Seasonal variation and quantitative epidemiological indices of digenetic trematodes in Eutropiichthyes vacha inhabiting the Ganges River in Chandauli, Uttar Pradesh, India

Digenetic trematodes have a major impact on the health of freshwater fish, aquaculture, and biodiversity. The freshwater fish carry heavy infections of helminth parasites, resulting in poor growth, delayed sexual maturity and mortality of fish. Eutropiichthyes vacha is one of the common freshwater fish abundantly found in the Ganges River, Chandauli, Uttar Pradesh, India. The current study examines seasonal variation in the prevalence, mean intensity, and abundance of digenetic trematode parasites that infect the freshwater catfish Eutropiichthyes vacha, as well as the infection of digenetic trematodes, which was also recorded in relation to the length and weight of fish. A total of 120 specimens of Eutropiichthyes vacha were examined from March 2024 to February 2025. Digenetic trematodes were recovered from the intestine and pyloric caeca of infected hosts. The infection showed a mean intensity of 1.19 parasites per infected host and an abundance of 0.45, with an overall prevalence of 38.33%. Among different size classes, the highest prevalence was recorded in the 6–10 cm length group, while larger fishes exhibited lower prevalence. A similar trend was observed with respect to body weight, where lighter individuals showed greater infection prevalence compared to heavier ones. Seasonal analysis revealed that E. vacha was most susceptible to trematode infection in September.