Infection status of zoonotic trematode metacercariae in Sutchi catfish (Pangasianodon hypophthalmus) in Vietnam: Associations with season, management and host age

The occurrence of four species of potentially zoonotic trematode metacercariae in Sutchi catfish Pangasianodon hypophthalmus from four provinces in the Mekong Delta of the Southern Vietnam is reported. A total of 1127 fish were collected from pond cultures comprising farm house systems (FHS) (279) and from farm household systems (FHHS) (848) and examined by classical and molecular methods. The trematode metacercariae Haplorchis pumilio, H. taichui, Centrocestus formosanus and Procerovum sp. were detected and the infections were analysed in relation to season, farm management type, host size and infection site in the host tissue. Generally, prevalences in the fish were higher during the rainy season from April to October when compared to the dry season. The infection rates and densities were lower in fishes from FHHS than from FHS. Fish at an age of 61 to 90 days post-hatch showed the highest parasite loads reflecting the presence of a continuous infection risk in the ponds following stocking. The parasites were found in the body musculature, head, fins and especially at the base of fins. The importance of Sutchi catfish farming is increasing both at the local and international markets and management practices in farms and industrial processing may reduce the infection levels and thereby improve the food hygienic standard of the products.