First report on parasitic infections of Pangasius macronema in Can Tho City, Vietnam

The study aimed to evaluated parasite infections of Pangasius macronema from January to December 2023. A total of 200 samples (including 100 farmed and 100 wild Pangasius macronema) were randomly collected from Can Tho city, Viet Nam. Samples were examined for clinical signs and fresh smears were prepared for parasite examination. Most of the analyzed fish were healthy, without any clinical signs. However, some exhibited distended abdomens and white spots on the liver. The results revealed eight parasite genera in P. macronema, including: Apiosoma sp., Myxobolus cysts, Dactylogyrus sp., Epistylis sp., Ichthyonyctus sp., Metacercariae of digenetic trematodes, Protoopalina sp. and Trichodina sp. Six genera were found on the gills and three in the intestine and liver. The composition, intensity and prevalence of parasites were generally higher in wild P. macronema compared to cultured P. macronema. In wild fish, Trichodina sp. had the highest prevalence, infecting 66.0% of gills with an intensity of 1-27 parasite fish-1, while Myxobolus cysts had the lowest prevalence of 16.0% in the liver with an intensity of 1-6 cysts per fish. In cultured fish, Trichodina sp. also had the highest prevalence, infecting 47.0% of gills with an intensity of 2-19 parasite fish-1 and Dactylogyrus sp. had the lowest prevalence of 22.0% on the gills with an intensity of 1-7 parasite fish-1. Generally, these findings reflect the relatively occurrence of parasites among the cultivated and wild P. macronema, confirming the necessary of strick measures to control the infections.