlei areas (Figure 2.8). Seasons are similar to Zambia with a dry season from May to November and a wet season from December to April.
36 Chapter 2 – General materials and methods
Figure 2.8 Game managed area of Hwange National Park, Zimbabwe. Open area with miombo woodland and acacia in the background, typical for painted dog habitat.
A field trip was conducted in May 2009, in collaboration with the Painted Dog
Conservation group which continually monitors populations of painted dogs in and around adjacent game managed areas of Hwange National Park. Some packs had an individual with a GPS collar, therefore radio-tracking was possible, however during this field trip no painted dog packs were located. Although no samples were collected during this time faecal samples had been stored from previous collections of which a portion collected in
April 2006 were made available for this study.
2.4 Sampling methodology
The majority of samples obtained for this project were faecal samples. This is a non- invasive method of obtaining biological data from wild animals and has been used for several previous parasitological studies on wildlife (Muller-Graf, 1995; Marathe et al.,
37 Chapter 2 – General materials and methods
2002; Engh et al., 2003; Smith and Kok, 2006). Non-invasive methods are particularly useful when dealing with endangered animals. Faecal samples can provide information on many parasites inhabiting the gastro-intestinal tract including helminths and protozoans.
Additionally, the application of molecular tools increases the information that can be obtained from these samples.
2.4.1 Ethics and permits
Animal ethics approval was obtained from Murdoch University Animal Ethics Committee
(permit number R2087/07) for the collection of samples including faeces, blood and ectoparasites from all captive and wild populations of the African painted dog involved in this study. Additionally the project obtained separate ethics approval from Perth
Zoological Parks Authority Animal Research and Ethics Committee (Project number,
2007-18; reference ZA/3149025776) for the collection of samples from the painted dog population at that facility.
Permits were obtained from the Zambian Wildlife Authority to conduct research on parasites of African wild dogs within South Luangwa National Park and adjacent Game
Management Areas. Permits were also obtained from the Ministry of Environment and
Tourism to conduct research and collect samples from the African painted dog populations in the Kavango and Caprivi regions of Namibia (Permit number 1297/2008). Government permits were not needed for Zimbabwe as faecal samples obtained had been collected previously by other researchers with the required documentation.
38 Chapter 2 – General materials and methods
2.4.2 Locating packs
Conducting studies on wildlife can be logistically difficult as finding and tracking animals within the wild environment is often challenging. The African painted dog has a large roaming area (>2,000 km2) and is particularly hard to visually locate due to the colour and pattern of each animals coat, which act as excellent camouflage. During the day, packs are inactive and are usually resting under trees or scrub and are difficult to locate. Radio tracking was therefore crucial to locate packs on any given day. Most packs within the study population had at least one animal radio-collared, which was usually sufficient to locate the rest of the pack. Radio-tracking was most successful when the packs were on the move as there was more chance they would move into the main game area and within telemetry range. This was usually when the packs were hunting which occurs in the morning and evening. Tracking in the morning was usually from 5am to 11am and in the afternoon from 3pm to 8pm, however, if it appeared the packs had moved from the vicinity of base-camp it was necessary to conduct longer searches, whereby the entire day was used for tracking. Occasionally this also required several days camping in the bush to continue the search in that area. On occasion a light aircraft was used to radio-track from the air which enabled the search grid to be greatly expanded.
When the packs were located, they were identified by compiled indentikits. Coat patterns are unique for each animal and are used as a means of identification. Animals therefore had both left and right sides of their torso photographed. Identification numbers were allocated to each animal within each pack and used for later identification in the field (Figure 2.9).
39 Chapter 2 – General materials and methods
Figure 2.9 The left and right side views of an individual painted dog from the Katete pack in Zambia. ID number P3 0308.
2.4.3 Sample collection
Sample collection in the wild environment involved locating and following packs and picking up faecal samples as dogs defecated. Faecal samples were placed in a ziplock bag and kept in a cooler box until return to camp. On return samples were placed into 2 x 10 ml centrifuge tubes and fixed in 70% ethanol and 10% formalin. Tubes were labelled with date, place collected, pack name and where possible individual animal identification. Many times it was not possible to identify individual animals due to the fast movements of animals as they rouse for a hunt or to interference from safari vehicles. Pack identification however, was usually obtained. During field trips three animals were anaesthetised in order to place a radio-collar, and in this case it was possible to obtain blood samples, check for ectoparasites and obtain faecal samples direct from the animal. Samples of blood were stored on FTA cards and a smear placed on a microscope slide, while ectoparasites were placed in 70% ethanol.
40 Chapter 2 – General materials and methods
Sample collection within the captive environment involved walking through enclosures and collecting faecal samples from the ground. Individual animal information was therefore not possible in most cases. At Perth zoo however, it was possible to get individual samples with the use of non-toxic plastic beads to act as faecal markers for individual dogs. With the help of keepers all animals were fed meat parcels (horsemeat) which had had coloured plastic markers (1 tsp) inserted into a pocket cut into the meat.
Animals were brought into the night quarters where they could be separated, identified and handfed the parcel of meat. Colours given to each animal was recorded in order to match scat samples collected in the next 24-48 hours. This method has been used with success in several studies on both wild and domestic animals (Delahay et al., 2000; Rolfe et al., 2002;
Staniland, 2002; Hernot et al., 2005).
2.4.4 Sample movement
The appropriate permits were obtained to export samples from Africa to Australia. A permit (number 73453) was obtained from Ministry of Environment and Tourism for samples sent from Namibia. Permits (numbers not given) were obtained from the
Department of Veterinary and Livestock Development for each shipment of samples sent from Zambia.
AQIS permits to import fixed faecal samples into Australia were not required providing specimens were preserved in either 70% ethanol or 10% formalin and containers were sealed and packaged correctly. This ensured all pathogens were killed and the risk of unforseen leakage was contained. Samples were stored in 10 ml centrifuge tubes fixed in
41 Chapter 2 – General materials and methods the appropriate preservative (70% ethanol or 10% formalin). These tubes were then wrapped in absorbent cotton material and placed inside two plastic coverings. These were then boxed and sent with copies of the appropriate export and import documentation for each country. All packages were sent through international shipping companies as
‘dangerous goods in accepted quantities’ packages to Murdoch University.
2.5 Parasitological techniques
Analysis of fresh faecal samples was preferred as parasite ova are more readily observed under microscopy, however, for quarantine reasons samples had to be preserved in a fixative. Faecal samples fixed in 10% formalin (2 parts faeces, 8 parts formalin) were deemed the preferred fixative for microscopy (Foreyt, 2001). Samples fixed in 70% ethanol were used for molecular characterisation.
2.5.1 Microscopy; qualitative analysis
Identification of parasite ova from faecal samples was made on size and morphology with reference to Foreyt (2001) (Figure 2.10). The coccidians observed were unable to be differentiated on size alone and as samples were preserved in 10% formalin oocyts, were not able to be sporulated for additional morphological information. Additionally, carnivores are commonly known to exhibit spurious coccidian infections originating from ingested prey items further complicating identification (Bowman et al., 2003). However, whilst it was recognized that some observations of coccidia may not be true infections, it was impossible to ascertain which were not spurious, therefore all positive samples were
42 Chapter 2 – General materials and methods included in the prevalence data. In an attempt to observe all parasites existing within each sample three techniques were employed: Malachite green stain, zinc sulphate flotation and sodium nitrate flotation.
Figure 2.10 Parasite ova of taeniid spp. and Giardia spp. cysts observed during microscopy analysis of painted dog faecal samples. Morphology and size are substantially different between the two genera, allowing for unambiguous identification.
The malachite green stain was based on a simple faecal smear but with a drop of 5% malachite green added which enabled parasite ova, particularly Cryptosporidium oocysts, to be more readily observed (Elliott et al., 1999). Flotation techniques are commonly used to recover parasite eggs and oocysts from faeces and are designed around differences in specific gravity of parasite ova and faecal debris within specific flotation media (Bowman et al., 2003). Most parasitic stages float at a specific gravity of 1.2 to 1.3 whilst faecal debris will sink (Foreyt, 2001). As some parasite ova are heavier (eg. Trichuris sp. ova) and formalin fixing can alter the normal buoyancy of eggs, two flotation media were used, sodium nitrate with a specific gravity of 1.27 and zinc sulphate with a specific gravity of
1.18 (pers comm. A. Elliott). Sodium nitrate was used with the commercially available
Faecalyzer® tubes as gravitational force alone was sufficient for eggs to float within this 43 Chapter 2 – General materials and methods medium (Bowman et al., 2003). A small amount of faecal sample was placed into the tube which was then filled with sodium nitrate and left for 10 minutes. A coverslip placed on top of the tube collected the parasite ova which had floated to the top and was then used for microscopy. Zinc sulphate was used for the remaining sample with 2 g of faeces placed into a 10 ml centrifuge tube, emulsified in the flotation medium and centrifuged at 2,000 rpm for five minutes. This method concentrated all parasite ova into the top layer of the tube where a wire loop was used to collect 5 drops of fluid from the meniscus and placed onto a microscope slide for analysis. Three slides containing blood smears were to be analysed for the presence of haemoparasites such as Babesia spp. using microscopy, however, before this could be done slides were lost. Results for ectoparasites obtained during the study period were not included in this thesis due to the very small sample size.
2.5.2 Microscopy; quantitative analysis
Quantitative analysis was undertaken by calculating eggs per gram (EPG) of faeces.
Calculating EPG is generally done using a McMaster counting chamber (Foreyt, 2001;
Bowman et al., 2003). The zinc sulphate technique used in this project involved a known amount of faeces and fluid for each test but the wire loop collection method inhibited use of a McMaster chamber, therefore alternate calculation methods were devised (pers comm.
R. Dobson). As outlined above, five wire loop drops were placed onto a slide and all parasite ova and cysts under the coverslip were counted. The volume of the fluid placed onto the slide was weighed and found to be 0.035 g, coming from the meniscus of the 10 ml tube which was estimated at 0.1 ml. Therefore 1/3 of floated ova and cysts were
44 Chapter 2 – General materials and methods counted. To obtain EPG the total was multiplied by three (for total meniscus count) and then divided by 2 (as 2 g of faeces was in each 10ml tube).
2.5.3 Molecular characterisation
As species identification for many parasites is not possible from parasite ova, molecular techniques were employed to characterise these to species level. As these techniques are time consuming and expensive only parasite genera considered important from a zoonotic or pathogenic perspective were chosen. Molecular characterisation was therefore conducted on faecal samples containing taeniid ova, hookworm ova and Giardia cysts.
Full methodologies for these are found in Chapters 4, 5 and 6. Five blood samples on FTA cards were sent to a laboratory in South Africa for molecular studies on haemoparasites such as Babesia spp. but results have not yet been received. These same FTA card blood samples were tested for the presence of Trypanosoma spp. using molecular methods. All samples were negative and as there were so few samples, results were not included in the main body of this thesis.
45 Chapter 3 – Diversity and prevalence of…..
Chapter 3
Diversity and prevalence of gastrointestinal parasite fauna within captive and wild populations of the African painted dog
46 Chapter 3 – Diversity and prevalence of…..
3.1 Introduction
There are at least as many species of parasites as there are free-living organisms, yet except for humans and a small number of domesticated plants and animals, little is known about the diversity and prevalence of parasites existing within host populations (Altizer et al.,
2003a; Mathews et al., 2006; Smith et al., 2009a). It is widely acknowledged that parasites have the ability to regulate host populations through their ability to influence host mortality, morbidity and fecundity (May and Anderson, 1978; Scott, 1988; McCallum and
Dobson, 1995; Hudson et al., 1998). Parasites may also mediate predatory and competitive interactions, host immunity, host genetic diversity and host behaviour (Anderson, 1972;
Carroll and Grove, 1985; Temple, 1987; Altizer et al., 2003b; Maillard and Gonzalez,
2006; Barnes et al., 2007). These factors are important processes within ecosystems and highlight the significance of parasitism within host populations. To add to these complex interactions, the effects of outside stressors such as habitat destruction and human encroachment are important influences which can easily disrupt the natural balance of many host/parasite relationships (McCallum and Dobson, 1995; McCallum and Dobson,
2002; Gillespie et al., 2005).
The increasing recognition of parasites and their interactions within wildlife hosts has resulted in additional research, yet comprehensive baseline data are still lacking for many species of wildlife (Daszak et al., 2000; Applebee et al., 2005; Deredec and Courchamp,
2006; Penzhorn, 2006; Thompson et al., 2010). Most studies on parasitism in wildlife focus either on understanding the life cycle and pathogenesis of a single parasite species or taking a ‘one-off’ snapshot of the parasite community existing within a particular host population. While such studies are useful starting points, of greater benefit would be
47 Chapter 3 – Diversity and prevalence of….. longitudinal studies of several populations in various geographical regions. This detailing of temporal and spatial variation of parasitic infections within the natural environment would provide a baseline from which potential pathogenic changes could be identified
(Bjork et al., 2000). Pathogenic effects may originate from introduced exotic parasites for which host populations have not developed any level of immunity, for example, the introduction of rabies and canine distemper virus from domestic dog populations into
African lion (Panthera leo) and African painted dog (Lycaon pictus) populations
(Alexander and Appel, 1994; Kat et al., 1995; Cunningham, 1996; Daszak et al., 2000).
Likewise, enzootic parasites which within a healthy population cause little pathogenicity could give rise to clinical disease in populations experiencing stressors such as drought, overcrowding due to habitat destruction or human encroachment (McCallum and Dobson,
2002; Penzhorn, 2006; Munson et al., 2008). Without good baseline data of parasitism within natural environments these events would be difficult to identify or predict. The lack of good baseline data is in large part due to the difficulties involved in sampling wild populations. Locating study animals, obtaining individual identifications and obtaining samples is time consuming and logistically difficult.
The African painted dog is a highly endangered carnivore with approximately 3,000 animals remaining in the wild (IUCN, 2010). These individuals exist in small fragmented populations which are vulnerable to stochastic disease outbreaks, leading to local extinctions as already observed in the Serengeti ecosystem (Kat et al., 1996; Sillero-Zubiri et al., 2004). It is therefore essential for the future conservation of this animal to gain a broad understanding of threatening processes, such as parasitism, to which this animal is routinely exposed.
48 Chapter 3 – Diversity and prevalence of…..
This is the first longitudinal parasite survey of the African painted dog and one of few existing for any wild species. This project was fortunate in being able to collaborate with three in situ conservation groups in Zambia, Namibia and Zimbabwe, which were constantly monitoring painted dog packs within their study area. This enabled comprehensive sample collection from known individuals and packs over various geographic regions. By sampling over a period of time in various geographic regions it was hoped to gain insight into the population dynamics of parasitism within a wild and endangered carnivore.
The aim of this study was to determine the prevalence and diversity of gastrointestinal (GI) parasites within captive and wild populations of the African painted dog and relate measures of parasitism to intrinsic factors such as host age and sex, and extrinsic factors such as location and season. The following hypotheses were tested: 1) levels of parasitism are markedly different between captive and wild populations; 2) levels of parasitism are greater in the wet season than in the dry season in the wild; 3) levels of parasitism are greater in younger animals and 4) there are geographical differences in levels of parasitism between wild populations.
3.2 Materials and methods
3.2.1 Sampling protocol
Faecal samples were obtained from three wild populations and three captive populations of the African painted dog over a four year period, 2006 – 2009. Chapter 2 gives detailed descriptions of populations sampled. A total of 128 samples were collected from a possible
49 Chapter 3 – Diversity and prevalence of…..
83 individual animals within the wild populations and 104 samples from 130 individual animals within the captive populations (Table 3.1)
Table 3.1 Number of faecal samples obtained from all captive and wild populations during the study period.
Population Sampling year Total Individual
samples animals
2006 2007 2008 2009
Wild populations
Zambia - 11 44 18 73 43
Namibia - 19 10 - 29 28
Zimbabwe 26 - - - 26 12
Total 26 30 54 18 128 83
Captive populations
Perth - 16 14 13 43 17
Monarto - - 34 - 34 33
DeWildt - 27 - - 27 80
Total 0 43 48 13 104 130
Collection of samples from wild populations was conducted during field monitoring of packs within the study area. Faecal samples were collected soon after being deposited and individual animal information was obtained where possible. Within Zambia, most samples were collected during the periods of November to December 2007, May to June 2008 and
50 Chapter 3 – Diversity and prevalence of…..
May to June 2009, however, a small proportion were collected throughout the year by field collaborators. Within Namibia, most samples were collected during August to November
2007 and May to November 2008 by field collaborators. Within Zimbabwe, samples were collected in April 2006 and stored for later analysis.
