Isolation and characterisation of potential bacterialpathogens from Oreochromis niloticus (Linnaeus, 1758) of Lake Hawassa, Ethiopia

Abstract

 The aim of the current study was to isolate and identify potential bacterial pathogens from Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) in Lake Hawassa, Ethiopia. The study was conducted during January to December 2021. A total of 360 Nile tilapia were sampledfrom Lake Hawassa and subjected to bacteriological investigations. The results showed 64.2% prevalence of bacterial infection in Nile tilapia from the lake. Potential bacterial pathogens such as Aeromonas hydrophila, Escherichia coli, Edwardsiella tarda, Vibrio sp,,Bacillus sp., Staphylococcus sp., Salmonella sp., Flavobacterum sp., Pseudomonas sp. and Shigella sp. were isolated. The prevalence of infection in female fish (52.4%) was higher compared to male fish (47.6%). Comparatively higher prevalence was recorded in thesmaller fish group than in the larger ones. The average bacterial loads recorded in various organs such as intestine, skin, gill, liver and kidney were, 4.86±0.56 x 105, 4.72±0.48 x 105, 4.14±0.53 x 105, 3.45±0.23 x 105 and 2.63±0.324 x 105 CFU ml-1 respectively. Significantly high bacterial loads were recorded from the intestine (5.81±0.01 x 105 CFU ml-1) of fishduring the summer season (p<0.05). The results of the study indicated that there is a risk of occurrence of disease outbreak under stressful situations. Moreover, the recovery of these bacteria in the fish which are potentially pathogenic to humans, suggests that if the fish are improperly handled, undercooked or consumed raw, may cause diseases to susceptible individuals.  Keywords:Bacterial pathogens, Lake Hawassa, Oriochromis niloticus, Prevalence