Prevalence of diegenetic encysted metacercariae and their histopathological alterations in the Nile tilapia (Oreochromis niloticus), and the African catfish (Clarias gariepinus)

Parasitic infestation has a serious impact on fish health causing severe economic losses in fish farming as well as it has public health importance. This investigation was conducted on the prevalence of diagenetic encysted metacercariae (EMC) and its histopathological alterations in some freshwater fishes sampled from El – Riah El- Tawfiki, Qaliobia Governorate, Egypt. In this regard, a total of 600 randomly collected fish comprising 400 Nile tilapia (Oreochromis niloticus), and 200 African catfish (Clarias gariepinus) were examined macroscopically and microscopically from December 2020 to September 2021. The infested fishes showed white to yellowish cysts/nodules of variable size in different organs. The recorded EMC was identified microscopically as Clinstomum spp, Euclinostomum spp, Haplorichiaed spp, Pygidiopsisgeneta spp, Cyanodiplostomum spp, and Prohemistomulum spp. in the Nile tilapia and Prohestomatide spp. in African catfish. The overall prevalence of EMC was 29.25% in Nile tilapia and 22% in African catfish. The highest seasonal prevalence of EMC was 43% in summer for Nile tilapia and 34% in winter for African catfish. kidneys of Nile tilapia and musculature of African catfish recorded the highest tissue distribution of overall recorded EMC. Severe histopathological changes were observed in fish organs including gills, subcutaneous musculature, kidneys, liver, and ovaries. In conclusion, these results reflect the negative impacts of EMC on fish reproduction and general health status, therefore awareness about the control of fish parasites especially in natural resources should be conducted.