Collection of samples from captive populations was conducted during cleaning of enclosures by zoo keepers. A single sampling episode was undertaken in December 2007 for the South African population and May 2008 for the South Australian population. These samples were obtained randomly from group enclosures. Sampling in Western Australia was conducted each year in November of 2007, 2008 and 2009. In Western Australia, sampling of individual hosts was made possible by spiking the animals’ meat with non- toxic plastic beads which allowed for identification on defecation (see Chapter 2).
Two grams of faecal matter from each sample were placed into two 10 ml centrifuge tubes containing 8 ml of either 10% formalin for subsequent microscopy analysis or 70% ethanol for molecular characterisation.
3.2.2 Parasite identification and quantification
See Chapter 2 for a full description of microscopy methods used. All parasite ova, cysts and larvae were recorded. Eggs and/or oocysts per gram (EPG) of faeces were calculated as described in Chapter 2 and results used for quantitative analyses. EPG values were not obtained for Spirometra spp. or Filaroides spp. as these were rare observations. Similarly,
EPG values were not obtained for Giardia spp. as it was found that cysts were especially
51 Chapter 3 – Diversity and prevalence of….. hard to observe in formalin fixed samples due to desiccation, leading to an under estimation of intensity.
3.2.3 Host and environmental variables
When age and sex of the host was known, individual data were used for comparisons. Ages of two years and under were defined as juvenile (n=9) and above 2 years were defined as adult (n=20). Nineteen samples were obtained from identified males and 13 from females.
All wild sample sites had distinctive wet and dry seasons which were also used for comparisons. Wet season samples (n=28) were from December through to March and dry season samples (n=62) from April through to November.
3.2.4 Data analysis
This study examined the differences in parasite prevalence and diversity, intensity of parasite infection and parasite infracommunity composition within and between captive and wild populations of the African painted dog.
3.2.4.1 Descriptors used Descriptors used to quantify parasitism within this study followed Bush et al. (1997) and
Poulin (1993) as follows:
Parasite load (N) is the total number of parasites, of all species, in a single infected
host, i.e. the number of individual parasites in an infracommunity. Parasite load
was measured by the total EPG.
52 Chapter 3 – Diversity and prevalence of…..
Prevalence is the percentage or proportion of hosts infected with one or more
individuals of a particular parasite species or taxonomic group.
Diversity is the number of species of parasites present within specific individuals
and/or groups of hosts. Diversity of parasites was measured by species richness (S)
and the Shannon-Wiener index of species evenness (H).
Infracommunity composition is the number and intensity of species in an individual
host.
Parasite aggregation within host populations is defined as when most hosts harbour
few or no parasites, while only few are heavily infected. Aggregation was measured
by the index of discrepancy (D) using EPG data for a particular species.
3.2.4.2 Levels of testing Levels of parasitism were firstly tested between wild and captive groups for significant differences. The data from wild populations were then analysed at the pack and population
(all packs within a national park) level and related to intrinsic factors such as host age and sex, and extrinsic factors such as geographic location and season (see Table 3.2). For many comparisons sufficiently large sample sizes could only be obtained by pooling data over age, sex and seasonal classes, or over different packs or populations. Data from year 1
(2007) of the Perth Zoo captive population were pooled with the other two captive populations for comparison with wild populations. In wild populations, data were pooled over time when making comparisons as it was found that the composition of packs varied significantly from season to season with many deaths recorded, consequently duplicate sampling of individuals was extremely rare. Known duplicates obtained within the same sampling period were discarded before performing statistical analysis.
53 Chapter 3 – Diversity and prevalence of…..
Table 3.2 A hierarchical list of comparisons made between host groups with descriptions of the data used at each level.
Comparison Data used for comparison
Between wild and captive populations Data from the three captive populations were pooled and compared against pooled data obtained from the three wild populations.
Among packs Data from two packs within the Zambian population were pooled over all age, sex and season classes.
Among populations in different geographic Data from Zambia, Namibia and Zimbabwe regions in the wild were pooled over all age, sex and seasonal classes in each population.
Among wet and dry seasons in the wild Data were pooled over geographic regions, age and sex and compared between wet and dry season.
Among host sex classes in the wild Data were pooled over geographic regions, season and age and compared between males and females.
Among host age classes in the wild Data were pooled over all geographic regions, season and sex and compared between juveniles and adults.
54 Chapter 3 – Diversity and prevalence of…..
3.2.4.3 Statistical analysis Prevalences of infection were expressed as a percentage of positive samples found with
95% confidence intervals calculated assuming a binomial distribution, using the software
Quantitative Parasitology 3.0 (Rozsa et al., 2000). Differences in prevalences between groups were tested using the Fisher’s exact test.
One way analysis of variances (ANOVA’s) were used to compare species richness (S), species diversity (H) and parasite load (N) among groups of hosts with the software JMP
4.0 (SAS Institute Inc; www.sas.com).
Similarities in parasite species infracommunity composition among individual hosts were estimated from EPG data using the Bray-Curtis coefficient. Multidimensional scaling plots were used to represent these data where a stress value of less than 0.2 was taken to indicate reasonable representation of rank similarities by the ordination plot (Clarke, 1993). The significance of differences in parasite species composition between groups of hosts was tested by a permutation procedure applied to the pair-wise similarity matrix (one-way
ANOSIM) using the computer package PRIMER 6.0 (Clarke and Gorley, 2006). The contribution of individual parasite species to dissimilarities between variables was assessed by averaging the Bray-Curtis similarity term for each species over all pair-wise variable combinations using SIMPER procedure in PRIMER 6.0. Parasite aggregation within hosts was tested using the index of discrepancy, (D) as per Poulin, (1993) with the software
Quantitative Parasitology 3.0 (Rozsa et al., 2000).
55 Chapter 3 – Diversity and prevalence of…..
3.3 Results
3.3.1 Variation between captive and wild populations
Table 3.3 displays the diversity of GI parasites within all captive and wild populations sampled. Overall prevalence of infection (i.e. infection with any species of parasite) was significantly greater in wild than in captive populations (Fisher’s exact test, P<0.0001).
The wild population also had a greater parasite load (N; F=503.1, P<0.0001), species richness (S; F=213.3, P<0.0001)) and species evenness (H; F=80.9, P<0.0001), (Figure
3.1)
9 8 7 6 5 Captive 4 Wild 3 Mean value 2 1 0 -1 NSH Measures of parasitism
Figure 3.1 Parasite load (N), species richness (S) and species evenness (H) in captive and wild populations of the African painted dog.
56 Chapter 3 – Diversity and prevalence of…..
Table 3.3 The prevalence (with 95% confidence intervals in parentheses) and diversity of GI parasites detected in faecal samples from all captive and wild populations of the African painted dog.
Population Total parasite Taxon prevalence (%) prevalence
(%) Taeniid Ancylostoma Spirometra Giardia Coccidia Sarcocystis Filaroides
Captive 15 0 0 0.8 14 0 0 0 n=130 (0.04 - 4) (6 – 16)
Wild 99 32 32 2 26 13 99 2.4 n=83 (22 – 42) (23 – 43) (0.07 – 6) (18 – 37) (8 – 24) (94 – 100) (0.4 – 8)
57 Chapter 3 – Diversity and prevalence of…..
3.3.2 Variation between packs
Two packs (Katete and Kaingo) within the Zambian study population were sampled sufficiently to enable comparisons to be made on parasite prevalence, parasite load, diversity and infracommunity composition. Table 3.4 displays the prevalences of all GI parasites observed in the Katete and Kaingo packs of South Luangwa National Park,
Zambia. The Katete pack had a significantly greater prevalence of taeniid spp. (Fisher’s exact test, P=0.005), Ancylostoma spp. (Fisher’s exact test, P=0.002) and Coccidia
(Fisher’s exact test, P=0.005) than that observed in the Kaingo pack. The Katete pack also had a greater parasite load (N; F=28.4, P<0.0001), species richness (S; F=34.8, P<0.0001) and species evenness (H; F=41.9, P<0.0001) (Figure 3.2).
Table 3.4 Prevalence (with 95% confidence intervals in parentheses) of GI parasites detected in faecal samples from two packs within the Zambian study population.
Pack ID Taxon prevalence (%)
Taeniid Ancylostoma Spirometra Giardia Coccidia Sarcocystis Filaroides
Katete 50 58 8 8 50 100 16
(n=12) (24-76) (29-82) (0.4-37) (0.4-37) (24-76) (76-100) (3-46)
Kaingo 0 0 0 46 0 100 0
(n=13) (22-74) (77-100)
P value 0.005 0.002 0.5 0.07 0.005 1.00 0.2
58 Chapter 3 – Diversity and prevalence of…..
14 12
10
e 8 Katete 6 Kaingo
Mean valu Mean 4
2 0 NSH -2 Measures of parasitism
Figure 3.2 Parasite load (N), species richness (S) and species evenness (H) in two packs within the Zambian study population.
Infracommunity composition was also found to be significantly different between painted dogs in the two packs (ANOSIM, R=0.42, P=0.001). This can be clearly seen in the two- dimensional ordination plot of Bray-Curtis similarity coefficients of parasite infracommunity composition (Figure 3.3).
Figure 3.3 A multidimensional scaling plot of data from two African painted dog packs within the Zambian population based on Bray-Curtis similarity coefficients of parasite infracommunity composition.
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3.3.3 Variation among different geographic locations
Sampling was conducted in three geographic locations - Zambia, Namibia and Zimbabwe.
Populations in these locations were tested for differences between parasite prevalence, parasite load, diversity and infracommunity composition. Coccidia were significantly less prevalent in Namibia when compared with Zambia (Fisher’s exact test, P=0.009) and
Zimbabwe (Fisher’s exact test, P=0.02), however, no significant differences were found in the prevalence of other parasite species or in the overall prevalence of GI parasite infections (Table 3.5).
A significant difference in parasite load (N; F=3.2, P=0.04), but not species richness (S;
F=1.1, P=0.3) or species evenness (H; F=0.9, P=0.5), was observed among populations
(Figure 3.4). There were, however, no significant differences in parasite infracommunity composition among populations (ANOSIM R=0.06, P=0.08).
10 9 8
s 7 6 Zambia 5 Namibia 4 Zimbabwe Mean value Mean 3 2 1 0 NSH Measures of parasitism
Figure 3.4 Parasite load (N), species richness (S) and species evenness (H) in three wild populations of the African painted dog.
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Table 3.5 The overall prevalence (with 95% confidence intervals in parentheses) and diversity of GI parasites detected in faecal samples from three wild populations - Zambia, Zimbabwe and Namibia.
Population Total Taxon prevalence (%)
prevalence Taeniid Ancylostoma Spirometra Giardia Coccidia Sarcocystis Filaroides (%)
Zambia n=43 100 35 33 2 30 21 100 5
(91-100) (22-50) (19-48) (0.1-13) (18-45) (11-36) (91-100) (0.8-16)
Namibia n=28 96 25 43 0 29 0 96 0
(83-100) (12-45) (26-62) (14-48) (83-100)
Zimbabwe n=12 100 33 8 0 8 25 100 0
(76-100) (12-63) (0.4-37) (0.4-37) (7-54) (76-100)
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3.3.4 Variation between different seasons
All study sites have definite seasonal variation with a wet and dry season. Table 3.6 displays the prevalence of GI parasites obtained from hosts during the wet and dry seasons pooled over populations from all geographic locations. A significantly greater prevalence was observed for Ancylostoma spp. (Fisher’s exact test, P=0.03) and taeniid spp. (Fisher’s exact test, P=0.005) during the wet season.
Table 3.6 Prevalence of the main GI parasites (with 95% confidence intervals in parentheses) detected in faecal samples from all wild populations in wet and dry seasons.
Season Taxon prevalence (%)
Taeniid Ancylostoma Giardia Coccidia Sarcocystis
Wet (n=28) 46 61 18 18 100
(28-65) (41-71) (7-36) (7-36) (88-100)
Dry (n=62) 23 27 26 19 98
(13-35) (18-40) (16-38) (11-31) (91-100
P-value 0.03 0.005 0.6 1.00 1.00
Parasite load (N; F=0.5, P=0.4) was not significantly different between seasons but a greater level of species richness (S; F=4.7, P=0.03) and species evenness (H; F=5.2,
P=0.05) was observed in the wet season (Figure 3.5).
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10 9 8
s 7 6 Wet 5 Dry 4 Mean value Mean 3 2 1 0 NSH Measures of parasitism
Figure 3.5 Parasite load (N), species richness (S) and species evenness (H) between wet and dry seasons in all wild populations of the painted dog.
Community composition was also found to be significantly different between seasons
(ANOSIM R=0.13, P=0.007) as displayed in Figure 3.6. This is shown in the two- dimensional ordination plot of Bray-Curtis similarity coefficients of parasite infracommunity composition among populations (Figure 3.6).
Figure 3.6 A multidimensional scaling plot of data from wet and dry environments of three wild populations based on Bray-Curtis similarity coefficients of parasite infracommunity. 63 Chapter 3 – Diversity and prevalence of…..
3.3.5 Variation between host age and sex
No significant relationships were identified between host sex and levels of parasite prevalence (Fisher’s exact test, P=0.3), parasite load (N; F=0.002, P=0.9), species richness
(S; F=1.6, P=0.2), species evenness (H; F= 0.9, P=0.3) and parasite infracommunity composition (ANOSIM R=0.16, P=0.09).
No significant relationships were identified between host age and levels of parasite prevalence (Fisher’s exact test, P=1.00), parasite load (N; F=1.2, P=0.3), species richness
(S; F=0.4, P=0.5), species evenness (H; F=1.1, P=0.9) and parasite infracommunity composition (ANOSIM R=0.01, P=0.5).
3.3.6 Parasite aggregation within hosts
Parasite species from which sufficient EPG data were obtained (Ancylostoma spp., taeniid spp., coccidia and Sarcocystis spp.) were tested for aggregation within the host populations of Zambia, Namibia and Zimbabwe. Aggregation of these parasites was observed within each population by the Index of Discrepancy (D) values. A value of 0 indicates an even distribution of counts across all hosts and a value of 1 indicates all parasites aggregated in a single host (Table 3.7).
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Table 3.7 Aggregation of parasite species within host populations in Zambia, Namibia and
Zimbabwe using the Index of Discrepancy values (D).
Ancylostoma Taeniid Coccidia Sarcocystis
Zambia 0.83 0.81 0.85 0.7
Namibia 0.8 0.84 - 0.72
Zimbabwe 0.85 0.7 0.8 0.51
3.4. Discussion
3.4.1 Parasite diversity
Overall, a total of seven GI parasite genera were observed in the African painted dog. Five of these genera have not been reported before in this host: Giardia, Spirometra,
Sarcocystis, Isospora and Filaroides.
Table 3.8 GI parasite genera observed in this study and in published literature.
GI parasite genera detected in this study GI parasite genera reported in published literature* Taeniid Taeniid Ancylostoma Ancylostoma Spirometra Ascarid (species undetermined) Giardia Isospora Sarcocystis Filaroides *Young et al., 1975; van Heerden et al., 1994, 1995.
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The most prevalent parasite genus observed in wild populations of dogs was Sarcocystis
(99%), followed by taeniids (32%), Ancylostoma (32%), Giardia (26.5%), Coccidia (13%),
Spirometra (2.4%) and Filaroides (2.4%). In contrast, only Giardia (14.5%) and
Spirometra (0.8%) were observed in the captive populations.
The high prevalence of Sarcocystis spp. sporocyst in faecal samples suggests that the painted dog is a natural definitive host for this organism. This finding is perhaps not surprising considering carnivores are known definitive hosts for species of parasite with transmission occurring through ingestion of infected prey. Species identification within the genus Sarcocystis was not made in this study but based on the prey items of the painted dog and known intermediate hosts, likely species can be suggested. Cosmopolitan species which have canids as the definitive host include S. arieticanis (sheep), S. capricanis (goat) and S. cruzi (cattle) and could all be potential sources of infection for the painted dog.
Species with intermediate hosts specific to Africa include S. nelsoni (puku and waterbuck),
S. melampi (impala), S. woodhousi (springbok, dik dik) and S. phacochoeri (warthog)
(Levine, 1986; Odening, 1986). While definitive hosts for these Sarcocystis species are unknown, the intermediate hosts are known prey items of the painted dog which could therefore be considered as a possible definitive host (Estes, 1967; Creel and Creel, 1995;
Hayward et al., 2006).
