Public Health Importance of Non-Biting Cyclorrhaphan Flies

Transactions of the Royal Society of Tropical Medicine and Hygiene (2009) 103, 187—191

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Public health importance of non-biting cyclorrhaphan ﬂies

Teshome Fetene a,∗, Netsanet Worku b a Adamitulu ppsc, Research and Development Service, P.O. Box 1206, Addis Ababa, Ethiopia b School of Public Health, Gonder University, P.O. Box 196, Gonder, Ethiopia

Received 22 April 2008; received in revised form 13 August 2008; accepted 13 August 2008 Available online 25 September 2008

KEYWORDS Summary This study was carried out to determine the role of non-biting cyclorrhaphan flies as Cyclorrhaphan flies; carriers of human intestinal parasites at Woreta, northwestern Ethiopia. In total, 6530 flies were Intestinal parasites; collected from four breeding sites and then examined for human intestinal parasites, mainly Helminths; using the formol—ether concentration method. Fly species identified were Musca domestica Protozoa; (32.9%), Chrysomya rufifacies (32.6%), Musca sorbens (23%), Lucina cuprina (4.7%), Calliphora Carrier; vicina (2.8%), Chrysomya bezziana (2.3%) and Wohlfahrtia magnifica (1.7%). Intestinal par- Ethiopia asites such as Ascaris lumbricoides (36.9%), Trichuris trichiura (38.8%), hookworm (13.0%), Hymenolepis nana (0.6%), Taenia spp. (8.4%), Strongyloides stercoralis (1.7%), Entamoeba histolytica/dispar (48.1%), Entamoeba coli (24.7%), Cryptosporidium spp. (16.7%) and Giardia lamblia (10.4%) were isolated from both external and gut contents of the flies. Trichuris trichiura and A. lumbricoides among the helminths and E. histolytica/dispar and E. coli among the protozoans were the dominant parasites identified. It was observed that more parasites were isolated from gut contents than the external surfaces of the flies examined (P < 0.001). Chrysomya rufifacies were found to carry more helminths than M. sorbens and M. domestica. Musca sorbens were the highest carriers of protozoan parasites followed by M. domestica and C. rufifacies. The significance of filth flies as carriers of human intestinal parasites has been highlighted. © 2008 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.

1. Introduction decomposing organic materials.1 The free access of flies to such sites ensures that they are laden with disease- Non-biting flies are equipped with special sensory cells on causing organisms on their mouthparts, body hairs and sticky 2 their antennae that can detect strong compounds such as pads of their feet, stomach, faeces and vomit. Although ammonia and carbon dioxide emitted from faeces and other other routes of transmission, such as contaminated water, carriers and food handlers, might be major possibilities, the likelihood of non-biting flies mechanically transmit- 3 ∗ Corresponding author. ting these parasites cannot be excluded. Several non- E-mail address: [email protected] (T. Fetene). biting cyclorrhaphan flies are involved in the mechanical

