Studies on Some Parasitic Diseases in Oreochromis niloticus Fish Hatchery with Emphasis to Life Stages

This study was conducted on 210 Oreochromis niloticus (O. niloticus) of different life stages including (100 fry, 100 fingerlings and 10 broodstocks) obtained from a private fish hatchery at Kafer El-Sheikh Governorate, Egypt; during August 2014. The hatchery complains 30% mortality among fry and fingerlings while no mortalities was recorded among broodstocks. Parasitological examination revealed heavy infestation with Triochodina species (sp.) in all examined life stages at a prevalence rate 100%. In addition, Gyrodactylus sp. was recorded in gills of fry, fingerlings and broodstocks at a rate of 5, 12, and 10 %, respectively. Kidneys and gills of all examined life stages showed heavy infestations with Myxosporean sp., with 100 % prevalence rate. Haemogregarina sp. was described in the blood of fingerlings and gill tissues of broodstocks. Additionally, Encysted metacerceria was observed in gills of broodstocks. The recovered parasites were demonstrated hisopathologically in the gill and kidney tissues of the examined fish. The histopathological examination revealed that the infested gills exhibited serious lesions such as hyperplasia and hypertrophy of the lining epithelial cells of the gill filaments, fusion and necrosis of secondary lamellae and vasodilatation. The lining epithelium of the renal tubules showed degenerative and necrotic changes with the presence of various developmental stages of myxosporidia. In conclusion, fry and fingerlings exhibited high mortalities, while no mortality was recorded among broodstocks, regardless the intensity of infestation and severity of pathological alterations which was intense in broodstocks.