Cross-sectional parasitological survey for helminth infections among fish farmers in Nghe An province, Vietnam.

A total of 964 adult fish farmers in five eastern districts in Nghe An province, Vietnam were investigated in late 2004 for food-borne trematodes and other helminth infections using duplicate Kato-Katz thick smears prepared from single stool samples. Eggs of fish-borne trematodes and of Fasciolopsis buski were found in 0.6 and 0.7% of farmers, respectively. Infection prevalences with soil-transmitted helminths (STHs), namely Ascaris lumbricoides, Trichuris trichiura and hookworm, were 34.8, 50.7 and 51.3%, respectively, and 81.8% were infected with at least one of the three STHs. While A. lumbricoides and T. trichiura were more prevalent in the eastern districts compared to the more western districts, the opposite was true for hookworm infections. The widespread prevalence of STH infections in fish farmers suggests that control of these infections in school-age children only may be inadequate. Identification of the human behavioural factors and environmental features responsible for the distribution and frequency of STHs among adults is needed as well as a sensitive diagnostic test of fish-borne trematodes at species level.