The only previous study reporting this parasite in the painted dog observed Sarcocystis- like organisms in the musculature and suggested that the painted dog was a natural intermediate host (Bwangamoi et al., 1993). Whilst carnivores acting as intermediate hosts for Sarcocystis is rare, schizonts of S. canis, which are normally only present in the
66 Chapter 3 – Diversity and prevalence of….. intermediate host have been identified in the tissues of domestic dogs (Dubey and Speer,
1991). Sarcocystis is rarely pathogenic to the definitive host, but acute infection in the intermediate host may cause extensive tissue damage and subsequent increased mortality and morbidity (Dubey et al., 1989; Bowman et al., 2003).
Taeniids and Ancylostoma spp. were found at the same prevalence of 32% within the wild populations, which is similar to a previous report of a wild population of the painted dog
(van Heerden et al., 1995). Taeniids are generally non-pathogenic to the definitive host but heavy infections may lead to possible intestinal obstruction (Foreyt, 2001). Infections with
Ancylostoma can be pathogenic, particularly to young and/or immunocompromised animals, and deaths due to ancylostomiasis have been recorded in a captive population of the painted dog (van Heerden et al., 1994; 1996).
Species of Giardia had not been observed in the African painted dog prior to this study, but this parasite genus is becoming increasingly recognised in populations of several wild host species (Graczyk et al., 2002; Gompper et al., 2003; Gillespie et al., 2005; Trout et al.,
2006; Thompson et al., 2009). The prevalence observed in this study indicates a substantial portion of animals in the wild are infected, with unknown clinical effects. This parasite does have the ability to cause sub-clinical disease, such as growth retardation in hosts suffering from poor nutrition, which may be of consequence to declining painted dog packs experiencing lowered hunting success (Astiazaran-Garcia et al., 2000; Courchamp et al., 2002).
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Whilst differentiation among the coccidians was not possible for most observations,
Isospora canis was identified on the basis of the large size of the oocysts, separating it from most other coccidians. This parasite is host specific to canids, indicating a true infection rather than a spurious observation of parasites from ingested prey species. Heavy infections can cause severe enteritis, particularly in pups (Bowman et al., 2003). Filaroides spp. and Spirometra spp. were only observed rarely in this study but these are the first reports for the painted dog. Spirometra was observed in both captive and wild populations, while Filaroides was observed only in wild populations.
3.4.2 Influence of geographic, seasonal and demographic factors
Within wild painted dogs there were some differences observed in prevalence and diversity of parasite species between packs, geographic populations and seasons, but overall a fairly consistent parasite community composition existed. Significant differences in parasite prevalence, diversity and infracommunity composition were observed between packs in
Zambia. This difference is likely to be a consequence of the social aspects of packs, such as close physical contact and ingestion of the same prey items which will result in minimal variation of parasite fauna within packs. Differences between packs however, will be maximised even if these variations arise from chance (stochastic) events, rather than underlying differences in animals or environment. At the population level the composition of parasite infracommunity did not differ significantly between dogs from Zambia,
Namibia and Zimbabwe. That is, the same types of parasite species were observed in all wild populations. There was however, a greater parasite load found in populations from
Zambia and Zimbabwe than in the Namibian population. This may be a reflection of
68 Chapter 3 – Diversity and prevalence of….. climate differences among geographic areas as Zambia and Zimbabwe have similar climates, whilst the study site located in Namibia is dryer with a desert-like environment outside the wet season.
Seasonal factors did appear to have an effect on parasite composition and load. The parasite composition of populations in the wet season displayed a greater abundance of
Ancylostoma spp. and taeniid spp. whilst populations in the dry season had a greater abundance of Sarcocystis spp. and coccidians. Moist conditions are favourable for the transmission of Ancylostoma spp. as it is beneficial for the survival of the infective larval stage hence, transmission rates between hosts are increased, explaining the higher abundance observed in the wet season. Whilst taeniid ova are extremely resilient to the environment, prolonged high temperature can reduce survivability and therefore transmission rates would be reduced in a hot, dry environment and increased in a cool, moist environment (Lawson and Gemmell, 1983).
Sex or age of the animal appeared not to have any effect on parasite load, parasite composition or general prevalence of any parasite species. The result for age was surprising as young animals are often more susceptible and therefore exhibit higher parasite loads (Bowman et al., 2003). This result may be a reflection of insufficient sampling of young animals, as samples were difficult to obtain from painted dog pups which remain at the den site for the first three months. Similar results have been reported, however, in prevalence studies on other species of wildlife (Muller-Graf et al., 1999; Bjork et al., 2000; Feliu et al., 2001). In particular, a study on lions in Tanzania infected with
Spirometra spp. found no relationship between sex or age and the mean number of parasite
69 Chapter 3 – Diversity and prevalence of….. species, although there was geographic variation (Muller-Graf et al., 1999). Additionally, studies on trematodes and their hedgehog host (Erinaceus europaeus) found no significant differences in intensities between host sex or age, but again environmental factors such as season have been shown to be significant (Feliu et al., 2001).
Aggregation of parasites within hosts was evident for all parasite species tested within this study. Aggregation has been commonly seen in wildlife populations, including painted dog competitor species such as African lion and spotted hyaena (Muller-Graf, 1995; Shaw et al., 1995; Engh et al., 2003). The aggregation of parasites within individual hosts can be due to several factors such as difference in prior history of exposure (young animals with undeveloped immune systems); difference in susceptibilities to pathogens,
(immunocompromised animal); or simply chance events of infection (Holt and Boulinier,
2005). Aggregation may well be beneficial to the host population as it is thought to stabilize the host-parasite dynamics (Holt and Boulinier, 2005).
3.4.3 Parasites of wild and captive populations
In all captive populations the diversity and prevalence of parasites was much reduced compared to wild populations. This was perhaps expected as captive facilities actively reduce parasitism through modification of diet (a lack of wild prey) and regular treatment with anthelmintics. The level of difference, however, was quite marked, with animals in captive facilities virtually parasite-free. This could be of significant consequence for animals marked for reintroduction programs as they may have insufficient immunity to withstand the challenge of a ‘natural’ parasite load in the wild. For example, dogs with
70 Chapter 3 – Diversity and prevalence of….. prior exposure to Ancylostoma spp. are able to build a protective immunity against later potentially pathogenic burdens, whereas immunologically naïve animals are highly susceptible to clinical disease (Carroll and Grove, 1985). In the long term, populations which remain parasite-free over several generations may exhibit an overall reduction in genetic diversity, in particular in the major histocompatibility complex (MHC) which plays an important role within the immune system. Studies have found parasite infections have a selective force on MHC diversity within the host, subsequently increasing diversity of this important region of the genome (Paterson et al., 1998; Wegner et al., 2003; Gouy de
Bellocq et al., 2008). An increased polymorphism of the MHC may ultimately increase the ability of the host to mount adequate immune responses to future parasitic infections and is therefore an important consideration in captive breeding populations.
3.4.4 Conclusions
In summary, this study has obtained comprehensive data on the prevalence and diversity of gastrointestinal parasites within the painted dog. Several parasites have been reported for the first time which demonstrates the paucity of information available for this endangered carnivore. Studies such as this are important to provide a detailed baseline from which future conservation programs may benefit. Identifying any departures from the ‘normal’ levels of parasitism may indicate threatening processes at play. This could then allow predictions and subsequent preventions for emerging diseases, as well as providing guidance for parasite control in captive breeding populations.
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Chapter 4
Molecular epidemiology of Giardia duodenalis in an endangered carnivore – the African painted dog
A form of this chapter has been published as:
A. Ash, A. Lymbery, J. Lemon, S. Vitali and R.C.A. Thompson (2010), Molecular epidemiology of Giardia duodenalis in an endangered carnivore – The African painted dog. Veterinary Parasitology, 174, 206-212.
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4.1 Introduction
The impact that parasites and other infectious agents have on wildlife has been increasingly recognized within conservation programs. Stressors such as human encroachment and habitat destruction are altering the incidence and effect that these pathogens have on wildlife populations, especially those endangered and under stress
(McCallum and Dobson, 1995; McCallum and Dobson, 2002; Wyatt et al., 2008; Smith et al., 2009a; Smith et al., 2009b). Habitat destruction results in reduced species ranges and increased interactions between populations, which in turn raises the risk of disease transmission between these populations (Scott, 1988; Lyles and Dobson, 1993). Perhaps of greater significance is human encroachment and the resultant increased interaction of humans and their domestic animals with co-habiting wildlife. Approximately 80% of domestic animal pathogens can infect wildlife (Cleaveland et al., 2001) so the risk of disease spillover into wild populations is potentially great.
Parasite species previously observed in the African painted dog have included the macroparasites Taenia sp., Ancylostoma caninum, Dipetalonema reconditum and Toxocara sp. (van Heerden, 1986; van Heerden et al., 1995), and protozoan parasites Babesia canis,
Hepatozoon sp. and Sarcocystis sp. (Colly and Nesbit, 1992; Bwangamoi et al., 1993;
Peirce et al., 1995; Penzhorn, 2006). To date, Giardia have not been recorded in the
African painted dog.
Giardia duodenalis (syn G. intestinalis; G. enterica) is a ubiquitous protozoan parasite found in a wide range of animals which can cause diarrhoea and ill thrift in a wide range of host species (Farthing et al., 1986; Thompson, 2004). Molecular characterisation of
73 Chapter 4 – Molecular epidemiology of…..
Giardia duodenalis isolates has identified seven genetically distinct genotypes which appear to be host specific (Thompson, 2000; Monis et al., 2009). These genotypes have been named assemblages A through to G. Of interest to this study are Assemblages C and
D which are specific to dogs and Assemblages A and B which affect humans, but are also found in a variety of other mammals. Assemblages A and B are thus of particular significance as they are considered potential zoonotic agents. For this reason, there is an emerging interest in domestic animals and wildlife as possible reservoirs for this parasite.
There have been many published studies of Giardia duodenalis in domestic dogs but relatively few for wild canids, reflecting the paucity of parasitological studies in wildlife
(Applebee et al., 2005; Thompson et al., 2010).
Domestic dogs are often infected with G. duodenalis assemblages C and D, but assemblages A and B are also common (van Keulen et al., 2002; Traub et al., 2004a;
Ipankaew et al., 2007; Leonhard et al., 2007; Covacin et al., 2010). Studies of wildlife species have also observed infections with assemblages A and B and these have raised questions on the transmission dynamics of this parasite (Graczyk et al., 2002; Fayer et al.,
2006; Thompson et al., 2009). Zoonotic transfer has been suggested between dogs and humans living in close conditions (Traub et al., 2004a; Lalle et al., 2005; Ipankaew et al.,
2007; Pelayo et al., 2008; Winkorth et al., 2008). However, the total risk appears to be low
(Hopkins et al., 1997; Berrilli et al., 2004). Alternatively, anthropozoonotic transfer has been suggested, whereby humans may infect other animals, particularly wildlife (Graczyk et al., 2002; Applebee et al., 2005; Caccio et al., 2005). Overall the transmission dynamics and subsequent risks to human health or wildlife are not well understood (Caccio et al.,
2005).
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The aim of this study was to examine wild and captive populations of the African painted dog for the presence of Giardia species, and to genetically characterise any isolates obtained from these populations using three loci, 18S rRNA, β-giardin and the glutamate dehydrogenase gene. This will enable identification of Giardia duodenalis at the assemblage and sub-assemblage levels and subsequently any health risk this parasite may pose within wild and captive environments of this endangered carnivore.
4.2 Materials and methods
4.2.1 Sample collection
Faecal samples were collected whilst tracking wild populations in Zambia and Namibia during three field trips conducted in 2007, 2008 and 2009. In most cases these samples were collected within moments of being deposited. The captive samples came from a population in a zoo in Australia (n = 17) which was also sampled in 2007, 2008 and 2009.
Additionally, two human faecal samples were obtained from zoo keepers working with the captive population, which had been approved by Murdoch University’s Human Research
Ethics Committee. All samples were given a consistency score of 1 to 5 with 1 being firm and 5 being liquid. See Chapter 2 for a full description of sample collection methods.
4.2.2 Parasitological techniques
Refer to Chapter 2 for a full description of microscopy methods used. All parasite ova and cysts observed were recorded, although only data for Giardia are reported here. All samples were then analysed using PCR protocols specific for Giardia, as described below.
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See Table 4.1 for samples which tested positive for Giardia through microscopy and/or with PCR amplification.
4.2.3 DNA extraction
A 2 ml aliquot of each ethanol-preserved sample was centrifuged and ethanol eluted. The remaining solid matter was used for DNA extraction using the Maxwell® 16 Instrument
(Promega, Madison, USA) as per manufacturer’s instruction. In an attempt to reduce the impact of inhibitors in carnivore faecal matter, the final elution was diluted to a 5:1 ratio with nuclease free water.
4.2.4 Amplification of 18S rRNA locus
A nested PCR was used for amplification of a 130 bp product of the 18S rRNA locus. The primary reaction utilized the primers RH11 and RH4 (Hopkins et al., 1997) and in the nested reaction primers GiarF and GiarR (Read et al., 2004) were used. The PCR reaction was performed in 25 μl volumes consisting of 1 µl of extracted DNA, 2.0 mM MgCl2, 1 x reaction buffer (20 mM Tris-HCL, pH 8.5 at 25 C, 50 mM KCl), 200 µM of each dNTP,
10 ρmol of each primer, 0.5 units of TAQ-Ti DNA polymerase (Fisher Biotec, Perth
Australia), and H2O. DMSO 5% was added to the primary round and 0.5 µl BSA (10 mg/mL) was added to the nested round. Amplification conditions were modified from
Hopkins (1997) and are as follows: the primary reaction was initiated with a denaturing step of 96 °C for 5 min, then 35 cycles of 96 °C for 45 s, 58 °C for 30 s and 72 °C for 45 s,
76 Chapter 4 – Molecular epidemiology of….. followed by a final extension of 72 °C for 7 min. The nested reaction was altered by a decrease in annealing temperature to 55 °C.
The PCR product was purified using a Wizard SV gel and PCR Clean-up system
(Promega, Madison, USA) after the manufacturer’s instructions, except the final elution was reduced to 20 µl from 50 µl. Sequence reactions were performed using the Big Dye
Terminator Version 3.1 cycle sequencing kit (Applied Biosystems) according to the manufacturer’s instructions. PCR products were sequenced in the reverse direction only
(GiarR), as initial sequencing of forward reactions was unsuccessful in this study as also seen in others (Leonard et al., 2007, Palmer et al., 2008). Reactions were electrophoresed on an ABI 3730 48 capillary machine. Assemblages were identified via single nucleotide polymorphisms (SNP’s) within the 130 bp sequence as previously described by Hopkins et al. (1997).
4.2.5 Amplification of β-giardin locus
A nested PCR was used for amplification of a 492 bp product of the β-giardin gene. The primary reaction utilized the primers G7 and G759 (Caccio et al., 2002) and in the nested reaction primers as described by Lalle (2005) were used. The PCR reaction was performed in 25 μl volumes consisting of 1 µl of extracted DNA, 2.0 mM MgCl2, 1 x reaction buffer
(67 mM Tris-HCl, 16.6 mM (NH4)2SO4, 0.45% Triton X-100, 0.2 mg/ml gelatin), 200 µM of each dNTP, 10 ρmol of each primer, 0.5 units of Tth Plus DNA polymerase (Fisher
Biotec, Perth Australia), and H2O. The primary reaction was initiated with a denaturing step of 95 °C for 5 min, then 40 cycles of 95 °C for 30 s, 65 °C for 30 s and 72 °C for 60 s,
77 Chapter 4 – Molecular epidemiology of….. followed by a final extension of 72 °C for 7 min. The nested reaction was altered by a decrease in annealing temperature to 55 °C and 35 cycles. The PCR product was purified and sequenced as described above for the 18S rRNA locus. Assemblages were identified via SNP’s within the 292 bp sequence when compared with reference sequences
AY072723, AY072727, AY072726, AY072725 and AY45646 (Caccio et al., 2002, Lalle,
2005).
4.2.6 Amplification of the glutamate dehydrogenase locus
A semi-nested PCR was used for amplification of a 432 bp product of the glutamate dehydrogenase (gdh) gene. The primary reaction utilized the primers GDHeF and GDHiR with GDHeR and GDHiR in the semi-nested reaction as described by Read et al. (2004).
