Prevalence and molecular characterization of Centrocestus formosanus in wild tilapia from the Western Nile Delta of Egypt.

Centrocestus formosanus is a small, fish-borne zoonotic trematode belonging to the family Heterophyidae. It causes financial losses in the aquaculture industry. In this research, we aimed to study the prevalence of metacercariae among wild tilapia fish, histopathology, and molecular characterization of Centrocestus formosanus using ITS-2 gene PCR. The overall prevalence of C. formosanus was 72.07 %. The prevalence was 68.50 % for S. galilaeus, 74.28 % for O. niloticus, 73.64 % for T. zillii, and 78.57 % for O. aureus. The prevalence was 71.45 % in Kom Hamada City and 73.66 % in Eldelengat City. Autumn showed the highest prevalence of 75.42 %. The small-size fish had the highest prevalence of 71.71 %. Microscopically, the encysted metacercariae of Centrocestus exhibited characteristic X-shaped excretory vesicles. Severe inflammatory reactions and cartilaginous hyperplasia were observed, causing distortion and thickening of the primary lamellae. Epithelial cell hyperplasia and blood vessel hyperemia led to the gill secondary lamellae thickening. PCR of the ITS-2 gene successfully amplified specific bands. The sequences were highly identical to those from Israel, Vietnam, Singapore, Thailand, Iran, and China. Phylogenetic analysis revealed the clustering of Egyptian ITS-2 sequences with those from Israel, Thailand, Vietnam, Singapore, Iran, and China. In conclusion, this study presents the prevalence, histopathology, and first molecular characterization of Centrocestus formosanus in wild tilapia from the Western Nile Delta of Egypt.