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Farm-level risk factors for fish-borne zoonotic trematode infection in integrated small-scale fish farms in northern Vietnam.

Phan VT, Ersbøll AK, Nguyen KV, Madsen H, Dalsgaard A - PLoS Negl Trop Dis (2010)

Bottom Line: 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.Results also highlight that the young fish are already highly infected when stocked into the grow-out systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Large Animal Sciences, Section of Veterinary Epidemiology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark. phanvan@ria1.org

ABSTRACT

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.

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Related in: MedlinePlus

A grow-out pond in Nam Dinh province.Shown a typical grow-out pond in Nam Dinh province. The pond is earthen pond and located near the households.
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pntd-0000742-g001: A grow-out pond in Nam Dinh province.Shown a typical grow-out pond in Nam Dinh province. The pond is earthen pond and located near the households.

Mentions: In Nam Dinh province in particular, is mainly practiced as small-scale family-based systems. The cultured fish are a main protein source for the households and consumed by the families at any time of the year. In Nam Dinh province, as in many other areas in Northern Vietnam, freshwater fish ponds are stocked with multiple fish species and raised in a continuous production cycle. The aquaculture activities are often integrated with livestock, and vegetable production. The grow-out ponds are earthen ponds and often located in backyard of households (Figure 1.). These systems are conducive for the life cycle of FZT as contamination with FZT eggs from animal and human hosts is high and the snail intermediate host are often present in high numbers. There have been a number of educational campaigns to stop people in Nam Dinh province from eating raw or inadequate cooked fish, however, the FZT prevalence in humans in Nam Dinh remains high [8]. It is an arduous task to convince people to stop eating raw and inadequate cooked fish because there is a long tradition for eating such dishes. Therefore, producing fish free of FZT for human consumption is important to prevent such infection in human.


Farm-level risk factors for fish-borne zoonotic trematode infection in integrated small-scale fish farms in northern Vietnam.

Phan VT, Ersbøll AK, Nguyen KV, Madsen H, Dalsgaard A - PLoS Negl Trop Dis (2010)

A grow-out pond in Nam Dinh province.Shown a typical grow-out pond in Nam Dinh province. The pond is earthen pond and located near the households.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2903470&req=5

pntd-0000742-g001: A grow-out pond in Nam Dinh province.Shown a typical grow-out pond in Nam Dinh province. The pond is earthen pond and located near the households.
Mentions: In Nam Dinh province in particular, is mainly practiced as small-scale family-based systems. The cultured fish are a main protein source for the households and consumed by the families at any time of the year. In Nam Dinh province, as in many other areas in Northern Vietnam, freshwater fish ponds are stocked with multiple fish species and raised in a continuous production cycle. The aquaculture activities are often integrated with livestock, and vegetable production. The grow-out ponds are earthen ponds and often located in backyard of households (Figure 1.). These systems are conducive for the life cycle of FZT as contamination with FZT eggs from animal and human hosts is high and the snail intermediate host are often present in high numbers. There have been a number of educational campaigns to stop people in Nam Dinh province from eating raw or inadequate cooked fish, however, the FZT prevalence in humans in Nam Dinh remains high [8]. It is an arduous task to convince people to stop eating raw and inadequate cooked fish because there is a long tradition for eating such dishes. Therefore, producing fish free of FZT for human consumption is important to prevent such infection in human.

Bottom Line: 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.Results also highlight that the young fish are already highly infected when stocked into the grow-out systems.

View Article: PubMed Central - PubMed

Affiliation: Department of Large Animal Sciences, Section of Veterinary Epidemiology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark. phanvan@ria1.org

ABSTRACT

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.

Show MeSH
Related in: MedlinePlus