The PCR reaction was performed in 25 μl volumes consisting of 1 µl of extracted DNA,
3.0 mM MgCl2, 1 x reaction buffer (67 mM Tris-HCl, 16.6 mM (NH4)2SO4, 0.45% Triton
X-100, 0.2 mg/ml gelatin), 200 µM of each dNTP, 10 ρmol of each primer, 0.5 units of Tth
Plus DNA polymerase (Fisher Biotec, Perth Australia), and H2O. DMSO 5% was added to the primary reaction only. Cycling conditions for both reactions were denatured at 94 °C for 5 min, then 45 cycles of 94 °C for 30 s, 60 °C for 30 s and 72 °C for 1 min, followed by a final extension of 72 °C for 4 min. The PCR product was purified, sequenced and analysed as previously described for the 18S rRNA locus. Assemblages were identified via
SNP’s within the 432 bp sequence when compared with reference sequences AY178735,
AY178737, AF069059, AY178739, L40508 and AY178738 (Monis et al., 1995; Monis et al., 1999).
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4.2.7 Data analysis
Of the 17 samples found positive with microscopy 12 were amplified with PCR along with
27 found negative with microscopy. Prevalence of infection was expressed as percentage of positive samples found either by microscopy or PCR, with 95% confidence intervals calculated assuming a binomial distribution, using the software Quantitative Parasitology
3.0 (Rozsa et al., 2000). Faecal consistency scores were compared between dogs testing positive or negative using a Wilcoxon rank sum test. Differences in prevalence between populations were tested using the Fisher’s exact test. To compare prevalences between wild and captive populations, data from year one (2007) of the captive population was tested against the total individual animals sampled from the wild. Sampling of the captive population was duplicated each year, but within wild populations animals were sampled only once as it was found that the composition of packs altered significantly from season to season, with many deaths recorded and therefore duplicate sampling was extremely rare.
Differences in prevalence of infection among years in the captive population were tested by a Cochran 2 test, with individual dogs as the blocking factor.
Genotypic information was obtained using the 18S rRNA locus. The multicopy nature and strong sequence conservation of 18S rRNA provide the sensitivity and specificity required to determine basic assemblage information (Weilinga and Thompson, 2007). However, to obtain sub-assemblage information the loci β-giardin and gdh loci were used, as has been done in many other studies (Abe et al., 2003; Read et al., 2004; Traub et al., 2004a; Lalle et al., 2005; Leonhard et al., 2007; Palmer et al., 2008). Resultant nucleotide sequences were compared with published sequences on NCBI. Sequences were aligned against reference sequences for β-giardin and gdh loci using the sequence alignment program
79 Chapter 4 – Molecular epidemiology of…..
Sequencher™ 4.8 (Gene Codes Corporation, Ann Arbor, USA), allowing assemblage and sub-assemblage assignment.
4.3. Results
4.3.1 Prevalence of infection
Table 4.1 shows the prevalence of infection with Giardia spp. within the two wild populations and one captive population of painted dogs. Prevalence of infection with
Giardia did not differ significantly between the two wild populations (P=1.00), but was significantly greater in the captive population than in either wild population (P=0.03 for comparison of captive and Zambian populations; P=0.02 for comparison of captive and
Namibian populations). Over all populations, there was no significant difference in faecal consistency scores between infected (mean score = 2.4 ± SE 0.19) and uninfected (2.3 ±
0.13) dogs (P = 0.78), with only three (n=87) samples presenting with diarrhoea (i.e. consistency score of 4 or 5).
Table 4.1 Prevalence of Giardia duodenalis (with 95% confidence intervals in parentheses) detected in faecal samples from captive and wild populations of the African painted dog.
Captive Wild - Zambia Wild - Namibia Wild-Total Cap vs Wild
(n=16) (n=43) (n=28) (n=71) P value
62% 28% 25% 27%
(37-82%) (16-43%) (12-44%) (17-38%) 0.009
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4.3.2 Molecular characterization of Giardia duodenalis isolates
All samples were initially screened at the 18S rRNA locus and identified as Giardia duodenalis. Samples successfully amplified at the 18S locus and/or found to be positive with microscopy were also amplified at the β-giardin and gdh loci. Within the captive population, isolates from 16 individual animals were successfully amplified at one, two or three loci. Amplification was successful for isolates from 14 animals at the 18S rRNA locus, three at β-giardin and six at gdh. Within the wild population, isolates from 14 individual animals were amplified: 13 at 18S rDNA, seven at β-giardin and one at gdh
(Table 4.2). Isolates from both captive and wild populations displayed variation in assemblage and sub-assemblage type depending on the locus used (Table 4.2).
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Table 4.2 Genotypic characterisation of Giardia duodenalis isolates from individual
African painted dogs at the18S rRNA, β -giardin and gdh loci. * Wild animals over 2yrs of age were allocated as Adult (A).
Captive population (n=16) Wild population (n=14) ID No Sex Age 18S β-g gdh ID No Sex Age* 18S β-g gdh C1 M 1 A/B - - W1 F A A - - C2 M 1 A/B - - W2 M 1 B A C3 M 3 B - A2 W3 ? ? B BIII - C4 M 1 B BIII/BIV - W4 F A B - - C5 M 2 B - BIV W5 M A A/B A2 - C6 M 2 B - - W6 F A A/D A2 - C7 M 2 A/B - - W7 M A B A2 - C8 M 3 B/C - - W8 M A A/B/C - - C9 M 7 B - - W9 ? A B - - C10 M 9 B - - W10 ? ? A/B - - C11 M 3 - - BIV W11 ? ? A/B - - C12 F 2 - BIII/BIV BIV W12 ? A - A2 - C13 F 1 B - - W13 M A C/D - - C14 F 4 B BIII/BIV A2 W14 F A A/B/C BIII BIV C15 F 4 B - D C16 F 8 B - -
Assemblage information obtained from the 18S rRNA gene showed a dominant proportion of samples in the captive population to be assemblage B (86%) with mixed assemblages
A/B and B/C/D both being 7%. Within the wild population assemblage B was also dominant with 38% of isolates however, greater variability was seen in the remaining isolates with several mixed assemblages.
82 Chapter 4 – Molecular epidemiology of…..
Longitudinal data were obtained from the captive population as sampling was conducted every year for three years (Table 4.3). Giardia duodenalis was observed in each year, with prevalences ranging between 50% and 69%. All animals tested positive at least once throughout the sampling period and there was no significant difference in prevalence among years (2 = 0.19, P = 0.16). Assemblages A and B were seen in high proportions in each year.
Table 4.3 Prevalence (with 95% confidence intervals in parentheses) and genotypic characterisation of Giardia isolates obtained in a captive population of African painted dogs over a three year period.
Sample year Prevalence 18S rRNA β-giardin gdh 2007 62% B=5 BIII/BIV=1 BIV=1 n=16 (37-82%) A/B=3
2008 50% B=5 BIII=1 n=14 (24-76%) B/C/D=1 BIII/BIV=1
2009 69% B=6 BIV=1 AII=2 n=13 (41-88%) BIII=1 BIV=1 A/B/D=1
Isolates obtained from the two zookeepers were also amplified at the 18S rDNA and β- giardin loci. Sequencing of the 18S rRNA gene revealed assemblage B and BIII/BIV at the
β-giardin locus for both isolates.
83 Chapter 4 – Molecular epidemiology of…..
4.4. Discussion
This study is the first to identify Giardia duodenalis in the African painted dog. Previous parasitological studies on this animal have not found this protozoan (van Heerden, 1986;
Colly and Nesbit, 1992; Peirce et al., 1995; van Heerden et al., 1995; Penzhorn, 2006).
The prevalence of G. duodenalis in the wild, 28% in the Zambian population and 25% in the Namibian population, was similar to other reports in wild canids, e.g. 12.5-32% in coyotes (Gompper and Williams, 1998; Trout et al., 2006; Thompson et al., 2009), and
46% in wolves (Klock et al., 2005). The greater prevalence found in this study in the captive population (62.5%) is most likely indicative of their captive environment. Animals are housed over long periods in the same area, allowing environmental build up and continued cycling of this protozoan within the population. This effect is reduced in wild populations as they are extremely nomadic.
This study was not successful in amplifying all isolates at all loci. Previous studies have also reported lower than expected amplification of Giardia DNA in dogs (Read et al.,
2004; Traub et al., 2004a; Robertson et al., 2006; Leonhard et al., 2007; Caccio and Ryan,
2008; Palmer et al., 2008). The inability to amplify at all loci may be attributed to several factors. First, β-giardin and gdh loci require high cyst numbers for amplification success
(Castro-Hermida et al., 2007). In addition, faecal samples from carnivores in general have low PCR success, due to the presence of inhibitors (Kohn and Wayne, 1997; Piggott and
Taylor, 2003; Covacin et al., 2010). Finally, the majority of samples in this study were not fresh but placed in a fixative, which was necessary to preserve DNA and to comply with quarantine restrictions for sample importation, but probably reduced the success of DNA
84 Chapter 4 – Molecular epidemiology of….. amplification due to degradation. Even when amplification was successful, some isolates showed differences in assemblage and sub-assemblage typing depending on the locus used.
This has also been found in previous studies and may be due to meiotic recombination or preferential amplification of one assemblage over another in mixed infections (Caccio et al., 2005; Cooper et al., 2007; Teodorovic et al., 2007; Caccio and Ryan, 2008).
Despite the difficulties mentioned above, it was possible to obtain some assemblage and sub-assemblage information for both wild and captive populations of the African painted dog. Genotypic information did not reveal any novel genotypes, but the zoonotic assemblages B and to a lesser degree A were prevalent within both populations. The dominance of these zoonotic assemblages was surprising especially as the dog assemblages
C and D were rarely seen. Assemblages A and B have been reported in studies on domestic dogs, coyotes and wolves but the dog assemblages have also been reported at similar prevalences (Table 4.4). The lack of assemblages C and D seen in both wild and captive populations of this study perhaps indicate that the African painted dog is not as susceptible for this genotype as members of the genus Canis. Interestingly, assemblage A has been the dominant zoonotic genotype reported in the literature in studies of both wild canids and domestic dogs, as opposed to this study, where assemblage B was the dominant genotype
(Table 4.4).
85 Chapter 4 – Molecular epidemiology of…..
Table 4.4 Assemblages of Giardia duodenalis observed in both wild canids and domestic dogs noted in the literature and this study. Number of times reported in literature is presented as (r=).
Host Assemblage Reference
Canis A (r=11) (van Keulen et al., 2002; Berrilli et al., 2004; Read et al., 2004; Traub et al., familiaris B (r=3) 2004a; Itagaki et al., 2005; Lalle et al., 2005; Ipankaew et al., 2007; Leonhard et al., 2007; Palmer et al., 2008; Covacin et al., 2010; Marangi et al., 2010)
C/ D (r=11) (Monis et al., 1998; Berrilli et al., 2004; Itagaki et al., 2005; Lalle et al., 2005;
Ipankaew et al., 2007; Leonhard et al., 2007; Souza et al., 2007; Palmer et al.,
2008)
Canis latrans A (r=3) (Gompper et al., 2003; Klock et al., 2005; Trout et al., 2006; Thompson et al., and B (r=1) 2009)
Canis lupus C /D (r=3)
Lycaon pictus A Present study
B
As noted in other wildlife studies, the presence of the zoonotic assemblages found in the
African painted dog raises the question of their potential to act as reservoirs for human infection (Graczyk et al., 2002; Trout et al., 2006; Thompson et al., 2009). The answer can perhaps be explained by their ecology and environment. Close interaction between dogs and humans living in rural communities in India has shown evidence of zoonotic transmission of Giardia (Traub et al., 2004a) and indeed this kind of transmission could well be possible within captive populations of the African painted dogs. The zoo keepers in our study had direct contact with the African painted dogs’ confined environment and were at risk of exposure through regular cleaning of water features and removing excrement
86 Chapter 4 – Molecular epidemiology of….. from the enclosure. Isolates from the two keepers typed to the same sub-assemblage as one of the captive animals in their care, suggesting that zoonotic transmission may have occurred. Evidence for zoonotic transmission within the zoo environment has also been observed for another protozoan, Blastocystis sp. whereby keepers and animals were found to harbour the same genetic sub-type of this parasite (Parkar et al., 2010).
In the wild, however, human contact with the African painted dog would be minimal. They are not companion animals and have never been domesticated. Due to their nomadic nature they will roam outside national parks and move through human settlements, although they actively avoid human contact, making zoonotic transfer unlikely (Creel and Creel, 2002).
However, there is a constant stream of tourists and locals into the national parks and as suggested by Graczyk et al. (2002) studying gorillas in Uganda, indiscriminate defecation by humans could be a source of Giardia infection. Other evidence for anthropozoonotic transmission has been seen between humans and beavers, where humans have been implicated in introducing Giardia to beavers through sewage runoff upstream from the beaver colony (Bemrick and Erlandsen, 1988; Fayer et al., 2006).
Whilst the transmission of Giardia duodenalis from humans to African painted dogs remains speculative, it appears that once established within these packs infection is maintained by dog to dog transmission. They are very social animals and physical contact is common in all aspects of pack life, providing ample opportunity for transmission to occur (Woodroffe et al., 1997; Creel and Creel, 2002). This was evident in the captive population as each individual animal displayed an infection with G. duodenalis at some point over the three year study period. As previously mentioned, prevalence was far lower
87 Chapter 4 – Molecular epidemiology of….. in the wild populations and distribution among packs was not even. G. duodenalis was observed in several individuals in the same pack and in none in other packs, again suggesting that once the parasite is introduced into a pack, animal to animal transmission occurs.
The pathogenesis of Giardia spp. to the host is complicated as many infected hosts can be asymptomatic while others display severe diarrhoea (Eckmann, 2003). In this study, only three of the 85 faecal samples positive for G. duodenalis showed signs of diarrhoea, suggesting that parasitic infection in these animals was generally asymptomatic. Perhaps of more importance than clinical symptoms are the potential subclinical effects. Infections with Giardia spp. have been related to growth retardation and malabsorption in children, particularly those with poor nutrition (Astiazaran-Garcia et al., 2000; Berkman et al.,
2002). With respect to African painted dogs, which often have concurrent enteric infections (see Chapter 3), subclinical impacts of G. duodenalis could be of great importance, particularly as pack sizes decrease and hunting efficacy declines (Creel and
Creel, 1995; Courchamp et al., 2002).
Ultimately, the transmission dynamics of G. duodenalis within the African painted dog remains unclear. While this species could act as a reservoir for zoonotic infections, the lack of direct human contact in the wild make this unlikely. However, increased human activity into their natural environment clearly has the potential to increase the prevalence of G. duodenalis infections in the African painted dog. With other pressures this could potentially be an emerging disease, which will require monitoring in the future. This dynamic, however, is altered within captive populations. Due to the necessary interaction
88 Chapter 4 – Molecular epidemiology of….. between humans and their captive charges in this environment, the risk of zoonotic transfer is high and should be a consideration in future management protocols.
4.4.1 Conclusions
In summary, the prevalence of G. duodenalis observed in this study indicates that this parasite is an important part of the parasite fauna of both wild and captive populations of the African painted dog. Molecular techniques have demonstrated that both wild and captive populations are predominantly infected with the zoonotic assemblages of G. duodenalis, and therefore pose a potential zoonotic risk for zoo keepers and surrounding communities in the natural environment. The subclinical effects of infection are unknown, but are potentially detrimental to small packs with limited prey capture success and subsequent poor nutrition. This is the first report of G. duodenalis within the painted dog and may indicate an emerging disease with possible zoonotic/anthropozoonotic transmission modes. This highlights the need for continued research to be conducted on wildlife and their surrounding influences to ascertain more precisely the nature of any threats to the charismatic but endangered African painted dog.
89 Chapter 5 – Hookworm species of…..
Chapter 5
Hookworm species of the African painted dog and the significance of infection
90 Chapter 5 – Hookworm species of…..
5.1 Introduction
The family Ancylostomatidae contains parasitic nematodes which infect the small
intestine of a wide range of mammalian hosts. These nematodes have a large buccal
cavity, usually armed with teeth, at the anterior end which assists in attachment to the
hosts’ intestinal wall. The anterior end is often ‘hooked’ in appearance, giving rise to
the nomenclature of Ancylostoma with ancyl being Greek for ‘hook’ and stoma for
‘mouth’ (Dubini, 1843).
