VECTOR BORNE PARASITIC AND VIRAL DISEASES – Module 1
Leishmaniases: Reservoir hosts
Carla Maia DVM, MSc, PhD, DipEVPC, EBVS® European Veterinary Specialist in Parasitology Global Health and Tropical Medicine. Medical Parasitology Unit. Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa [email protected]
C. Maia
C. Maia The aim of this presentation is to learn:
Definition of a reservoir host of Leishmania sp.
Identify the proven (and some of the suspected) reservoir hosts of visceral and cutaneous leishmaniases in the Old and New Worlds
Leishmaniases
• Worldwide phlebotomine sand fly-borne diseases
caused by protozoa belonging to genus Leishmania
• 21 Leishmania spp. pathogenic for humans
• Diverse clinical manifestations:
(In: http://www.parasitologie.univ-montp1.fr/leishmania.htm)
Visceral leishmaniasis (VL) caused by parasites of the L. donovani J. Oliveira
complex (L. donovani Old World, L. infantum Old + New Worlds)
Cutaneous (CL) or mucocutaneous (MCL) leishmaniasis caused by
Leishmania spp.
• Endemic in >100 countries; 1 billion people at risk
• Incidence of 0.2 to 0.4 million VL cases and 0.7 to 1.3 million CL cases L. Varandas Reservoir host of leishmaniases = a mammal in which Leishmania survives persistently in a way that it may serve as a source of parasites to the vectors
Leishmaniases can be grouped into two broad epidemiological categories according to the source of human infection:
Zoonotic leishmaniases → reservoir hosts are wild or domestic animals and humans play a
role of an accidental host
Anthroponotic leishmaniases → man is the sole reservoir host and source of vector’s infection A “good” reservoir host should:
Be susceptible to the parasites
Live in close contact with man (or any other reservoir host)
Be a good source of parasites to the vectors Provide a significant food source for the vectors and both should rest and breed in the same habitat
Infection should present a chronic evolution allowing the animal to survive at least until the next transmission season
Leishmania parasites identified in reservoir hosts biochemically and genetically the same as those in
humans Be aware that:
The mere presence of the infection in a particular mammal
species, even in large numbers Does not indicate that it is a reservoir host The mere detection of Leishmania DNA in the tissues of a
particular mammal species
In order to incriminate a reservoir host → demonstration that the parasite population depends on that particular mammal for its long-term maintenance When more than one host species can be infected, they can be divided on epidemiological grounds:
Primary reservoir host → responsible for maintaining the parasite indefinitely in nature. Infection is
normally without clinical signs
Secondary (or minor) reservoir host → can transmit infection but cannot maintain parasite
transmission in the absence of the primary host(s)
Accidental (or incidental) host → can be infected but has no role in the maintenance of the
ecological system Anthroponosis Anthroponotic Leishmaniases
Humans are reservoir hosts in two forms of the disease:
VL caused by L. donovani in Indian subcontinent (Bangladesh, India and Nepal) and East Africa
(Djibouti, Ethiopia, Eritrea, Kenya, Somalia, South Sudan, Sudan and Uganda)
CL caused by L. tropica in semi-arid subtropical regions from south-east Turkey to north-west of India
Small foci: Arabia, Ethiopia, Greece, Namibia, North Africa (Algeria, Egypt, Morocco and Tunisia) and Central Asia Boelaert & Sundar, 2017 Foci with few/sporadic cases, disease known/suspected to be zoonotic:
Rock hyraxes (Procavia North African gundi (Ctenodactylus
capensis) in Israel gundi) in the Maghreb
https://en.wikipedia.org/wiki/Rock_hyrax https://en.wikipedia.org/wiki/Comm on_gundi Zoonotic Visceral Leishmaniasis
L. infantum (syn. of L. chagasi) in Central and South America, the Mediterranean basin, Middle East and
Asia
Primary domestic reservoir hosts: Dogs (Canis lupus familiaris)
C. Maia C. Maia C. Maia Secondary reservoir hosts → Transmission of infection confirmed by xenodiagnoses: black rats, hares and wild rabbits ?
Zoonotic Visceral Leishmaniasis
Suggested sylvatic reservoir hosts : Wild carnivores (i.e. foxes (Vulpes spp. and Cerdocyon thous), jackals (Canis aureus), wolves (Canis lupus) and raccoon dogs (Nyctereutes procyonoides)) → no strong evidence as an important source of infection → infectiousness to the vectors to be confirmed ?
