pathological studies on protozoal infection in some freshwater fishes

Three fresh water fishes (tilapia, catfish and common carp) were collected from Abbassa Farm, branches of the river Nile and private fish farms in Sharkia Governorate during the period from January, 2008 to December, 2008 to investigate their external andThis study revealed that 141 (16.53%) out-of 853 fishes were infected with different protozoan parasites. The infection-rate was, 62.41% in catfish, 29.78% in tilapia and 7.81% in common carp. Concerning the seasonal variations, it was found that the highTrichodina infected the gills and skin where it led to desquamation of the epithelial covering of the gill-filaments and sloughing of the epidermis. Moreover, hyperplasia and hypertrophy of the secondary lamellar epithelial covering led to .