Infection of the host can occur either through direct ingestion or skin penetration of
infective larvae (L3) (Looss, 1898; Fulleborn, 1914) (Figure 5.1). Larvae which
penetrate the skin usually undergo a tracheal migration where larvae migrate to the
lungs, are ‘coughed’ into the trachea, swallowed and taken through the digestive system
where eventually they reach the small intestine to then attach, feed and reproduce
(Looss, 1898; Bowman et al., 2003). Alternatively L3 may undergo somatic migration
whereby larvae move through the host tissue and localize in the skeletal muscle and
enter into a hypobiotic (dormant) state. These dormant larvae are able to reactivate, move into the gut and develop into reproducing adults when optimal transmission conditions occur (Loukas and Provic, 2001). An example of this is when a canid host gives birth. Encysted larvae are reactivated towards the end of the pregnancy and are ready to produce large quantities of eggs for quick transmission to the newly born pups
(Bowman et al., 2003). Pups can also be infected through transmammary transmission, which occurs when larvae emerging from hypobiosis migrate to the mammary glands and pass through to nursing pups in the dam’s milk (Figure 5.1). Both routes of infection result in large parasite loads within these young hosts often leading to severe anaemia as a direct result of the feeding activities of these parasites (Kalkofen, 1970).
Canid hookworm species are important concerns for both animal and human health as
91 Chapter 5 – Hookworm species of….. besides the ability to cause clinical disease in canids, these hookworms also have the potential to infect humans.
Figure 5.1 Depiction of the lifecycle of Ancylostoma caninum in domestic dogs adapted from www.Apaws.org.
.
5.1.1 Hookworm in the canid host
The most widespread species of hookworm infecting canids is Ancylostoma caninum which has a cosmopolitan distribution (Miller, 1971). Other hookworm species commonly infecting canids include A. braziliense, A. ceylanicum and Uncinaria stenocephala all of which have a more restricted distribution. U. stenocephala is commonly observed in the cooler climates of Europe, North America and Australia, while A. braziliense and A. ceylanicum are observed in warmer tropical and sub- tropical regions (Levine, 1968; Provic, 1998; Beveridge, 2002). A. braziliense is quite widely distributed in these regions but to date A. ceylanicum has only been reported in
92 Chapter 5 – Hookworm species of…..
Southeast Asia, India and more recently Australia (Yoshida et al., 1973; Choo et al.,
2000; Loukas and Provic, 2001; Traub et al., 2004b; Palmer et al., 2007).
Within the canid host, hookworm infections can range from being largely
asymptomatic to severely pathogenic depending on the species of hookworm,
magnitude of infection and the susceptibility of the host (Bowman et al., 2003). A.
caninum infections are often more pathogenic to the canid host due to a greater rate of
blood loss than seen with A. ceylanicum, A. braziliense or U. stenocephala infections
(Miller, 1966; Areekul et al., 1975; Bowman et al., 2003). However, heavy infections
of most hookworm species can lead to clinical disease (Carroll and Grove, 1984). The
magnitude of infection depends on the level of exposure to infective larvae in the
environment, which in turn is dependent on proximity of other infected hosts and
suitability of the environment for the development and survival of the L3.
Host susceptibility is often dependent on age and immune function with young animals and older immunocompromised animals most at risk, with even light infections capable
of causing illness and death. However, hosts with prior exposure or premunition are
often asymptomatic. Carroll and Grove (1985) demonstrated this ability for acquired
resistance to A. ceylanicum in experimental trials on dogs. They found that dogs
currently infected with small numbers of hookworms were considerably resistant to a
challenge infection of a large inoculum of infective larvae, while dogs previously
uninfected with hookworm developed marked anaemia when inoculated.
5.1.2 The zoonotic potential of canid hookworm species
Canid hookworm species have zoonotic potential and are associated with a variety of
diseases in humans (Carroll and Grove, 1986; Chaudhry and Longworth, 1989; Croese
93 Chapter 5 – Hookworm species of…..
et al., 1994). All canid hookworm species are capable of causing cutaneous larval
migrans (CLM), also known as ‘creeping eruptions’ (Kirby-Smith, 1926; Carroll and
Grove, 1986; Jelinek et al., 1994). CLM is a pruritic skin disease which is the result of
infective hookworm larvae penetrating and migrating through the skin (Jelinek et al.,
1994). Cases of CLM are most often described in hot climates including SE Asia,
Africa and Latin America with A. braziliense the most common etiological agent
involved (Chaudhry and Longworth, 1989). A. caninum has been shown to sometimes
migrate further than the skin reaching the human gut where it can cause eosinophilic
enteritis; however evidence of patency has not yet been observed (Croese et al., 1994).
A. ceylanicum is the only hookworm of dogs that is capable of producing patent
infections in the human host, with patients experiencing intermittent abdominal
discomfort throughout the period of infection (Carroll and Grove, 1986).
5.1.3 Hookworm in the African painted dog and other carnivores in Africa
Reports of hookworm within African animals have mainly been from domestic dogs
and cats with A. caninum most common in dogs and A. tubaeforme in cats (Baker et al.,
1989; Minnaar and Krecek, 2001; Minnaar et al., 2002). A. braziliense was also
reported in these studies but at slightly lower prevalences. Baker et al. (1989) reported parasitological studies during autopsies on 1,500 stray cats and identified A. ceylanicum at a prevalence of 1.4%. To date this is the only report of this Ancylostoma species in
Africa in either human or animal populations. Reports of hookworm species in native
African carnivores are less common, however A. caninum and A. braziliense have been identified in cheetah (Acinonyx jubatus), leopard (Panthera pardus) and jackal (Canis spp.) (Round, 1968). A. ceylanicum was also reported in an African civet (Viverra
civetta), although during this time A. ceylanicum and A. braziliense were considered
94 Chapter 5 – Hookworm species of….. synonymous and were not officially differentiated until 1951 (Bioca, 1951; Round,
1968). With this redescription it has been suggested that many old records are in doubt, therefore this identification is also questionable (Dunn, 1969). The only reports of hookworm in the African painted dog have been from van Heerden et al. (1994, 1996) who found A. caninum in a captive and wild population in South Africa.
5.1.4 Diagnosing hookworm infections
In the past, studies using microscopy to identify parasite ova have had to presume or suggest which species of Ancylostoma was the infecting agent based on previous observations from that host and the known distribution of hookworm species (Engh et al., 2003; Smith and Kok, 2006). This may have led to erroneous reports as the identification of Ancylostoma species from parasite ova alone is not possible.
Traditional methods of species identification have involved obtaining adult worms, usually during necropsy, which in turn required considerable expertise to differentiate.
Historically, misidentifications have been made, particularly between A. ceylanicum and A. braziliense due to the morphological similarities between the two, creating doubt on known distributions (Dunn 1969). Recent development of molecular tools to differentiate hookworm species from faecal samples has been able to alleviate these diagnostic problems and allow for more accurate species identification and subsequently more accurate distribution records for parasites (Palmer et al., 2007;
Traub et al., 2008). For example, the distribution of A. ceylanicum was only recently found to include Australia (Palmer et al., 2007). This range extension was demonstrated with the use of molecular tools which were able to differentiate between eggs from different Ancylostoma species from canine faeces (Traub et al., 2004b).
95 Chapter 5 – Hookworm species of…..
The primary aim of this study was firstly, to establish the prevalence of Ancylostoma spp. in captive and wild populations of the African pained dog and secondly, to identify if species of pathogenic and/or zoonotic importance occur within these populations.
These aims were achieved by obtaining data from three wild and three captive populations for comparative analysis. Molecular characterisation was conducted to identify species of Ancylostoma.
5.2 Materials and methods
5.2.1 Sample collection
Faecal samples were collected whilst tracking wild populations in Zambia and Namibia during three field trips conducted between 2007 and 2009. The population within
Zambia was sampled in each of the three years while the population in Namibia was sampled in two of these years (2008 and 2009). Samples in Zimbabwe had been collected in 2006 and stored for later analysis. The samples from captive animals were collected from two zoo populations in Australia (Perth Zoo, Monarto Zoo) and a rehabilitation facility in South Africa. See Chapter 2 for a full description of sample collection methods.
5.2.2 Parasitological techniques
Refer to Chapter 2 for a detailed description of microscopy techniques. All parasite ova and cysts observed were recorded, although only data for Ancylostoma spp. are reported here. All samples were then analysed using PCR protocols specific for Ancylostoma spp., as described below.
96 Chapter 5 – Hookworm species of…..
5.2.3 DNA extraction
A 2 ml aliquot of each ethanol-preserved sample was centrifuged and ethanol eluted.
The remaining solid matter was used for DNA extraction using the Maxwell® 16
Instrument (Promega, Madison, USA) as per the manufacturer’s instruction. In an
attempt to reduce the impact of inhibitors in carnivore faecal matter, the final elution
was diluted to a 5:1 ratio with nuclease free water.
5.2.4 Amplification of Ancylostoma spp. isolates at the ITS1 and ITS2 regions
Modifications from Traub et al. (2008) were used for amplification of a 380 bp product
of the ITS1, 58S and ITS2 regions using primers RTHW1F and RTHW1R. The PCR
reaction was performed in 25 μl volumes consisting of 1 µl of extracted DNA, 2.5 mM
MgCl2, 1 x reaction buffer (20 mM Tris-HCl, pH 8.5 at 25 °C, 50 mM KCl), 100 µM of
each dNTP, 10 ρmol of each primer, 0.5 units of Tth plus DNA polymerase (Fisher
Biotec, Perth Australia), and H2O. Amplification conditions were as follows: the primary reaction was initiated with a denaturing step of 95 °C for 5 min, then 40 cycles
of 95 °C for 30 s, 60 °C for 30 s and 72 °C for 30 s, followed by a final extension of 72
°C for 7 min. The PCR product was purified using an Agencourt AMPure XP system
(Beckman Coulter Inc, Brea USA) according to the manufacturer’s instruction.
Sequence reactions were performed using the Big Dye Terminator Version 3.1 cycle
sequencing kit (Applied Biosystems), according to the manufacturer’s instructions.
PCR products were sequenced in both directions. Reactions were electrophoresed on an
ABI 3730 48 capillary machine.
97 Chapter 5 – Hookworm species of…..
5.2.5 Data analysis
Prevalences of infection were expressed as a percentage of positive samples found by
microscopy with 95% confidence intervals calculated assuming a binomial distribution,
using the software Quantitative Parasitology 3.0 (Rozsa et al., 2000). Differences in
prevalence between populations and years were tested using the Fisher’s exact test or
chi-square test. Resultant nucleotide sequences were compared with published
sequences on NCBI GenBank using the basic alignment search tool (BLAST). Further
sequence analysis was conducted using the sequence alignment program Sequencher™
4.8 (Gene Codes Corporation, Ann Arbor, USA). Reference sequences for A. caninum,
A. duodenale and A. braziliense (accession numbers A. caninum DQ438079 and
EU159416, A. duodenale EU344797 and AB501351, A. braziliense DQ438054) were used in the alignments. The levels of sequence differences (D), based on pairwise comparisons, were calculated using the formula D = 1 – (M/L), where M is the number of alignment positions at which the two sequences have a base in common and L is the
total number of positions over which the sequences are compared (Chilton et al., 1997).
The level of sequence difference was expressed as a percentage.
5.3 Results
5.3.1 Prevalence of infection
Table 5.1 shows the prevalence of infection with Ancylostoma spp. within captive and
wild populations. Prevalence of infections did not differ significantly between the three
wild populations (Fisher’s exact tests, Zambia vs. Namibia P=0.4; Zambia vs.
Zimbabwe P=0.14; Namibia vs. Zimbabwe P=0.6). There was a significant difference in prevalence between wild and captive populations, as Ancylostoma spp. were not
observed in any of the captive populations sampled (Fisher’s exact test, P< 0.0001).
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Table 5.1 Prevalence of Ancylostoma spp. (with 95% confidence intervals in parentheses) detected in faecal samples from captive and wild populations of the
African painted dog.
Zimbabwe Zambia Namibia Total wild Total captive
(n=12) (n=43) (n=28) (n=83) (n=130)
8 % 32.6% 43% 32.5% 0
(0.4 – 37%) (19 – 48%) (26 – 62%) (23 – 43%)
Data was obtained over three years for the Zambian population and two years for the
Namibian populations. Ancylostoma spp. were observed in each year with prevalences ranging from 20% to 66.7% (Table 5.2). There were significant differences in prevalences among years within the Zambian population (χ2 = 6.306, P=0.04) but not between years in the Namibian population (Fisher’s exact test, P=1.000).
Table 5.2 Prevalence of Ancylostoma spp. observed in the Zambian and Namibian populations of the African painted dog over a three year period. Sample size (n) and
95% confidence intervals in parentheses.
Population Year
2007 2008 2009
Zambia 66.7% (n=9) 20% (n=20) 28.6% (n=14)
(32 – 90%) (71 – 42%) (10 – 57%)
Namibia 42% (n=19) 44% (n=9) -
(22 – 66%) (17 -75%)
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5.3.2 Molecular characterisation of Ancylostoma spp. isolates
Of the 27 samples identified positive for Ancylostoma spp. ova by microscopy, a subset were chosen for molecular characterisation. Four samples were successfully amplified at the ITS1 and ITS2 regions. A BLAST search on GenBank revealed three isolates from the Namibian population (N-B08, N-K17 and N-U12) to be Ancylostoma braziliense and one isolate from the Zambian population (Z-Ka01) was found to have a similar identity to both Ancylostoma caninum and Ancylostoma duodenale (Table 5.3).
Table 5.3 Genotypic characterisation of Ancylostoma spp. isolates obtained from wild populations of the African painted dog within Zambia and Namibia. Percentages shown for matched identities with published sequences in parentheses.
Population Isolate Host Sex Host Age Ancylostoma species
Namibia N-B08 ? ? A. braziliense (100)
Namibia N-K17 ? Adult A. braziliense (100)
Namibia N-U12 ? ? A. braziliense (100)
Zambia Z-Ka01 M Yearling A. caninum (99) A. duodenale
(99)
The isolate Z-Ka01 was aligned against reference sequences of A. caninum (accession numbers DQ438079 and EU159416) and A. duodenale (accession numbers
AB501351and EU344797). Over a 301 bp region there was one different nucleotide
100 Chapter 5 – Hookworm species of…..
difference with A. duodenale and two nucleotide differences with A. caninum (Table
5.4).
Table 5.4 Summary of the nucleotide variations detected between the painted dog isolate from Zambia (Z-Ka01) and reference sequences for A. caninum and A. duodenale. Alignment was conducted in Sequencher™ 4.8 and dots indicate identity with the first sequence.
Ancylostoma isolates Alignment position
324 353 355
A. caninum EU159416 T C C
A. caninum DQ438079 . T .
A. duodenale EU344797 A T T
A. duodenale AB501351 . T T
Z-Ka01 . T T
5.4 Discussion
Ancylostoma spp. were not detected within any of the captive populations of the
African painted dog. This was most likely due to the regular use of anthelmintics in the
captive facilities (see Chapter 2). In comparison, the total prevalence of Ancylostoma
spp. observed in the wild populations of painted dogs in this study was 32.5%. This was
slightly higher than previously reported by van Heerden et al. (1995), (22.4%) but
101 Chapter 5 – Hookworm species of…..
varies from studies on competitor species such as hyaena, which reported a prevalence
of 56%, and lion (90%) (Muller-Graf, 1995; Engh et al., 2003). It is not clear whether
the higher prevalences observed in studies of hyaena and lion were due to
environmental conditions or differences among hosts in exposure or resistance to
hookworm infection.
In this study prevalence of infection was not significantly different between African
painted dog populations in different geographic regions, however, within the Zambian population a significant difference was observed over time. This variation was mainly due to the higher prevalence observed in 2007, which also had the majority of samples collected in the wet season. The wet season in these regions provide a moist and warm environment which are optimal conditions for the transmission and survival of hookworm larvae and this is the most likely explanation for the observed increased prevalence in 2007.
The use of molecular tools in this study allowed for species identification of a small
subset of isolates. Using the ITS region of hookworm rDNA it was possible to
distinguish between the main species of canid hookworms (Traub et al., 2004b; Clare e
Silva et al., 2006). A major benefit of using molecular tools is that it avoids the need for
adult worms which are usually only obtained during a necropsy and require substantial
skill to confidently identify (Traub et al., 2004b). This is particularly important when
dealing with endangered wild animals, where the chances of obtaining carcasses for
necropsy is rarely possible. Faecal sampling provides a non-invasive method to obtain
parasitological data, from which molecular tools can then assist in providing species
information.
102 Chapter 5 – Hookworm species of…..
The ability to identify the species of hookworm infecting a host population is of particular significance as pathogenicity and zoonotic potential vary between the different species. For example, A. caninum poses a greater health risk to the host as it causes greater blood loss than the other species, whilst A. braziliense commonly causes
CLM in humans and A. ceylanicum can lead to patent infections in man (Miller, 1966;
Carroll and Grove, 1986). Additionally, as correct species identification has been
impossible through egg morphology, the exact geographic distribution for these
hookworm species is not completely mapped, making molecular characterisation an
important tool in achieving this.
