Isolation and Identification of Edwardsiella tarda from Lake Zeway and Langano, Southern Oromia, Ethiopia

A study was carried out from October, 2009 to April, 2010 with the objective of isolating Edwardsiella tarda an important fish pathogen from fish harvested for human consumption from Lake Zeway and Langanoo. A total of 372 tissue samples (three from each fish) comprising liver, intestine and kidney were collected from 124 fish (Clarias gariepinus and Oreochromis niloticus originated from Lake Langanoo and Zeway. Distribution of E. tarda infection among the three organs examined indicated that E. tarda was isolated most frequently from liver (6.5%) followed by intestine (2.4%) and kidney (0.8%) with significant difference among organs. Statistical significant differences (P<0.05) were found in E. tarda infection with respect to site although the bacterium was isolated from fish originating from both Lake Zeway and Langanoo with E. tarda being more prevalent in fish sampled from lake Zeway. E. tarda was isolated more frequently from male fish, the differences in the occurrence of E. tarda infection with respect to sex were not significant (P>005) indicating that both sexes are equally susceptible. The isolation of Edwarsiella from wild fish population of Lakes Zeway and Langano destined for human consumption in the current study is indicates that E. tarda is a potential threat of both the fishery sector/aquaculture and public health. Finally, as is the case for any infectious fish pathogen, there is limited information on E. tarda of fish in Ethiopia and hence further study to have comprehensive information on the agent is forwarded.