0035-9203/$ — see front matter © 2008 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.trstmh.2008.08.010 188 T. Fetene, N. Worku transmission of pathogens in different parts of the species and sex groups, counted and pooled into batches of world.4 10 flies of the same sex and species. Several studies showed that non-biting flies carry different stages of helminths and protozoan parasites. According 2.3. Processing flies for parasite isolation to Sulaiman et al.,5 for example, eggs of Ascaris lumbricoides, Trichuris trichiura and hookworm (Necator Each batch of pooled flies was immersed in sterile physi- americanus) were isolated from Chrysomya, Sarcophaga and ological saline in a separate container and stirred with an Musca fly species collected from refuse dump and perido- applicator stick for 5 min then vortexed for 2—3 min to wash mestic sites. Filth flies were also found to carry cysts of off any parasitic eggs, cysts or larvae from the external body Entamoeba histolytica and eggs of cestodes and different of the flies. nematodes.6 Similarly, Doiz et al.7 incriminated houseflies as These flies were then transferred to other containers in carriers of eggs of Enterobius vermicularis, Toxocara canis, their batches in sterile conditions using forceps and fur- Strongyloides stercoralis and cysts and triphozoites of Enta- ther processed for examination of gut contents. The whole moeba coli, as well as Giardia and Trichomonas spp. gut of each washed fly was dissected out with the others Most protozoan and helminth parasites are prevalent from its batch on an autoclaved microscope slide under a in urban and rural areas of Ethiopia,8,9 affecting the stereoscopic microscope using entomological needles and health of the community. The housefly (Musca domestica), was macerated to liberate the lumen contents. the eye-seeking fly (Musca sorbens) and other filth flies Suspensions from both the external surface and gut have been foraging on and breeding in rubbish and waste content of each fly batch were processed for micro- matter, playing a great role as mechanical carriers of dif- scopic examination using the formol—ether concentration ferent helminths and protozoan parasites in Addis Ababa, method.11 Smears prepared from the concentrations were Ethiopia.3 examined under the microscope using 10× and 40× mag- Therefore, this study was carried out to assess the nifications for helminth ova/larvae and protozoan cysts, significance of non-biting cyclorrhaphan fly species as car- respectively. The data obtained were recorded per batch riers of intestinal human parasites in Woreta, northwestern of pooled flies in reference to the external surface and gut Ethiopia. content of the flies. A modified Ziehl—Neelsen staining method12 was applied 2. Materials and methods for the detection of Cryptosporidium spp. Air-dried smears of the external surface and gut content suspensions were 2.1. Study area fixed with methanol and stained with carbol—fuchsin for 30 min. These were then washed with tap water, decolorized The study was carried out in Woreta, northwestern Ethiopia. with 1% acid alcohol for 1 min, washed with tap water again, Woreta, the capital city of Kemkem District, is located at an counterstained with 1% Methylene Blue for 1 min, rinsed in altitude of 1950 m a.s.l. near Lake Tana, having an annual tap water and then air-dried. The slides were examined precipitation of more than 650 mm per year and an esti- under a microscope to count the number of cysts per batch mated population of 27 563. of pooled flies. In the area, the majority of inhabitants had pit latrines, Species and type of intestinal parasite were identi- which were not properly maintained. Open-air defecation fied based on the description and techniques stated by was commonly observed among children, a few adults and WHO.13 homeless people, particularly in peripheral areas. Small market areas, slaughtering in open fields and inappropri- 2.4. Data analysis ate disposal of wastes are also common in the area. Flies were collected from randomly selected potential foraging Data analysis was carried out using SPSS version 12.0 for Win- and breeding sites, such as rubbish heaps, open defecat- dows. A ␹2 test was used to compare different independent ing grounds, open-air small markets and butcheries, close variables with carriage of the parasites. Degree of para- to human dwellings. site contamination was determined calculating their relative frequencies. A P-value of <0.05 was considered statistically 2.2. Fly collection and identification significant.

Flies were collected monthly for 9 months during the dry season (October 2006—June 2007) from all foraging and 3. Results breeding sites by investigators and field assistants using a sweeping net for 2 h in the morning (9:00 to 11:00 h) when 3.1. Flies and their breeding sites most flies were active. Trapped flies were placed in small groups in plastic bags and test tubes, labelled and trans- In total, 6530 non-biting cyclorrhaphan flies, which pooled ported to the laboratory in a cooler box with ice packs and into 653 batches, were collected from four potential fly stored in the refrigerator at −4 ◦C until identification and breeding sites: butchery, rubbish, market and defecating processing for parasite examination. ground areas (Figure 1). Species of collected flies were identified using refer- The non-biting cyclorrhaphan flies identified in this study ence keys given by Crosskey and Lane.10 All trapped flies area were: M. domestica (32.9%), C. rufifacies (32%), were killed by chloroform and then separated into specified M. sorbens (23%), Lucina cuprina (4.7%), Calliphora vicina Public health importance of non-biting cyclorrhaphan flies 189 Strongyloides ; Hw: hookworm; Ss:

Figure 1 Species composition of non-biting cyclorrhaphan ﬂies in relation to their breeding areas. Hymenolepis nana ; Hn: (2.8%), Chrysomya bezziana (2.35%) and Wohlfahrtia mag- niﬁca (1.7%).