Genetic characterisations conducted in this study identified three isolates from the
Namibian population of painted dogs to be A. braziliense. This is the first identification
of this species of hookworm in the painted dog and potentially represents a zoonotic
risk to the surrounding human communities. A previous study on communities situated
near this study population has implicated A. braziliense as a major cause of CLM
commonly seen in hospital patients (Evans et al., 1990). Theoretically, these animals
could be reservoirs for CLM in human communities but the lack of human contact in
the wild would reduce the chance of transmission (see Chapter 4).
A more likely explanation for the CLM seen in human populations would be zoonotic infection from the large number of domestic dogs living in close contact with these
communities. A. braziliense has been reported in domestic dogs in Africa with
prevalences ranging from 19% to 79% (Pangui and Kaboret, 1993; Minnaar and
Krecek, 2001; Minnaar et al., 2002). Two concurrent studies conducted in different
regions of South Africa found that the prevalence of A. caninum was significantly less
in the study site with the drier climate (27% vs. 88%) whilst A. braziliense had similar
103 Chapter 5 – Hookworm species of….. prevalences in both climates (19%, 20%). The authors therefore suggested that A. braziliense were more resistant to dry environment than A. caninum (Minnaar and
Krecek, 2001; Minnaar et al., 2002). Conclusive evidence for this is lacking in the literature but another study on domestic dogs in Dakar, Senegal, which has a semi-arid climate found A. braziliense at much higher prevalences than A. caninum (79% vs.
17%) (Pangui and Kaboret, 1993). A. braziliense was the only species identified from
Namibia in this study, which is a region that experiences a desert dry environment for most of the year and a shorter wet season than the other study sites of Zambia and
Zimbabwe.
The single isolate which was sequenced from the Zambian population could not be conclusively identified as either A. caninum or A. duodenale due to the lack of polymorphisms within the sequenced region. A. duodenale is known as a human hookworm but is also found in cats and dogs. This species has not been previously reported in the African painted dog although it has been reported in the spotted hyaena in Ethiopia (Graber and Blanc, 1979). A. caninum has been reported in both a captive and wild population of the African painted dog (van Heerden et al., 1994). However, it must be noted that the study on the wild population within Kruger National Park identified A. caninum from one adult worm obtained from one painted dog during necropsy. It appears that it was then assumed that all Ancylostoma spp. ova observed in faecal samples of that study were of the same species, which may well have been inaccurate. Studies have since identified A. braziliense within domestic dog populations of South Africa, providing evidence that the species exists within the region and is therefore a possible suspect (Minnaar and Krecek, 2001; Minnaar et al., 2002). As molecular tools become more widely used these issues may be resolved.
104 Chapter 5 – Hookworm species of…..
Pathogenicity of hookworm infection within wild populations of the African painted
dog is unknown (van Heerden et al., 1995). It is likely that some mortality events occur
but identifying these in the wild is hindered by the inability to find dead animals in
what is often inaccessible terrain, combined with the efficiency of scavengers in
cleaning up carcases. Nonetheless, the painted dogs are extremely social animals so the
transmission of hookworm between individuals would be greatly enhanced.
Transmission would be significantly increased during the denning period when
reactivated larvae in the dam increase ova output and pups and pack members are confined to the den and surrounding areas. It appears the prevalence of hookworm observed in these wild populations was sustainable as study animals appeared robust and healthy. This display of health may be the result of acquired immunity by the host or, as has been previously noted, wild animals tend to manifest few recognizable signs of disease (Sachs and Sachs, 1968; Young, 1969). This apparent health has been observed in other wild populations who are host to potentially pathogenic parasites.
Wild populations of zebra are known to harbour a variety of Cyathostomum spp., of which several species are pathogenic to domestic equines, but the zebra host appears to display no clinical effects (Roberts et al., 2002). Similarly, populations of wild ruminants within north America are host to many gastrointestinal strongyle parasites, many of which are pathogenic to domestic livestock, but again negligible clinical effects have been in observed in these wild hosts (Hoberg et al., 2001).
The ability for the canid host to acquire a level of immunity to hookworm infections is an important consideration for captive animal management, especially those involved in reintroduction programs. The prevalences observed in this study indicate that hookworm infections are common within wild populations while captive animals have no or minimal exposure. Therefore, facilities with animals marked for reintroduction
105 Chapter 5 – Hookworm species of….. programs may benefit from maintaining a low level of infection in order for animals to acquire a level of immunity against species such as hookworm. In addition, exposure to
A. caninum can lead to cross immunity for other hookworm species such as A. braziliense (Miller, 1967). These factors would then reduce the impact of the substantial parasite challenge animals will be faced with on release to the natural environment (Williams et al., 1992; Viggers et al., 1993).
There is a risk involved in maintaining infections with naturally occurring parasites in a captive environment as the confined conditions can lead to a rapid increase in parasite numbers. Therefore, adequate monitoring would be required to ensure infection levels remained low to avoid clinical disease, but the benefits may be worth the extra labour involved. It should be noted that ancylostomiasis has been implicated in the death of two captive painted dogs (van Heerden et al., 1994). However, one animal was a pup and the other was an immunocompromised adult, both of which were particularly susceptible to hookworm infections. Depending on individual facilities the risk of some mortality may be acceptable in view of the benefits potentially gained.
5.4.1 Conclusions
In summary, these prevalence data suggest that Ancylostoma species make up an important part of the parasite fauna of wild populations of the painted dog. Molecular techniques have been successful in identifying A. braziliense for the first time in this endangered carnivore and indicate a possible zoonotic risk for the surrounding human communities. As DNA from only a small subset of samples was successfully amplified and sequenced, limited information on geographic distribution was obtained. Future
106 Chapter 5 – Hookworm species of….. studies are required to achieve detailed species distribution within endangered carnivores such as the African painted dog.
107 Chapter 6 – Detecting Taenia species in…
Chapter 6
Detecting Taenia species of the African painted dog
108 Chapter 6 – Detecting Taenia species in…
6.1 Introduction
The cestode family Taeniidae consists of two genera, Taenia Linnaeus, 1758 and
Echinococcus Rudolphi 1801¸ both of which include species of medical and veterinary significance (Eckert et al., 2001; Hoberg, 2002). These taeniids have a two host lifecycle based around a carnivorous definitive host and an omnivorous or herbivorous intermediate host. The adult worm lives in the gut of the definitive host where it produces proglottids which once mature contain multiple ova. These proglottids and ova are passed out in the hosts’ faeces and are subsequently ingested by grazing herbivores and omnivores. Once ingested by the intermediate host the ova develop into a larval stage, or metacestode, which encysts within the tissues and internal organs of the intermediate host. These metacestodes are fluid-filled cystic structures which depending on the species develop into cysticerci, strobilocerci, coenuri or hydatid cysts (Bowman et al., 2003). Cysticerci and strobilocerci contain one scolex from which one mature tapeworm can develop. Coenuri contain multiple scolices and hydatid cysts can contain thousands of scolices (protoscolices). The latter two are usually associated with pathogenic disease in the intermediate host due to the invasive or space occupying nature of the cysts. The taeniid lifecycle is completed when these metacestodes are ingested by a carnivorous definitive host (Figure 6.1).
109 Chapter 6 – Detecting Taenia species in…
Definitive host
Intermediate hosts
Figure 6.1.The lifecycle of a taeniid species depicting the transmission cycle between predator (definitive host) and prey (intermediate host).
There are multiple species within both genera of taeniids and there has been much discussion and redescription in the literature in an attempt to discern the epidemiology of each species (Verster, 1969; Rausch, 1994; Hoberg et al., 2000; Thompson and McManus,
2002; Hoberg, 2006). Currently within the genus Taenia there are approximately 42 described species and 3 subspecies, while Echinococcus has a possible 9 species and several strains of E. granulosus (Loos-Frank, 2000; Thompson and McManus, 2002;
Huttner et al., 2008; Huttner and Romig, 2009). However, it should be noted that many
‘strains’ of E. granulosus have recently been awarded species status (Thompson and
McManus, 2002; Huttner et al., 2008). While complete lifecycles are not known for all species of taeniids it has been found that in general these parasites have relatively high definitive host specificity and relatively low intermediate host specificity (Verster, 1969).
There are some exceptions to this, such as E. granulosus and T. hydatigena being found in
110 Chapter 6 – Detecting Taenia species in… several different species of definitive hosts (Verster, 1965, 1969). Within African wildlife, top level carnivores such as lion (Panthera leo), hyaena (Crocuta crocuta, Hyaena brauni, and Hyaena hyaena), jackal (Canis mesomelas and C.adustus) and African painted dog
(Lycaon pictus) are commonly definitive hosts for taeniids (Dinnik and Sachs, 1969;
Verster, 1969; Jones and Khalil, 1984). The African lion has been found to be a definitive host for T. regis and T. simbae, hyaena species are definitive hosts for T. dinniki, T. hyaenae, T. crocutae and T. olngojinei and the silver-backed jackal is host to T. madoquae
(Pellegrini, 1950; Mettrick and Beverley-Burton, 1961; Dinnik and Sachs, 1972; Jones and
Khalil, 1984). The transmission cycles of these Taenia species invariably involves several wild ungulates, particularly antelopes, as the intermediate host. For example, species of antelope such as impala (Aepyceros melampus), gazelle (Gazella spp.), kudu (Tragelaphus spp.) and wildebeest (Connochaetes spp.) have been found to harbour the metacestodes of
T. crocutae, T. hyaenae, T. hydatigena, T. madoquae, T. olngojinei and T. simbae (Table
6.1) (Nelson and Rausch, 1963; Dinnik and Sachs, 1969; Verster, 1969; Dinnik and Sachs,
1972; Jones and Khalil, 1984).
Reports of taeniid species within the African painted dog have been few with the majority being made in the first half of the 20th century. These early observations included T. lycaontis, T. brauni and E. lycaontis (Ortlepp, 1934; Mahon, 1954; Baer and Fain, 1955) all of which were later revised and found to be synonymous with T. hyaenae, T. serialis brauni and E. granulosus respectively (Verster, 1969). Less disputable are observations
111 Chapter 6 – Detecting Taenia species in…
Table 6.1 Definitive and intermediate hosts of Taenia spp. infecting African carnivores.
Taenia species Distribution Definitive host Intermediate host Metacestode location
T. crocutae Africa Hyaena sp. Antelope: eg. impala, kudu and Cysticerci – skeletal muscle duiker
T. dinniki Africa Hyaena sp. Unknown Unknown
T. hyaenae Africa Hyaena sp. Antelope: eg. impala and sable Cysticerci – muscles, heart, tongue, diaphragm (syn T. lycaontis) African painted dog
T. hydatigena Cosmopolitan Dog and other canids Ruminants Cysticerci – pelvic regions, liver, lungs
T. multiceps Cosmopolitan Dog and other canids Sheep and goat Coenurus – CNS, brain
T. serialis Cosmopolitan Dog and other canids Lagomorphs Coenurus – intermuscular tissue, heart
T. s. brauni Africa Dog and other canids Rodents and primates Coenurus – intermuscular tissue heart
African painted dog
T. madoquae Africa Silver-backed jackal Antelope (Madoqua sp.) Cysticerci – skeletal muscle
T. ovis Cosmopolitan Dog and other canids Sheep and other ruminants Cysticerci – skeletal muscle, heart, diaphragm
T. olngojinei Africa Spotted hyaena Antelope eg. Grants gazelle Cysticerci – intrasacral muscle
T. regis Africa African lion Antelope Cysticerci – skeletal muscle, liver, lung
T. simbae Africa African lion Antelope Unknown
112 Chapter 6 – Detecting Taenia species in… of T. pisiformis and E. granulosus infections within the painted dog (Ortlepp, 1934, 1938;
Nelson and Rausch, 1963; Young, 1975). Besides these individual findings, one parasitological prevalence study has been conducted on painted dog packs within Kruger
National Park which identified the prevalence of taeniid species to be 30% (van Heerden et al., 1995).
There have been relatively few other prevalence studies of taeniids in African carnivores but two studies on lions observed a prevalence of 58% and 15% (Muller-Graf, 1995; Bjork et al., 2000) and one study on hyaena reported 12.9% (Engh et al., 2003). Due to data for these studies being obtained from faecal samples and the subsequent lack of adult worms, identification of species was not made.
The presence of taeniids within wildlife does not pose an immediate threat to the definitive host as most adult tapeworms do not invade or feed off host tissue and are therefore considered non-pathogenic (Bowman et al., 2003). However, there is a risk of zoonotic disease as humans can act as intermediate hosts for many of these taeniid species. Of the two genera, species of Echinococcus are considered more pathogenic as these parasites form large hydatid cysts in the organs of the intermediate host, resulting in hydatid disease in humans (Eckert et al., 2001). Among the species of Taenia, which utilize canids as the definitive host, are members that are also potentially pathogenic to people. Examples include T. multiceps, T. serialis and T. s. brauni which have been known to cause cerebral coenurosis and ocular coenurosis in humans (Vanderwick et al., 1964; Templeton, 1968;
Williams and Templeton, 1971; Ibechukwu and Onwukeme, 1991). Humans most at risk to possible zoonoses in wildlife are those in communities situated near or in national parks,
113 Chapter 6 – Detecting Taenia species in… where human/wildlife interactions are more common. Whilst cerebral and/or ocular coenurosis is relatively rare, hydatid disease has been found to be highly endemic in sub-
Saharan Africa with studies on nomadic pastoralists reporting a prevalence of between 0.1 and 5.6% (Macpherson et al., 1989; Magambo et al., 2006).
The aim of this study was to firstly determine the prevalence of taeniid species within wild and captive populations of the African painted dog, secondly to identify the species involved, which may assist in understanding sylvatic predator/prey transmission cycles and thirdly, to identify any species which may pose a public health risk. These aims were achieved by obtaining data from three wild and three captive populations for comparative analysis. Identification of species was achieved by staining proglottids and molecular characterisations, while the known predator/prey relationships within each study population were used to infer sylvatic lifecycles.
6.2 Materials and methods
6.2.1 Sample collection
Faecal samples were collected whilst tracking wild populations in Zambia and Namibia during three field trips conducted between 2007 and 2009. The population within Zambia was sampled in each of the three years while the population in Namibia was sampled in two of these years (2008 and 2009). Samples in Zimbabwe had been collected in 2006 and stored for later analysis. The samples from captive animals were collected from two zoo populations in Australia (Perth Zoo, Monarto Zoo) and a rehabilitation facility in South
Africa. See Chapter 2 for a full description of sample collection methods.
114 Chapter 6 – Detecting Taenia species in…
6.2.2 Parasitological techniques
Refer to Chapter 2 for a detailed description of microscopy methods. All parasite ova and cysts observed were recorded, although only data for taeniid spp. are reported here. All samples were then analysed using PCR protocols specific for taeniid species as described below.
6.2.3 Identification of proglottids
Taeniid proglottids were fixed in 10% formalin and stained using two different methods.
For Semichon’s aceto-carmine stain (Semichon, 1924), proglottids were placed into ethanol for 24 hours, 1 drop of Semichon’s stain was added and after 24 hours samples were dehydrated in a series of ethanol dilutions, starting with 70% ethanol and finishing with 100% ethanol. These were then cleared in methyl salicytate for 20 minutes and mounted onto microscope slides in Canida balsam. For Harris’s haematoxylin stain
(Harris, 1900), formalin fixed proglottids were placed in a dilution (water and 1.5 drops) of
Harris’s haematoxylin overnight, then washed in 70% ethanol before being destained in acid alcohol (2% HCl in 70% ethanol) for several minutes until specimens were pale pink in colour. Destaining was halted in basic alcohol (ammonium hydroxide in 10 ml 70% ethanol) for up to 15 minutes or until samples turned blue. Samples were then washed in
70% ethanol, dehydrated, cleared and mounted on slides as for Semichon’s stain.
Identification of proglottids was made on the morphology of the female genitalia of each proglottid as described by Verster (1969) (Figure 6.2).
115 Chapter 6 – Detecting Taenia species in…
Vas deferens loops Cirrus pouch
Vaginal sphincter muscle Vaginal loops
Figure 6.2 A depiction of the genital atrium of T. crocutae as an example of the morphological features used in identification of proglottids. From Verster (1969).
Appendix 1 displays the proglottid key used for identifying samples obtained in this study.
6.2.4 DNA extraction
A 2 ml aliquot of each ethanol-preserved sample was centrifuged and ethanol eluted. The remaining solid matter was used for DNA extraction using the Maxwell® 16 Instrument
(Promega, Madison, USA) as per the manufacturer’s instruction. In an attempt to reduce the impact of inhibitors in carnivore faecal matter, the final elution was diluted to a 5:1 ratio with nuclease free water.
