Farm-Level Risk Factors for Fish-Borne Zoonotic Trematode Infection in Integrated Small-Scale Fish Farms in Northern Vietnam

BACKGROUND: Northern Vietnam is an endemic region for fish-borne zoonotic trematodes (FZT), including liver and intestinal flukes. Humans acquire the FZT infection by eating raw or inadequately cooked fish. The production of FZT-free fish in aquaculture is a key component in establishing a sustainable program to prevent and control the FZT transmission to humans. Interventions in aquaculture should be based on knowledge of the main risk factors associated with FZT transmission. METHODOLOGY/PRINCIPAL FINDINGS: A longitudinal study was carried out from June 2006 to May 2007 in Nam Dinh province, Red River Delta to investigate the development and risk factors of FZT infections in freshwater cultured fish. A total of 3820 fish were sampled six times at two-month intervals from 96 fish farms. Logistic analysis with repeated measurements was used to evaluate potential risk factors based on information collected through questionnaire interviews with 61 fish farm owners. The results showed that the FZT infections significantly increased from first sampling in June to July 2006 (65%) to sixth sampling in April to May, 2007 (76%). The liver fluke, Clonorchis sinensis and different zoonotic intestinal flukes including Haplochis pumilio, H. taichui, H. yokogawai, Centrocestus formosanus and Procerovum varium were found in sampled fish. Duration of fish cultured (sampling times), mebendazole drug self-medication of household members, presence of snails in the pond, and feeding fish with green vegetation collected outside fish farms all had a significant effect on the development of FZT prevalence in the fish. CONCLUSIONS/SIGNIFICANCE: The FZT prevalence in fish increased by 11 percentage points during a one-year culture period and the risk factors for the development of infection were identified. Results also highlight that the young fish are already highly infected when stocked into the grow-out systems. This knowledge should be incorporated into control programs of FZT transmission in integrated small-scale aquaculture nursery and grow-out systems in Vietnam

Heterophyes nocens Onji & Nishio, 1916 (Digenea: Heterophyidae) from the water rat, Hydromys chrysogaster Geoffroy, 1804 in Australia

A Heterophyes species from the small intestine of the water rat, Hydromys chrysogaster, in Australia is described in detail. The specimens are assigned to H. nocens, a species which many authors believed to be a synonym of H. heterophyes. From this study, H. nocens is considered a valid species as it differs from H. heterophyes in the number of sclerites on the gonotyl, the course of the uterus, coefficients of allometric growth of the suckers and the presence of genital sinus spines

Genetic differences among Vietnamese<i>Haplorchis taichui</i>populations using the COI genetic marker

AbstractAdults of the fish-borne intestinal trematode speciesHaplorchis taichuiwere collected from humans in three provinces of Vietnam: Ha Giang, Thanh Hoa and Quang Tri. Genetic analysis revealed three groups of the parasite from clustering dendrograms, correlating with the localities in which they were collected. Measurements of evolutionary divergence over sequence pairs were greater between the different populations than within them, which indicated that the three populations were genetically different. The significance (Fst= 0.73;Pvalue &lt; 0.05) of the genetic variation of the three studied populations implied that genetic separation of the populations had already occurred, which may have been caused by a low gene flow among the differentH. taichuipopulations. Factors contributing to the low gene flow may include isolation resulting from the intermediate-host fish rarely being sold outside of the rural commune where they are raised and the enclosed aquacultural areas themselves.</jats:p

Recovery of Cyclospora cayetanensis among asymptomatic rural Thai schoolchildren

AbstractObjectiveTo obtain the prevalence with clinical symptoms of Cyclospora cayetanensis (C. cayetanensis), a coccidian protozoan parasite, in Thailand which is the cause of an intestinal infection characterized by sporadic-to-frequent explosive diarrhea.MethodsIn a field survey conducted by the Faculty of Tropical Medicine, Mahidol University, as part of the existing parasite-control program, a total of 2 540 faecal samples from villagers in Nan Province, Thailand, were collected and examined to determine the prevalence and clinical characteristics of parasitic infections.ResultsTwelve cases of C. cayetanensis infection were found during faecal examination of schoolchildren aged 5-12 years. None exhibited obvious clinical symptoms, especially evidence of diarrhea; 5 of 12 had loose faeces, one reported frequent symptoms of abdominal discomfort, and another had pale conjunctiva with low hematocrit. The children were generally asymptomatic.ConclusionsThis finding confirms a public-health issue with potentially serious consequences whereby children can be exposed to an environment contaminated with food-and water-borne transmitted oocysts, and can hence become infected with C. cayetanensis