Freshwater Aquaculture Nurseries and Infection of Fish with Zoonotic Trematodes, Vietnam

Van Thi Phan,Khue Viet Nguyen,Thanh Thi Nguyen,Anders Dalsgaard,Ha Thi Nguyen,Annette Kjær Ersbøll,Darwin Murrell

doi:10.3201/eid1612.100422

Abstract

Residents of the Red River Delta region of northern Vietnam have a long tradition of eating raw fish. Fish-borne zoonotic trematodes (FZTs) are estimated to infect ≈1 million persons in Vietnam. It remains uncertain at what stages in the aquaculture production cycle fish become infected with FZTs. Newly hatched fish (fry) from 8 hatcheries and juveniles from 27 nurseries were therefore examined for FZT infection. No FZTs were found in fry from hatcheries. In nurseries, FZT prevalence in juveniles was 14.1%, 48.6%, and 57.8% after 1 week, 4 weeks, and when overwintered in ponds, respectively. FZT prevalence was higher in grass carp (p<0.001) than in other carp species. Results show that nurseries are hot spots for FZT infections in fish. Thus, sustainable FZT prevention strategies must address aquaculture management practices, particularly in nurseries, to minimize the risk of distributing infected juveniles to grow-out ponds and, subsequently, to markets for human consumption.

Highlights

Residents of the Red River Delta region of northern Vietnam have a long tradition of eating raw fish
Liver and intestinal infections caused by fish-borne zoonotic trematodes (FZTs) are increasingly being recognized as serious public health problems and with Fish-borne zoonotic trematodes (FZTs) incorporated among causes of neglected tropical diseases [1,2]
We report an investigation that aimed to determine the FZT infection status in integrated small-scale hatcheries and nurseries in Nam Dinh, Ninh Binh, and Bac Ninh provinces, which are major areas endemic for FZTs in Vietnam

Summary

Introduction

Residents of the Red River Delta region of northern Vietnam have a long tradition of eating raw fish. Fish-borne zoonotic trematodes (FZTs) are estimated to infect ≈1 million persons in Vietnam It remains uncertain at what stages in the aquaculture production cycle fish become infected with FZTs. Newly hatched fish (fry) from 8 hatcheries and juveniles from 27 nurseries were examined for FZT infection. The epidemiology of FZTs is complex because humans and reservoir hosts, such as dogs, cats, pigs, and fish-eating birds, harbor egg-shedding adult stages [12,13] These hosts are infected by consumption of raw, inadequately cooked, or pickled fish. In the Nam Dinh and Ninh Binh provinces, the widespread habit of eating raw fish is associated with a high FZT prevalence of 30%–40% in humans [3,4]. The water reservoirs are cement tanks or consist of earthen ponds from which the water is either pumped into cement breeding tanks or supplied from a tower to the breeding

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Results

Conclusion