6.2.5 Amplification of Taeniid isolates at the 12S rRNA locus
A multiplex PCR at the 12S rRNA locus was used for differentiation of Taenia spp.,
Echinoccocus granulosus and E. multilocularis as per Traschel et al. (2007). Briefly, 5 primers (Cest1, Cest2, Cest3, Cest4 and Cest5) were used for amplification yielding a 267 bp product for Taenia sp, 117 bp for E. granulosus and 395 bp for E. multilocularis. The
116 Chapter 6 – Detecting Taenia species in…
PCR reaction was performed in 50 μl volumes consisting of 2µl of extracted DNA, 10
ρmol of each primer, 25 μl of mastermix (Qiagen multiplex kit, Qiagen, Hilden, Germany) and 18 μl H2O. The 267 bp amplicons representing Taenia sp. were sequenced using the internal sequencing primer Cest 5seq, as described by Traschel et al. (2007). The PCR product was purified using a Wizard SV gel and PCR Clean-up system (Promega,
Madison, USA) following the manufacturer’s instructions. Sequence reactions were performed using the Big Dye Terminator Version 3.1 cycle sequencing kit (Applied
Biosystems) according to the manufacturer’s instructions. Reactions were electrophoresed on an ABI 3730 48 capillary machine.
6.2.6 Data analysis
Prevalences of infection were expressed as a percentage of positive samples found by microscopy with 95% confidence intervals calculated assuming a binomial distribution, using the software Quantitative Parasitology 3.0 (Rozsa et al., 2000). Differences in prevalence between populations and years were tested using the Fisher’s exact test or Chi- square test.
Resultant nucleotide sequences were compared with published sequences on NCBI
GenBank using the basic alignment search tool (BLAST). Further sequence analysis conducted using the sequence alignment program Sequencher 4.8™ (Gene Codes
Corporation, Ann Arbor, USA). The levels of sequence differences (D), based on pairwise comparisons, were calculated using the formula D = 1- (M/L), where M is the number of alignment positions at which the two sequences have a base in common and L is the total
117 Chapter 6 – Detecting Taenia species in… number of positions over which the sequences are compared (Chilton et al., 1997). The level of sequence difference was expressed as a percentage.
Phylogenetic analysis was conducted in MEGA 4 (Tamura et al., 2007) using reference sequences for T. multiceps, T. serialis, and E. granulosus (accession numbers GQ228819,
DQ408418, EU219546, DQ104238 and GQ161844 respectively). The neighbour-joining method was used to infer phylogenetic relationships between sequenced isolates and reference sequences, with support for nodes in the phylogeny assessed using a bootstrap test with 1,500 replicates (Saitou and Nei, 1987).
6.3 Results
6.3.1 Prevalence of Infection
Table 6.2 shows the prevalence of infection with taeniid spp. within captive and wild populations. Prevalence of infections with species of taeniid did not differ significantly between the three wild populations (Fisher’s exact tests; Zambia vs. Namibia P=0.4;
Zambia vs. Zimbabwe P=1.00; Namibia vs. Zimbabwe P=0.7). There was a significant difference between pooled data of wild and captive populations as taeniids were not observed in any of the captive populations sampled (Fisher’s exact test, P < 0.0001).
118 Chapter 6 – Detecting Taenia species in…
Table 6.2 Prevalence of taeniids (with 95% confidence intervals in parentheses) detected in faecal samples from wild populations of the African painted dog.
Zimbabwe Zambia Namibia Total wild Total captive
(n=12) (n=43) (n=28) (n=83) (n=130)
33% 35% 25% 31.3% 0 (12 – 63%) (22 – 50%) (12 – 44%) (22 – 42%)
Data was obtained over three years for the Zambian population and two years for the
Namibian population. Taeniids were observed in each year with prevalences ranging from
14% to 89% (Table 6.3). There were significant differences in prevalences among years within the Zambian population (χ2 = 15.03, P=0.001) but not in the Namibian population
(Fisher’s exact test, P=0.9).
Table 6.3 Prevalence of taeniids observed in the Zambian and Namibian populations of the
African painted dog over a three year period. Sample size (n) and 95% confidence intervals in parentheses.
Population Year
2007 2008 2009
Zambia 89% (n=9) 25% (n=20) 14% (n=14)
(56 – 99%) (10 – 47%) (26 – 43%)
Namibia 26.3% (n=19) 22% (n=9) -
(11 – 50%) (41 – 56%)
119 Chapter 6 – Detecting Taenia species in…
6.3.2 Identification of taeniid spp. proglottids
Five of the nine proglottids obtained from two packs within Zambia were tentatively identified using the morphological features of the female genital atrium, including the presence/absence of a vaginal sphincter muscle and the number of loops in the vas deferens and vagina (Figure 6.2). Table 6.4 lists the morphological data for each of the five proglottids. Using the criteria of Verster (1969) and Jones and Khalil (1984), one proglottid resembled that of T. hydatigena, two resembled T. crocutae, one resembled T. ovis and one resembled T. dinniki.
Table 6.4 Species identification of taeniid proglottids obtained from painted dog populations.
Population Isolate Host Host Morphological characters Probable sex age species
Zambia ZKa01 M Yearling Vaginal sphincter = full T. dinniki Vaginal loops = 2 Vas deferens loop = 2/3 bunched towards end of cirrus pouch Zambia ZKa06 F Yearling Vaginal sphincter = full T. ovis Vaginal loops =0 Vas deferens loops = 2 Zambia ZKa08 ? ? Vaginal sphincter = full T. crocutae Vaginal loops = 1 Vas deferens loops = 3 Zambia ZRh18 M Adult Vaginal sphincter = 0 T. hydatigena Vaginal loops = 1 Vas deferens loops = 2 Zambia ZRh26 ? ? Vaginal sphincter = full T. crocutae Vaginal loops = 1 Vas deferens loops = 3
120 Chapter 6 – Detecting Taenia species in…
6.3.3 Molecular characterisation of taeniid sp. isolates
The multiplex PCR used in this study was able to differentiate between Taenia spp., E. granulosus and E. multilocularis at the 12S rRNA locus (Figure 6.3).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Figure 6.3 Multiplex PCR of taeniid isolates from wild painted dog populations at the 12S rRNA locus. Lanes 2-11 are painted dog samples from Zambia and Namibia. Lane 13 is the negative control; 14-16 are the positive controls for Taenia sp, E. granulosis and E. multilocularis.
Of the 26 samples identified positive for taeniid ova by microscopy, 22 were successfully amplified using the multiplex PCR. All of these were species of Taenia. Of the 22 amplicons, 16 were sequenced. Comparisons to published sequences on NCBI GenBank revealed 3 sequences to be similar to T. hydatigena and 13 to have a similar identity to both T.multiceps and T.serialis (Table 6.5).
121 Chapter 6 – Detecting Taenia species in…
Table 6.5 Genotypic characterisation of taeniid spp. species isolates obtained from wild populations of the African painted dog within Zambia, Namibia and Zimbabwe.
Percentages shown for matched identities with published sequences on GenBank in parentheses.
Population Isolate No Host sex Host age Taenia species
Zambia Z-Ka01 M Yearling T. serialis (96) T. multiceps (96) Zambia Z-Ka02 F Adult T. serialis (96) T. multiceps (96) Zambia Z-Ka05 F Adult T.serialis (96) T. multiceps (96) Zambia Z-Ka06 F Yearling T. serialis (96) T. multiceps (96) Zambia Z-L01 F Adult T. serialis (96) T. multiceps (96) Zambia Z-G01 F Adult T. serialis (89) T. multiceps (89) Zambia Z-Rh01 M Adult T. hydatigena (99) Zambia Z-Rh14 M Adult T. serialis (96) T. multiceps (96) Zambia Z-Rh18 M Adult T. hydatigena (96) Zambia Z-Rh29 F Adult T. hydatigena (89) Namibia N-K17 ? Adult T. serialis (95) T. multiceps (97) Namibia N-B08 ? ? T. serialis (95) T. multiceps (97) Namibia N-T15 ? ? T. serialis (95) T. multiceps (97) Zimbabwe Zw-Mo14 F pup T. serialis (95) T. multiceps (95) Zimbabwe Zw-Mo12 ? ? T. serialis (89) T. multiceps (90) Zimbabwe Zw-Ui01 M ? T. serialis (95) T. multiceps (96)
122 Chapter 6 – Detecting Taenia species in…
To clarify these BLAST results, nine sequences which had minimal ambiguities and maximum bp regions were aligned against reference sequences for T. serialis and T. multiceps, using the alignment program Sequencher 4.8 ™. Single nucleotide polymorphisms (SNP’s) were identified between the two geographic regions and also between the painted dog isolates and the reference sequences (Table 6.6).
Table 6.6 Summary of the nucleotide variations detected between taeniid isolates from
Zambian and Namibian populations of the African painted dog and reference sequences for
T. multiceps and T. serialis (GenBank accession numbers GQ228818, DQ408418 and
EU219546, DQ104238). Alignment was conducted in Sequencher™ 4.8 and dots indicate identity with the first sequence.
Taenia isolates Alignment position
487 492 493 496 524 577 594 612
T. multiceps A A T G G C G T
T. serialis . . . . . T . .
Z-Rh14 – Zambia T G T A A T . C
Z-Ka06 – Zambia T G T A A T . C
Z-Ka02 – Zambia T G T A A T . C
Z-L01 – Zambia T G T A A T . C
Z-Ka01 – Zambia T G T A A T . C
Z-Ka05 – Zambia T G T A A T . C
N-B08 – Namibia T G C A A C A T
N-K17 – Namibia T G C A A C A T
N-T15 – Namibia T G C A A C A T
123 Chapter 6 – Detecting Taenia species in…
Intraspecific variation was calculated using pairwise comparisons (Table 6.7). Low
intraspecific variation was detected within T.multiceps and T.serialis reference
sequences (0 – 0.6%) and within Zambian and Namibian isolates (0.5 – 0.9%).
Pairwise comparisons between the painted dog isolates from both populations and the
reference sequences were somewhat higher (3.0 – 4.9%).
Table 6.7 Pairwise comparison of sequence variation (%) within the 12S rRNA loci of
T. multiceps and T. serialis reference sequences and taeniid isolates obtained from
Namibian and Zambian populations of the African painted dog.
T.multiceps T.serialis Zambian Namibian
isolates isolates
T. multiceps (n=2) 0 4.1 3 – 3.5 2.9 – 3.9
T. serialis (n=2) - 0.6 3 – 3.5 3.9 - 4.9
Zambian isolates (n=6) - - 0 – 0.5 2.5 - 4
Namibian isolates (n=3) - - - 0 – 0.9
T. multiceps (accession numbers GQ228819, DQ408418), T. serialis (accession numbers EU219546, DQ104238), Zambian isolates (Z-Ka01, Z-Ka02, Z-Ka05, Z-
Ka06, Z-L01, Z-Rh14), Namibian isolates (N-T15, N-K17, N-B08).
6.3.4 Phylogenetic analysis of Taenia spp. isolates
Figure 6.4 represents the phylogenetic relationship between the sequenced isolates from
this study and reference sequences obtained from GenBank for several species of
Taenia. Geographic grouping can be observed within the painted dog isolates. Isolates
124 Chapter 6 – Detecting Taenia species in…
from the painted dogs are not completely aligned with T. multiceps or T. serialis
suggesting significant variation exists between them.
Figure 6.4 Phylogenetic relationships, inferred using the Neighbour-joining method between taeniid isolates from African painted dogs and reference isolates of T. multiceps and T. serialis based on sequence data of the 12S rRNA locus.
Representatives of Taenia sp. used for comparison are labelled with accession numbers as published on GenBank, with E. granulosus as the out-group. Numbers at nodes refer to bootstrap values (1,500 replicates) > 20%.
6.4 Discussion
Taeniid species were not detected within any of the captive populations of the African
painted dog. This was most likely a reflection of the captive environment which
involves a modified diet of pre-frozen domestic livestock meat and regular anthelmintic
125 Chapter 6 – Detecting Taenia species in…
treatment inhibiting parasite transmission (see Chapter 2). In comparison, the total
prevalence of taeniid spp. observed in the wild study populations was 31.3%. This was
similar to the prevalence reported by van Heerden et al. (1995) in painted dogs (30%).
Studies on competitor species have reported prevalences of 13% in hyaena and 15%
and 58% in lions (Muller-Graf, 1995; Bjork et al., 2000; Engh et al., 2003).
Prevalence of infection in this study was not significantly different between geographic regions, although a significant difference was observed between years in the Zambian population. This was mainly due to the high prevalence observed in the first year of sampling (2007), which also had the majority of samples collected in the wet season.
Taeniid ova are resilient, but prolonged high temperatures can reduce survivability and subsequently transmission rates are decreased (Lawson and Gemmell, 1983). The
higher prevalence observed in the wet season may also be a reflection of increased
predation, leading to heightened transmission rates and subsequent improved host
condition, allowing for an increase in proglottid output (Mettrick and Munro, 1965).
Conclusive identification of Taenia species was not possible for all samples but with
the use of molecular characterisation, morphological data and knowledge of possible
intermediate hosts, some tentative identifications can be made. The molecular
techniques utilized were successful in determining that the taeniid ova identified
through microscopy were not the pathogenic zoonotic genera of Echinococcus but were
all Taenia species. Three isolates identified closely with T. hydatigena, which
correlated with the identification of a proglottid obtained from one of these samples.
Identification of the remaining 13 isolates was undetermined as a BLAST on GenBank
revealed isolates had similar a identity to both T. serialis and T. multiceps. Pairwise
comparisons of intraspecific variation within the reference sequences were low at 0.6%
126 Chapter 6 – Detecting Taenia species in…
for T. serialis and 0% for T. multiceps. In comparison, a much higher variation was
observed between T. multiceps and T. serialis and the Zambian isolates (3.4% and
3.5%) and the Namibian isolates (2.9% and 4.9%). This suggests that the painted dog isolates are genetically distinct from the reference sequences. Additionally, the variation between sequences from each geographic region was equally high (2.5% -
4%). This was also implied in the phylogenetic tree, where the isolates from Zambia and Namibia grouped separately and apart from T. multiceps and T. serialis. These results indicate that the taeniid species found in African painted dogs in this study are
not T. multiceps or T. serialis and are most likely an as yet unsequenced African Taenia
species. It would also appear that there are different species infecting the different
geographic regions. The inability to conclusively identify these isolates is most likely
due to the lack of genetic information available for the rarer African Taenia species
such as T. crocutae, T. hyaenae and T. dinniki.
The probability that the infecting species were of African origin was supported with the
identification of proglottids. Whilst the use of only proglottids for the purpose of species identification is not conclusive the morphology of reproductive organs can be characteristic enough to discount some species (Verster, 1969). For example, the presence of a full vaginal sphincter was able to discount T. multiceps as a possible
species as a ½ sphincter (pad) is specific to this species. As all proglottids had either a
full vaginal sphincter or a complete absence of one, this decreased the likelihood that T.
multiceps was the predominant species present as suggested by the molecular data.
Similarly, T. serialis was discounted due to the absence of an extended cirrus pouch
and variation between vaginal sphincters and number of loops in the vagina and vas deferens. Additionally, a proglottid identified as T. dinniki had come from a faecal sample from which the sequenced isolate matched with T. multiceps/T. serialis.
127 Chapter 6 – Detecting Taenia species in…
Without adult worms and/or the addition of molecular data of the rarer African species
of Taenia to public databases, the identification of the predominant Taenia species
infecting these populations remains inconclusive. To date the only species of Taenia
reported in the painted dog have been T. pisiformis, T. s. brauni and T. hyaena
(Ortlepp, 1938; Mahon, 1954; Baer and Fain, 1955). While T. crocutae and T. dinniki are both species previously found in hyaena, they may be shared with painted dogs as is
T. lycaontis (syn. T. hyaenae). The intermediate hosts for T. dinniki are presently
unknown, however, for T. crocutae they include antelope such as impala, lechwe, kudu
and duiker. These intermediate hosts are major food sources for the painted dog with
impala the dominant prey item within the Zambian population and kudu and duiker the
dominant prey item within Namibia (Lines, 2009).
Whilst Echinococcus species were not identified in this study E. granulosus has been
previously reported in the painted dog (Ortlepp, 1934; Nelson and Rausch, 1963;
Verster, 1965; Young, 1975). In particular, experimental infections found painted dogs
to be very susceptible to infection with Echinococcus protoscolices (Verster, 1961).