Naturally susceptible to infection by L. infantum, normally without development of clinical signs
(when present usually cutaneous; systemic involvement also recorded)
Blood source for some Leishmania vectors
Present parasites in an available way to infect the vector Maia et al. 2015 Among the most popular pets, present in peri/domestic transmission cycles occur
Parasites isolated from infected cats biochemically and genetically identical to the ones obtained
from humans and dogs with leishmaniases
Epidemiological importance in leishmaniasis poorly understood
https://www.writelikenooneswatching.com/2014/02/cats-and- children.html/ Leishmania (Mundinia) martiniquensis Zoonosis?
Previously known as “Leishmania siamensis” (nomen nudum)
Sporadic autochthonous equine and bovine CL has been reported in Germany, Switzerland and in the USA
→ wide geographical distribution
Human cases of VL and CL with/out other co-immunosupressive states in Thailand and Myanmar
Zoonotic potential has been suggested → parasite DNA in liver and spleen samples of black rats
collected in an area where VL cases have been reported Zoonotic Cutaneous Leishmaniases – Old World
L. major from India through Central Asia, the Middle East, to North and West Africa
Reservoir hosts: rodent species
• Great gerbil (Rhombomys opimus) in central Asia, northern Afghanistan and Iran
• Indian desert jird (Meriones hurrianae) in India
• Fat sand-rat (Psammomyus obesus) and Sundevall's jird (Meriones crassus) in northern Africa and
Middle East; Shaw's jird (Meriones shawi) in Morocco and Tunisia
• Libyan jird (Meriones libycus) in the Arabian peninsula and central Asia
• Short-tailed bandicoot rat (Nesokia indica) in Iran
• Arvicanthis, Tatera, Mastomys or Xerus spp. in sub-Saharan Africa
• Voles (Microtus tristrami and Microtus guentheri) in Israel Zoonotic Cutaneous Leishmaniases – Old World Boelaert & Sundar, 2017
L. aethiopica highlands of East Africa (Ethiopia, Kenya and Uganda)
Reservoir hosts: hyraxes (Procavia capensis and Heterohyrax brucei)
L. infantum throughout the Mediterranean Basin C. Maia
Reservoir hosts: dogs https://en.wikipedia.org/wiki/Rock_hyrax
L. Campino Zoonotic Cutaneous Leishmaniases – New World
L. amazonensis (syn. of L. garnhami) in Argentina, Bolivia, Brazil, Colombia,
Costa Rica, Ecuador, French Guyana, Peru, Suriname and Venezuela
Reservoir hosts: ground-dwelling rodents
Suspected/putative secondary reservoir hosts: several wild mammals
Hairy-tailed bolo mouse (Necromys lasiurus)
https://en.wikipedia.org/wiki/Hairy-tailed_bolo_mouse
Boelaert & Sundar, 2017 Zoonotic Cutaneous and Mucocutaneous Leishmaniases – New World
L. braziliensis countries of Central and South America
Sylvatic reservoir hosts: bats, edentates, marsupials, wild rodents
Tate’s woolly mouse opossum (Marmosa Flat-faced fruit-eating bat (Artibeus paraguayana) planirostris)
https://www.who.int/leishmaniasis/mucocutaneous_leishmaniasis/en/ Common opossum (Didelphis marsupialis)
https://www.pinterest.fr/pin/346917977525671665
https://www.sarem.org.ar/en/conservation-committee/artibeus-planirostris-en/ https://en.wikipedia.org/wiki/Common_opossum
Suspected domestic reservoir hosts (rural areas): equids, dogs and cats ?
