Evaluation of the role of rats as reservoir hosts for fishborne zoonotic trematodes in two endemic northern Vietnam fish farms
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Fishborne zoonotic trematodes (FZTs) pose a food safety risk for the aquaculture industry in Vietnam. The risk of being infected from eating raw fish applies not only to humans but also to domestic animals which can serve as reservoir hosts in fish farms. The role of rodents, commonly found in fish farms, as reservoir hosts has not been adequately evaluated. To study this question, commensal and rice field rats were collected from fish farms in Nghia Lac and Nghia Phu communes, Nam Dinh province, Vietnam and examined for FZT infection. A total of 250 rats (Rattus norvegicus, Rattus argentiventer, and Bandicota indica) were collected and examined; the rats were trapped in the farm households (commensal) and in rice fields adjoining the fish ponds (field). The total prevalence of all parasites was 52.8 %: nematodes, 42.4 %; trematodes 18.0 %; and cestodes, (3.6 %), including two zoonotic cestode species, Raillietina celebenisis and Hymenolepis diminuta. Although overall prevalence and intensity of parasite infection did not differ significantly among rat species or between the two communes, the intensity of nematode infection was significantly higher in commensal rats (p < 0.05). The only FZTs recovered were the intestinal flukes Echinostoma cinetorchis and Centrocestus formosanus, both at low prevalence. Because the most common FZTs found in fish from these communes are Haplorchis pumilio and Haplorchis taichui, neither of which were found in the rats, we conclude that rats are not significant reservoir hosts for FZT in these Vietnamese fish farms.
KeywordsRice Field Farm Household Fish Pond Reservoir Host Farm Pond
The authors appreciate the cooperation extended by the farmers who participated in this study. We are grateful to Dr. Nguyen Truong Son, Institute of Ecology and Biological Resources, Vietnamese Academy of Science and Technology, Hanoi for help on identification of the rats. Appreciation is also expressed to Dr. Van Thi Phan, Director of the Fibozopa Project in Vietnam for her strong support of the study. The Danish International Development Assistance (Danida) is gratefully acknowledged for its financial support to this study through the project titled “Fish Borne Zoonotic Parasite in Vietnam” (http://fibozopa.ria1.org). We thank Patricia Pilitt of the US National Parasite Collection for assisting in access to comparative specimens used in confirmation of identification for some parasites.
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