Tropentag, October 11 - 13, 2005 in Stuttgart-Hohenheim "The Global Food & Product Chain – Dynamics, Innovations, Conflicts, Strategies"

Pathological Evaluation to Some Protozoa Infections among Freshwater Fish in Egyptian Aquaculture

¹Worldfish Centre, Fish Health, Egypt
²Zagzzig University, Parasitology, Egypt
³Central Lab for Aquaculture Research, Sharkia, Egypt

Abstract

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%), Eimeria 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. drepanopsettaeresulted 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. parvu 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

Contact Address: Salah Aly, Worldfish Centre, Fish Health, Abbassa, 44662 Abu-hammad, Egypt, e-mail: s.mesalhycgiar.org