The present study was carried out as a general survey searching for the possible protozoan parasites that can infect the Nile fish Oreochromis (Syn: Tilapia) niloticus. A total of 217 live fish specimens were obtained from the River Nile at Giza district (Pharaonic Village, Imbaba and El-Warak). Examination of the investigated fish species in this study
revealed that fishes are infected with numerous protozoan parasites which have pathological effects on the host fish with subsequent economic losses. 15 different species belonging to 6 genera of parasitic protozoa were detected. Identification of parasites, their incidence, and intensity of infection were discussed. Generally, the detected protozoan parasites were classified into three main categories: 1- Ectoparasites: Under which 5 different species were detected.
2- Myxosporea: Under which 3 species of the genus Myxobolus were detected.
3- Coccidia: Under which 7 different species were recorded: three of Isospora; two of Eimeria and two coccidian oocysts of
unidentified species. Among the obtained parasites, the following were recovered for the first time from O.niloticus in Egypt, Myxobolus sp1. Myxobolus sp3. Isospora sp1.
Isospora sp2. Isospora sp3. Eimeria sp1., Eimeria sp2. and the two
unidentified species of coccidian