Fish-borne zoonotic trematodes (FZT) pose a risk to human food safety and health and may cause substantial economic losses in the aquaculture industry. In Nghe An Province, Vietnam, low prevalence of FZT for fi sh farmers but high prevalence for fi sh indicate that reservoir hosts other than humans may play a role in sustaining transmission. To determine whether domestic animals may be reservoir hosts, we assessed prevalence and species composition of FZT infections in dogs, cats, and pigs in a fi sh-farming community in Vietnam. Feces from 35 cats, 80 dogs, and 114 pigs contained small trematode eggs at 48.6%, 35.0%, and 14.4%, respectively; 7 species of adult FZT were recovered from these hosts. These results, combined with data from previous investigations in this community, imply that domestic animals serve as reservoir hosts for FZT and therefore must be included in any control programs to prevent FZT infection in humans.
In Asia, fi sh-borne zoonotic trematodes (FZT), including liver and intestinal fl ukes, are widely reported (1-3). FZT not only pose risks to food safety and human health but also may cause substantial economic losses in the aquaculture industry, resulting from to restrictions on exports and reduced consumer demand because of food safety concerns (4). A range of mammals and birds serve as defi nitive hosts for FZT (2). Although information on infection levels and species distribution in humans and fi sh is becoming increasingly available, similar information for reservoir hosts such as wild and domestic animals and fi sh-eating birds is scarce (1).Recent studies conducted in Nghe An Province, a major area for freshwater aquaculture in Vietnam, found prevalence of FZT in humans to be low (0.6%) and prevalence in fi sh from farms to be high (>35%) (5,6). These fi ndings suggest that reservoir hosts other than humans play a major role in sustaining transmission of FZT in this community. We therefore investigated the role of the domestic animals on these fi sh farms. We determined prevalence and species composition of FZT infections in dogs, cats, and pigs in the community and analyzed potential risk factors for the transmission of FZT to animals and animals' role in sustaining FZT infections in cultured fi sh.
Materials and Methods
Study Design, Sampling, and Laboratory AnalysisThe study was conducted in November 2005 in Nghe An Province, northern Vietnam (Figure 1), in fi sh-farming households previously investigated for human and fi sh FZT infections (5,6). From a total of 1,281 households, 50 were randomly selected in proportion to farm numbers in 5 districts: Hung Nguyen (n = 8), Nam Dan (n = 15), Yen Thanh (n = 9), Thanh Chuong (n = 10), and Tan Ky (n = 8). Another fi sh farm previously found to have cases of FZT in humans (5) was included, yielding a total of 51 fi sh-farming households in the study.