3.2. Parasite species identiﬁed Giardia lamblia The relative burden of helminths and protozoans in 1306

fly batches (653 external surface and 653 gut contents) are ; Gl: summarized in Supplementary Tables 1 and 2, respectively. Both the external surface and gut contents of the flies were positive for helminth and protozoan parasites. Identified helminth parasites were T. trichiura (38.8%), A. lumbricoides (36.9%), hookworm (13.7%), Taenia spp. (8.4%), S. stercoralis (1.7%) and H. nana (0.6%). The protozoan parasites isolated from different species of flies were E. histolytica/dispar (48.1%), E. coli (24.7%), Cryptosporid- ium spp. (16.7%) and G. lamblia (10.4%). Chrysomya rufifacies, M. sorbens and M. domestica were Entamoeba histolytica/dispar found to be more contaminated with one or more intestinal parasites than were other fly species (Table 1): C. rufifa- ; Eh: cies carried more helminths, followed by M. sorbens and M. domestica; M. sorbens carried more protozoan parasites, followed by M. domestica and C. rufifacies. HelminthAl Tt Hw Tae Ss Hn Eh Protozoa Ec Cry Gl Total no. Cum. % Parasite burden in relation to the sex of the flies Entamoeba coli

was investigated, and there was no significant difference . (P = 0.343) in degree of contamination between male and female flies. ; Ec: The results of this study showed a highly significant difference (P < 0.001) in the extent of contamination between external body surface and gut content of flies: the gut con-

tent of the ﬂies was found to contain more parasites than Trichuris trichiura 62362230 3.6 2.6 3.6 4.7 1.5 3.7 2.6 4.1 2.6 1.7 5.4 1.7 0.0 1.7 15.0 1.4 4.1 0.0 0.0 0.0 0.0 0.0 3.9 0.0 0.0 1.1 3.0 2.2 0.6 2.3 6.2 0.8 0.0 0.0 0.0 2.5 2.5 2.2 0.0 1.1 44 21 22 17 71.0 58.3 100.0 56.7 426430300 37.1 27.3 34.2 24.2 25.8 39.7 26.3 31.4 50.0 19.8 33.8 45.0 5.4 0.0 100 40.0 0.0 25.6 0.0 37.2 30.3 29.4 40.9 30.9 22.7 25.9 33.7 32.1 48.9 14.1 378 352 255 88.7 81.9 85.0 did the external surface of the ﬂies. Cryptosporidium ; Cry: 4. Discussion spp.; Tt:

The present study shows that M. domestica, C. rufifacies and Taenia M. sorbens are dominant and abundant species, as shown 3 Relative frequencies of contaminated pooled flies per parasite by Getachew et al. Moreover, it demonstrates that each ; Tae: fly species prefers specific breeding sites. The high abundance of C. rufifacies in butcheries and defecating grounds Ascaris lumbricoides may be due to the scavenger feeding habit of the fly and Table 1 Fly speciesChrysomya rufifacies Musca domestica No. pools examinedMusca sorbens Lucilia cuprina ProportionCalliphora of vicina positive pooled flyChrysomya batches bezziana Wohlfahrtia magnifica TotalAl: 1306 194 190 Positive pools 121 74 20 5 180 132 81 92 1089 83.4 its high preference for liquid faecal matter.14 According to stercoralis 190 T. Fetene, N. Worku

