pathological studies on some parasitic diseases of tilapia species

Eleven hundred and eighty living Tilapia fishes of different ages werebrought living to the laboratory in nylon bags from Abbassa fish hatshery(Sharkia province) and Manzala lake (Dakahlia province) during the periodfrom 1990-1991 (different seasons of the year) to study the lesions inducedby some digenetic trematode larvae, beside their prevalence and theassociated signs. The affected Tilapia fish-skin was examined first followedby the gills, fins and eyes to look for external parasites, then the fishes werenecropsied and specimens from the muscles, eyes, spleen, liver and kidneys were fixed in neutral buffered formalin. Five to seven micron thickparaffin sections were stained with hematoxylin and eosin then examinedmicroscopically. Samples (snips)from the muscles were compressed between2 slides and microscopically examined.Six parasitic larvae (Diplosronlunl pal”aCaUdUnl, D. tilapi, Euclinostomum nephrostomum, Heterophyid ”Centrocestus armatus”.Haplorchis pumilio and Prohemistomum vivax) were identified. The familiesof the majority of such encysted parasites were identified according to the observed clinical signs, morphology (parasitic elements, sizes, shapes andcapsules) of the encystedmetacercariae, the severity of the inflammatory