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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

Sampling fish by using cast net.Shown a throw of cast net when sampling fish from a grow-out pond in Nam Dinh.
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pntd-0000742-g002: Sampling fish by using cast net.Shown a throw of cast net when sampling fish from a grow-out pond in Nam Dinh.

Mentions: Nam Dinh province is well- known as an FZT endemic province with high FZT prevalences in humans (64.9%), cats (70.2%) and dogs (56.9%) [8], [9]. The study was conducted in Nghia Lac and Nghia Phu communes in Nam Dinh province, which is located in the Red River Delta in Northern Vietnam (Figure 2). The main stocking season is late Spring and beginning of summer. During other times of the year, juveniles are stocked at convenience by farmers. The stocked juveniles mainly originate from local nurseries. The main species stocked are grass carp (Ctenopharyngodon idellus), silver carp (Hypophthalmichthys molitrix), common carp (Cyprinus carpio), Rohu (Labeo rohita), and Mrigal (Cirrhinus mrigala). So-called self-recruiting species of fish (SRS fish) are occasionally accidently introduced to the ponds during intake of water from nearby canals. Depending on species, the stocked fingerlings are grown for 8 to 12 months to reach harvest size.


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)

Sampling fish by using cast net.Shown a throw of cast net when sampling fish from a grow-out pond in Nam Dinh.
© Copyright Policy
Related In: Results  -  Collection

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

pntd-0000742-g002: Sampling fish by using cast net.Shown a throw of cast net when sampling fish from a grow-out pond in Nam Dinh.
Mentions: Nam Dinh province is well- known as an FZT endemic province with high FZT prevalences in humans (64.9%), cats (70.2%) and dogs (56.9%) [8], [9]. The study was conducted in Nghia Lac and Nghia Phu communes in Nam Dinh province, which is located in the Red River Delta in Northern Vietnam (Figure 2). The main stocking season is late Spring and beginning of summer. During other times of the year, juveniles are stocked at convenience by farmers. The stocked juveniles mainly originate from local nurseries. The main species stocked are grass carp (Ctenopharyngodon idellus), silver carp (Hypophthalmichthys molitrix), common carp (Cyprinus carpio), Rohu (Labeo rohita), and Mrigal (Cirrhinus mrigala). So-called self-recruiting species of fish (SRS fish) are occasionally accidently introduced to the ponds during intake of water from nearby canals. Depending on species, the stocked fingerlings are grown for 8 to 12 months to reach harvest size.

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