However, while the painted dog appears to be a suitable host, only a few observations
have been made. This low incidence may be due to the inability to differentiate taeniid
ova or perhaps more likely due to the lack of suitable intermediate hosts acting as prey.
Two studies in Kenya which conducted numerous necropsies on wild herbivores found
very few hydatid cysts within these animals (Nelson and Rausch, 1963; MacPherson et
al., 1983). These same studies presented evidence that the parasite was being
maintained between dogs and domestic livestock rather than sylvatic transmission. A
recent review on known intermediate hosts for hydatid cysts also noted that antelope
appear to play a minor role with very few observations from large sample sizes
128 Chapter 6 – Detecting Taenia species in…
(Huttner et al., 2009). Antelope are a major food source for the painted dogs in this study and this may provide a reason for the absences of Echinococcus spp.
6.4.1 Conclusions
The prevalence of Taenia species observed in this study indicates that the painted dog is an important definitive host for taeniid in all geographic regions sampled. Molecular tools demonstrated that Echinococcus species were not cycling in any of the sampled wild populations and therefore painted dogs should not be implicated in the spread of hydatid disease in these regions. The most prevalent cestodes within all sampled populations are perhaps one or more genetically uncharacterised Taenia species.
Molecularly these appear to be closely related to T. multiceps, a potential zoonotic threat, but morphological data suggests other species such as T. crocutae and T. dinniki are possible, both of which have unknown zoonotic potential. Additionally, there appears to be geographic variation between the Zambian and Namibian isolates. This was the first observation of Taenia hydatigena within the African painted dog and possibly the first observations of T. multiceps and T. dinniki.
Molecular tools are allowing substantial advancements in the efforts to unravel the phylogeny of Taeniidae but further work needs to be done on the lesser known Taenia species of African carnivores. Increased surveillance and sample collection from wild populations, combined with molecular characterisations will assist in understanding the epidemiology of Taenia infection within this endangered carnivore.
129 Chapter 7 – General discussion
Chapter 7
General discussion
130 Chapter 7 – General discussion
7.1 Conservation status of the African painted dog
As habitat destruction and human encroachment continue, there is an ever increasing
need for conservation of wild species. The African painted dog has suffered a 99%
decline in population size in the last century, with approximately 3,000 animals left in
the wild environment today (IUCN, 2010). As an endangered species, African painted
dogs are more vulnerable to stochastic events such as disease outbreaks which can lead
to extirpations. It is therefore imperative to understand all threatening processes to
which these animals may be exposed. Parasitism is considered one such threatening
process for which a thorough understanding is still lacking.
The main aim of this study was to obtain detailed baseline data of parasitism within populations of the African painted dog in both captive and wild environments. With
this information it was hoped to assist in the conservation of the painted dog by a)
recognising the challenges of parasite control in captive populations, particularly those
involved in reintroduction and/or translocation programs, and b) being able to identify
deviations from ‘baseline’ parasite levels in wild populations which could be
indications for emerging exotic and/or zoonotic diseases.
7.2 Increasing importance of studies of parasites
Parasite/host interactions within the natural environment generally involve
polyparasitism with variable host and environmental factors leading to complex and
dynamic systems. Parasitism within individual hosts and host populations can have
both negative and positive effects. Direct impacts cause disease whilst also develop
host immune systems, and indirect impacts mediate competitive and predatory
131 Chapter 7 – General discussion
interactions, whilst also drive genetic diversity. To add to these complex interactions,
the effects of outside stressors such as habitat destruction and human encroachment are
important influences which can easily disrupt the natural balance of many host/parasite
relationships. To attempt to understand the effects on any particular host species,
comprehensive data must first be obtained on the parasites that are present in natural
host populations, their prevalence and their relationship to host and environmental
variables. This study was successful in obtaining parasitological data on several wild
and captive populations over a three year period and currently represents the largest
parasitological study yet undertaken of the African painted dog.
7.3 Parasitological techniques
The use of traditional microscopy techniques in conjunction with molecular tools to
genetically characterise parasite species was found to be a successful combination for
this project. Microscopy techniques allowed for the identification of the majority of
parasites existing within a specific host along with an estimate of the intensity of
infection for each animal. However, many parasites could not be identified to species
level based on ova/cyst morphology and molecular characterisation was required in
order to obtain this information. Other studies using these techniques include those
which have successfully identified species of hookworm and Giardia in faecal samples
obtained from dogs and coyotes (Traub et al., 2004a; Palmer et al., 2008; Traub et al.,
2008; Thompson et al., 2009). Prior to use of this technology, the most common way to
identify parasite species was by obtaining adult specimens during necropsy of the host,
which still required considerable expertise in order to correctly identify specimens.
Euthanasia and subsequent necropsy is not an option when dealing with endangered wildlife and finding animals which have died of natural causes in the field is extremely
132 Chapter 7 – General discussion
rare due to the efficiency of scavengers. Molecular techniques are therefore vital to
conduct complete parasitological diagnostics within endangered, wild populations. The combination of microscopy and molecular methods have allowed this project to provide significant information on parasite infracommunity composition, intensity of infection within populations and also the pathogenic and zoonotic risks posed by species such as
Giardia duodenalis, Taenia spp. and Ancylostoma spp.
7.4 Implications for biodiversity conservation
As discussed in Chapter 1, parasites make up a large part of the biodiversity in natural
ecosystems and have co-evolved to form complex relationships with their host and
surrounding environment (May and Anderson, 1983; Poulin and Morand, 2000).
Therefore, parasites warrant consideration for conservation programs in their own right.
Of particular concern would be species of parasites that are host specific and run the
risk of becoming extinct with the host. With reference to this study some parasite
species could not be completely identified, leaving the possibility that host specific
parasites exist within painted dog populations. For example, the majority of sequenced
isolates of Taenia spp. obtained from wild populations were not completely matched
with the available genetic information. It is possible that the species of Taenia infecting
these animals are known species which are not yet genetically characterized or they
could be previously unidentified species unique to the painted dog. As the painted dog
is an endangered carnivore, the risks of co-extinction events occurring with this host
are significant. It is possible that there is the risk of losing species before science has
even been introduced to them.
133 Chapter 7 – General discussion
7.5 Parasitism in natural populations
7.5.1 Baseline data
This study has gained an insight into the natural abundance, prevalence and intensity of parasitism within wild populations of the painted dogs over several geographic regions.
The similar parasite community compositions observed among all three wild populations during the three year study suggest that this represents the ‘natural’ parasite
fauna of the African painted dog. These data can therefore be confidently used as a
baseline for the GI parasites infecting wild populations of the African painted dog, and
can be used for comparisons with future results. Few studies have been able to obtain
this information with most conducting single random sampling studies which are
unable to provide comprehensive data on the host/parasite systems. The need for this
data has been noted by several authors of similar studies who have only been able to
conduct single studies on small population, such as those conducted on the African lion
and spotted hyaena (Bjork et al., 2000; Engh et al., 2003)
Of the seven GI parasite genera observed in populations of the African painted dog,
five have not been previously reported. Within the two genera previously reported
(Taenia and Ancylostoma), three species are reported here for the first time
(Ancylostoma braziliense, Taenia hydatigena and T. dinniki). This large proportion of
new discoveries demonstrates the paucity of information currently available on
parasitism within this host species and is a reflection of the limited knowledge of parasitism in wildlife in general.
134 Chapter 7 – General discussion
7.5.2 Parasite threats to painted dogs
The ecology of the African painted dog plays a pivotal role in its exposure to parasitic
disease and potential disease outbreak within populations. Social aspects of the pack
such as the maintenance of close contact by all animals can lead to the rapid spread of
directly transmitted parasites such as hookworm and Giardia spp. Likewise, feeding on
the same prey items results in the same exposure to indirectly transmitted parasites such
as Sarcocystis spp. and Taenia spp. Painted dog packs are renowned for having large
roaming areas (<2,000 km2) which raises the likelihood of packs moving through
human communities and contracting disease from domestic animals, particularly
domestic dogs. The exposure of one member of the pack to disease will then be likely
to result in all members becoming infected. Finally, as populations of painted dogs
appear to exist at natural low densities they are particularly vulnerable to catastrophic
events such as disease which can result in local extinction.
It was difficult to ascertain clinical effects of parasitism within wild populations as visually all animals appeared to be strong and robust. The only obvious clinical signs were from those animals carrying injuries i.e. broken legs or snare line injuries. This appearance of apparent health is common within the natural environment as most wild animals tend to manifest few recognizable signs of disease (Sachs and Sachs, 1968;
Young, 1969; Roberts et al., 2002). The effects of parasitism on the African painted dog are therefore most likely to be at a subclinical level. With reference to the findings in this project, parasites such as Giardia duodenalis could result in sub-clinical disease, particularly on populations with a low nutritional status or during periods of stress.
Likewise, the intensity of hookworm infection may cause clinical disease in immunocompromised animals, such as old, injured or stressed individuals. Evidence for this has been seen in the death of an immunocompromised captive painted dog due
135 Chapter 7 – General discussion to a hookworm infection, and stress has been suggested as a cause for clinical babesiosis observed in wild rhinoceros and lion (van Heerden, 1986; Penzhorn, 2006).
7.5.3 Zoonoses/anthropozoonoses
Wildlife are often implicated as reservoirs for zoonotic disease and are therefore considered a threat to surrounding human communities and livestock. The results from this study suggest the painted dog is not a major threat for zoonotic disease. Of the parasites observed, the taeniids, Giardia duodenalis and hookworm are potential zoonotic threats. Within the taeniids, the genus Echinococcus is considered the more pathogenic as it can cause hydatid disease in humans. Although there was no evidence of this genus in any of the wild populations of painted dogs which were sampled, the unidentified Taenia spp. cannot be discounted as potential zoonoses.
The observation of the zoonotic assemblages of G. duodenalis in wild populations raised the question of whether painted dogs may transmit this parasite to people, but given the lack of direct contact between these animals and humans, transmission from painted dogs is unlikely. However, increased human activity into areas such as national parks has the potential to increase the prevalence of G. duodenalis infection in the painted dog. Human to animal transmission (anthropozoonotic) is not well understood or recognised but there has been some evidence for this occurring. Examples include the transmission of Giardia spp. from human faecal contamination into populations of gorillas in Uganda and beavers in North America (Bemrick and Erlandsen, 1988;
Graczyk et al., 2002; Fayer et al., 2006). Similarly, the observation of Ancylostoma braziliense in this study indicates a zoonotic risk but again the lack of direct human contact would indicate the risk of transmission from painted dogs in the wild environment would be minimal.
136 Chapter 7 – General discussion
7.6 Parasitism in captive populations
This is one of few studies to directly compare levels of parasitism between captive and
wild environments in a specific host. A significant difference was observed between the
two environments with 15% of captive and 99% of wild animals found to be host to
one or more parasite species. The implications of the lower exposure to parasites
observed in captive populations may be significant, particularly for those involved in
reintroduction programs, as immunologically naïve animals will be more susceptible to
clinical disease (Viggers et al., 1993; Kock et al., 2010).
The management of captive animals is governed by the need for healthy and
reproductively sound animals and therefore parasite control is a major consideration.
Often the objective is to completely eradicate all parasites from the resident populations
but this may also result in extinction of host-specific parasites (Gompper and Williams,
1998). Additionally, as captive breeding facilities move toward conducting
reintroduction programs, management of captive animals may need to alter the focus
from complete parasite eradication to allowing a low level of parasitism to exist within
the population. In the short term this may assist in the development and maintenance of
host immunity which will be required when animals are reintroduced back into the wild
environment. The most pertinent example of this that is relevant to this study is the
observed prevalence of hookworm in the wild environment (32.5%) compared to the
complete absence in the captive environment. Exposure to a large burden of hookworm
by immunologically naïve painted dogs would most likely result in severe anaemia and
possible death as seen in domestic dogs (Miller, 1971; Carroll and Grove, 1985).
However, if captive animals had prior exposure to this parasite and had developed low levels of immunity this effect would be minimized (Carroll and Grove, 1985). In the long term, parasite exposure has been shown to assist in maintaining genetic diversity,
137 Chapter 7 – General discussion
particularly of the major histocompatibility complex (MHC) which is largely involved in immune function (Paterson et al., 1998). As a major concern of captive breeding is loss of genetic diversity this beneficial effect of parasitism may outweigh the occasional loss of an animal due to the direct effects of parasitism.
7.7 Project limitations and future research
7.7.1 Sample collection and analysis
The logistics of field work prevented sufficient sampling of all wild populations in
order to answer all hypotheses. For example, the lack of samples from pups did not
allow for the significance of host age to be sufficiently tested. In addition, sampling was predominantly restricted to faecal samples and it was therefore not possible to
detect parasites such as Toxoplasma spp., Sarcocystis spp., Babesia spp, and
Dirofilaria immitis (heartworm) existing in host blood or tissues.
The use of fresh samples is preferred for accurate detection of parasite stages but the lack of facilities in the field meant that samples had to be preserved in 10% formalin and 70% ethanol for shipping and later analysis. Several microscopy techniques were employed in an effort to observe all parasite species, however, the most accurate method for prevalence data is usually obtained during necropsy. This method was not an option for studies on endangered wildlife and finding carcasses in the field did not
occur during the course of the project.
The molecular techniques employed were of great value in identifying several parasite
species, however not all positive samples could be amplified by PCR. In the case of
138 Chapter 7 – General discussion
hookworm only a small subset of samples was successfully amplified and sequenced.
Additional sequences would have been beneficial in providing detailed information on
the prevalence of species infecting packs and also in obtaining accurate geographic
distributions for the hookworm species observed. Finally, as the use of molecular
techniques is relatively new not all species of parasites have been genetically characterised and sequences are therefore not available for comparison in databases.
This was the case with the predominant Taenia spp. observed in this study which remains unknown despite the successful amplification and sequencing of many samples.
7.7.2 Continued surveillance
The data obtained from this study has provided a baseline for the ‘normal’ parasite diversity and prevalence of GI parasites to which painted dogs are exposed within the natural environment. This information can now be used to identify future deviations from this baseline which may then assist to identify potential emerging disease. In order for this to be of use, continued surveillance of parasitism within painted dog populations needs to be conducted. The data from this study, used in conjunction with results from future surveillance, may also help to predict how continued pressure on the already small populations existing in the wild may change the dynamics of the host/parasite systems currently in play. The host/parasite relationship is often a careful balance which can be tipped in favour of the parasite if the host is immunologically compromised. For instance, the decreased hunting success in small painted dog packs may lead to a lowered nutrition plane which could in turn lead to immunocompromised animals. Other factors such as habitat destruction, human encroachment and disease may also result in an imbalance in the host/parasite relationship leading to an increase in clinical disease.
139 Chapter 7 – General discussion
7.7.3 Threat of emerging disease
As outlined throughout this thesis the host/parasite interaction is complex and dynamic.
These interactions will be further complicated by human influences such as habitat
destruction and human encroachment. Habitat destruction disturbs ecosystems and can
subsequently alter host/parasite interactions. Evidence for this was seen in a study by
Gillespie et al. (2005) which identified altered patterns of parasite infection among red
tailed guenon populations living in unlogged and logged habitats. Likewise, human
encroachment brings the increased risk of disease spillover from co-habiting domestic
animals. As approximately 80% of domestic animal pathogens can infect wildlife the
threat is significant (Cleaveland et al., 2001). The painted dog has already been seen to
be vulnerable to domestic dog diseases such as rabies and canine distemper virus
suggesting they could be vulnerable to additional disease spillover (Kat et al., 1995;
Roelke-Parker et al., 1996). The identification in this study of predominantly zoonotic
assemblages of Giardia duodenalis in the painted dog may be indicative of human
encroachment and consequently should be considered an emerging disease within this
species. Future parasitological studies comparing results to this newly obtained baseline
may be able to predict and identify future emerging diseases.
7.7.4 Captive management
This project was only able to conduct a captive versus wild comparison for a single
host species but given the significance of results obtained, could be used as a model for
other host species. As reintroduction programs become a main aim for many captive
facilities a host specific knowledge of parasitism in the natural environment may
provide important information. The ability to predict the type of parasitic challenge that
reintroduced hosts may face could lead to vaccination programs or deliberate exposure
to specific parasites in order to increase the chance of successful reintroduction.
140 Chapter 7 – General discussion
Additionally, these parasitological studies may prevent future introductions of exotic pathogens from reintroduced captive stock into naïve wild populations (Viggers et al.,
1993; Kock et al., 2010). Similar studies on other endangered captive host species could, therefore, be of benefit to many reintroduction and/or translocation programs.
141
Appendix 1. Taenia spp. proglottid key. From Verster (1969)
142
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