Boonchu et al.,15 pork viscera is more attractive to metal- potential routes of contamination, as the infectious agent lic flies than to Sarcophagidae and Muscidae flies. The high is protected while it is in the gut of the fly and maintained abundance of M. domestica in rubbish dumps is perhaps for a certain periods of time.10 This may increase the impor- due to the ability of the fly to feed on drier food sub- tance of flies as a source of human food contamination, with strates. Human faeces are attractive to houseflies in their the pathogens they carry when landing on it. drier solid state,16 and rubbish provides preferred condi- The study results have revealed that M. sorbens, tions for their breeding.17 Eesa and El-Sibae18 showed that M. domestica and C. rufifacies carry more intestinal par- M. domestica were abundant in rubbish dumps, cattle mar- asites than other flies identified in this area. These flies kets and slaughterhouses. Musca sorbens was abundant in forage predominantly on human faeces,27,30 and if infected market areas, and this may be mainly due to the preference individuals defecate in exposed situations, the flies might of the fly to feed on human secretions19 and faecal material get chance to forage on positive faeces. The authors in market areas and areas where human defecation is left observed overcrowded conditions, lack of proper sanitation exposed.16 and health education, and human faeces were commonly In this study, female flies were more numerous than males seen scattered on the ground in the area. Dipeolu21 demon- at all breeding sites. This may be due to the females’ ability strated that houseflies in low-income areas carried more to locate food and favourable oviposition sites. The study parasitic cysts and eggs than those in high-income residen- indicates that sex does not affect the parasite carriage tial areas. Moreover, filth flies associated with cattle barns potential of the flies, supporting the results of studies car- and municipal landfills have shown that more C. parvum and ried out by Monzon et al.20 and Getachew et al.3, that both G. lamblia were carried by flies from cattle barns.29 sexes have equal significance in intestinal parasite transmis- The external body parts of flies (antennae, mouth- sion. parts and legs), and their gut contents, vomit and faeces The present work shows that non-biting cyclorrhaphan carry pathogens that cause diseases.25 The present study flies carry A. lumbricoides, T. trichiura, S. stercoralis, demonstrates that non-biting cyclorrhaphan flies carry eggs, H. nana and Taenia spp., and E. histolytica, E. coli, G. lam- larvae and cysts of intestinal parasites naturally acquired blia and Cryptosporidium spp. Thus, this indicates that filth from unhygienic sources. Thus they can be involved in flies with access to substrates containing these parasites the deposition of these parasites on visited surfaces. can contaminate themselves and the food of inhabitants Mechanical transfer of intestinal parasites by flies could be near the sites where flies have been collected. It has been achieved through defecation, regurgitation or mechanical shown that houseflies caught on rubbish dumps in six areas dislodgement.4,10 of Ibadan (Nigeria) were found to harbour intestinal para- Parasite eggs and cysts adhering to the surface of the sitic cysts and eggs in their alimentary canal, which were fly are quickly removed, because the fly autosterilizes itself similar to those found in the faeces of the community living immediately as it withdraws from the surface on which it in that environment.21 has been feeding.3 This creates favourable conditions for Other studies have shown that non-biting flies carry contaminating human food with the pathogens carried by different stages of helminth and protozoan parasites. For flies when they land on it, and transmission of the parasites example: flies were found to be contaminated with eggs is readily ensured if the food is inadequately cooked and and larvae of Ancylostoma caninum;22 Monzon et al.20 in consumed. Therefore, it is crucial to establish immediate the Philippines and deOliveira et al.23 in Brazil isolated eggs control mechanisms for these flies, through mass education of Ascaris and Trichuris from M. domestica and Chrysomya to improve the standards of sanitation in the area. megacephala; Umeche and Mandah24 obtained ova of A. lumbricoides, S. stercoralis, Ancylostoma doudenale Authors’ contributions: TF and NW conceived and designed 25 and T. canis from M. domestica; Graczyk et al. con- the project and study methodology, carried out the data col- firmed M. domestica as a vector of Sarcocystis spp., lection and analysis, drafted and revised the manuscript, Toxoplasma gondii, Isospora spp., Giardia spp., E. coli, and read and approved the final version. TF is guarantor of E. histolytica, Endolimax nana, Trichomonas spp., Hammon- the paper. dia and Cryptosporidium parvum. Refuse and promiscuous landing synanthropic filth flies were also recognized as trans- Acknowledgements: We are thankful to the staff of the port hosts for Sarcocystis spp.,26 T. gondii,27 Isospora spp. School of Public Health, Gonder University, without whose and Eimeria tenella.28 unreserved cooperation this study could not have been real- Cryptosporidium spp. were detected from both the ized and completed successfully. Similarly we appreciate the external surface and gut content of flies collected at differ- work of the staff of the Department of Research and Devel- ent sites in Woreta. Therefore, this work demonstrates that opment, Gonder University, who appraised and approved the adult flies with access to materials containing the oocysts research. contaminate themselves and carry the parasite. It has been confirmed that filth flies could transport infectious oocysts of C. parvum on their external surfaces and in their digestive Funding: Gonder University, Gonder, Ethiopia, covered all tracts.7,25,29 costs of the research. The gut contents of flies were found to carry more intestinal parasites than the body surface of flies. Experimentally Conflicts of interest: None declared. infected M. domestica carried larvae of A. caninum longer in the gut than on the external surface of the fly.22 Ingestion and defecation of parasites is one of the most important Ethical approval: Not required. Public health importance of non-biting cyclorrhaphan flies 191

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