Study on parasitic helminths infecting three fish species from Koka reservoir, Ethiopia

Abstract

A cross-sectional study was conducted in three species of fish from Koka reservoir from November 2008 - April 2009 to determine the prevalence of helminth parasites and identify the most common genera infecting fish. A total of 315 fish comprising of 97 (30.8%) Barbus intermedius, 145 (46.0%) African catfish (Clarias gariepinus), and 73 (23.2%) Nile tilapia (Oreochromis niloticus) were caught by gill nets of variable sizes and long line hook. All the sampled fish were examined externally and internally for the presence of helminth parasites. Of all fish examined, 209 (66.3%) were found to harbour either single or multiple species of helminth parasites. A significantly higher (P<0.05) infection was found in C. gariepinus than other fish species. There was no significant variation (P>0.05) between B. intermedius and O. niloticus. There was no significant (P>0.05) relationship between infections and size (body length) categories. The study demonstrated that Contracecum species from mesentery and pericardial cavity was most prevalent nematode (24.8%) in C. gariepinus followed by 16.5% in B. intermedius and 5.4% in O. niloticus. Gyrodactylus species was the only monogenean detected from the fins of B. intermedius. Clinostomum species from branchial and pericardial cavities was the dominant digenean with high prevalence in O. niloticus (27.4%). The highest prevalence (77.9%) of Diplostomum species was recorded in C. gariepinus from cranial cavity followed by unidentified cestodes (35.9%) detected from the mesentery and body cavity. Proteocephalus species was detected in 11.34% of B. intermedius from intestine and body cavity. This work revealed that helminth parasites are widespread in fish from Koka reservoir and C. gariepinus was particularly the most highly infected fish than B. intermedius and O. niloticus. The study cautions the development efforts when stocking of community aquaculture facilities and artificial reservoirs as part of the food security programme.