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. |
