SALAH ALY1, SADDIK FAYEK2, OMAR AMER2, AHMED EL-ASHRAM3, GEHAN SHAGAR3
1Worldfish Centre, Fish Health, Egypt
2Zagzzig University, Parasitology, Egypt
3Central Lab for Aquaculture Research, Sharkia, Egypt
1088 fish (Oreochromis niloticus, O. aureus, Tilapia zillii, Clarias gariepinus and Cyprinus carpio) were examined from Abassa farms, Egypt, for internal protozoa during 2001-2003. 67% of fish were infected with enteric protozoa. The infection rate among O. niloticus, O. aureus, T. zillii, C. gariepinus and C. carpio was 62, 57, 80, 58 and 50%, respectively. The highest infection rate was seen in spring (81%), followed by summer (72%), autumn (60%) and winter (48%).
Eimeria aurati (35.3%), E. rutili (4%), E. sp. (11%), Goussia sp. I (34.2%), G. sp. II (2.6%), Cryptosporidium nasorum (47.2%), Myxobolus nkolyaensis (2.2%), M. carassii
(2.2%), M. pharyngeus (9.2%), Mixidium lieberkuehni (1.1%), Ceratomyxia drepanosettae (1.8%), Entamoeba molae (7%), Hexamita sp. (7%) and Trypanosoma tilapiae (0.7%) were recorded. The incidence of protozoa varied with fish species.
Histopathological results: E. rutili induced tubular nephrosis with developmental stages and activation of melanomacrophages. Goussia sp. was recovered from the gas-bladder with no lesion. Myxobolus induced intestinal mucinous degeneration, melanomacrophages and leukocytes in Lamina propria. The lumen contained spores and sloughed epithelium. C. drepanopsettae induced severe enteritis with focal sloughing, the lumen contained protozoan tissue debris and leukocytes. E. molae and Hexamita infections induced mild intestinal degeneration with mononuclear and eosinophilic cells. T. tilapiae induced vascular lesions, hepato-cellular and hematopoietic alterations. Successful transmission of Cryptosporidium parvum and Balantidium coli was experimentally done from cattle to C. gariepinus. C. parvum infection induced intestinal epithelial desquamation with congestion and leukocytic infiltration. Merogony and gamogony were seen attached to intestinal brush border. With B. coli infection, trophozoites and cysts were seen in intestinal lumen with minimal mononuclears.
We concluded that protozoa infections are common among freshwater fish, especially in spring where Eimeria sp. was the most prevalent infection. The infection was high in T. zillii and low in C. carpio. Transmission of C. parvum and B. coli from mammals to fish are possible. These protozoa induced various pathological changes that could interfere with the growth and/or survival of the infected fish. Therefore, protozoa infections in fish should be controlled.
Keywords: Aquaculture, carp, catfish, Egypt, fish, freshwater, histopathology, prevalence, protozoa, season, tilapia