Suspected reservoir hosts (outbreaks): humans Zoonotic Cutaneous Leishmaniases – New World
L. colombiensis in Colombia, Panama and Venezuela
Reservoir host: Hoffmann's two-toed sloth (Choloepus hoffmanni)
https://en.wikipedia.org/wiki/Hoffmann%27s_two-toed_sloth
L. guyanensis in Argentina, Bolivia, Brazil (some states), Colombia, Ecuador, French Guiana, Guyana,
Peru, Suriname and Venezuela
Reservoir host: Linnaeus's two-toed sloth (Choloepus didactylus)
https://en.wikipedia.org/wiki/Linnaeus%27s_two-toed_sloth Zoonotic Cutaneous Leishmaniases – New World
L. lainsoni in Bolivia (subtropical areas), Brazil (some states), Ecuador,
French Guiana, Peru (tropical areas) and Suriname
Suspected reservoir host: Lowland paca (Cuniculus paca)
By Marcos Antonio Vieira de Freitas - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=60064430 L. mexicana (syn. of L. pifanoi) in Belize, Colombia, Costa Rica, Ecuador, Guatemala, Mexico, southern USA and Venezuela
Reservoir hosts: Ground-dwelling rodents (Heteromys, Neotoma, Nyctomys, Ototylomys and Sigmodon Big-eared climbing rat (Ototylomys phyllotis) spp.)
Boelaert & Sundar, 2017 https://www.inaturalist.org/taxa/45025-Ototylomys-phyllotis
Zoonotic Cutaneous Leishmaniases – New World
L. naiffi in Brazil (Rondônia state), Ecuador, Suriname and French Guiana
banded_armadillo
- Nine
Reservoir host: Nine-banded armadillo (Dasypus novemcinctus) /wiki/ https://en.wikipedia.org
L. panamensis in Colombia, Costa Rica, Ecuador (Pacific littoral), Guatemala, Honduras, Nicaragua and
South American coati (Nasua Panama nasua)
Reservoir hosts: sloths Saguinus Saguinus
Suspected reservoir hosts: coatis, monkeys, rodents
https://pt.wikipedia.org/wiki/Quati-de-cauda-anelada )
Suspected reservoir hosts (outbreaks): humans
Geoffroy’s tamarin( Geoffroy’s geoffroyi
https://pt.wikipedia.org/wiki/Saguinus_geoffroyi ? Zoonotic Cutaneous Leishmaniases – New World
L. peruviana in Peruvian Andes ? Suspected sylvatic reservoir hosts: marsupials and rodents
Suspected peri/domestic reservoir host: dog
L. shawi in Brazil (Atlantic rainforest of Pará State)
Sylvatic reservoir hosts: coatis, monkeys and sloths
L. venezuelensis in Venezuela ?
Suspected domestic reservoir host: cat Take home message:
Reservoir host of leishmaniases = a mammal in which Leishmania survives persistently in a way that it
may serve as a source of parasites to the vectors
. Primary reservoir host → responsible for maintaining the parasite indefinitely in nature
. Secondary reservoir host → can transmit infection but cannot maintain parasite transmission in the
absence of the primary host(s)
The mere presence of the infection in a particular mammal species
The mere detection of Leishmania DNA in the tissues of a particular mammal species
Does not indicate that this mammal is a reservoir host Take home message:
Leishmania spp. have been found in a variety of wild and domestic animals but their role in the life
cycle of the parasite is unknown
To determine the role of a suspected reservoir host in the maintenance and transmission of Leishmania
spp. pathogenic to humans:
Isolation and genetical and biochemical characterization of the parasites from samples
accessible to the vectors
Evaluation of their infectiousness to vectors (i.e. xenodiagnosis)
→ Other factors: food sources, longevity, movement and migration activities Selected references
. Alvar J et al. (2012) Leishmaniasis worldwide and global estimates of its incidence. PLoS ONE 7(5):e35671
. Aoun K, Bouratbine A (2014) Cutaneous leishmaniasis in North Africa: a review. Parasite 21:14
. Ashford RW (2000) The leishmaniases as emerging and reemerging zoonoses. Int J Parasitol 30(12–13):1269-81
. Gramiccia M, Gradoni L (2005) The current status of zoonotic leishmaniases and approaches to disease control. Int J Parasitol
35(11-12):1169-80
. Maia C, Dantas-Torres F, Campino L (2018) Parasite Biology: The Reservoir Hosts. In: The Leishmaniases: Old Neglected
Tropical Diseases. Ed: F. Bruschi, L. Gradoni. Springer International Publishing. Viena. Austria, pp 79-106
. Quinnell R, Courtenay O (2009) Transmission, reservoir hosts and control of zoonotic visceral leishmaniasis. Parasitology
136(14):1915-34
. WHO (2010) Control of the Leishmaniasis: Report of the WHO Expert Committee on the Control of Leishmaniases, World
Health Organization. http://www.who.int/neglected_diseases/resources/who_trs_949/en