Comparative Evaluation of Pathological Lesions in Fish Collected from Different Effluent Sites in Lake Batu and Lake Hawassa, Ethiopia

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Addis Abeba University


A cross sectional study was conducted from November 2022 to May 2023 with the objective of comparatively evaluating gross and microscopicl lesions in fish collected from different effluent sites that were identified based on water chemical analysis in lake batu and lake hawassa. Water and fish samples were collected from effluent and reference sites. Mean (±SD) of water quality parameters were statistical different for a mmonia, nitrate, nitrite, silica, total dissolved solute (TDS) and alkalinity by sampling sites (P < 0.05). Mean for ammonia, nitrite, silica and alkalinity were found significantly higher (P<0.05) in Lake Batu water samples compared to Lake Hawassa. Means of all analysed water quality parameters were found significantly higher (P < 0.05) in effluent site of Lake Batu compared to reference sites. Similarly, except nitrite the mean water quality parameters were found significantly higher (P < 0.05) in effulent site compared to reference site for Lake Hawassa. Based on logistic regression analysis (OR) fish collected from lake Batu were 2.46 times more likely to develop gross gill lesions (P<0.05) ; and 1.8 times likely to develop gross skin lesions (P<0.05) than fish collected from lake Hawassa. Regarding sites of fish collection, fishes collected from effulent sites were 2.95 times mor likely to develop gross gill lesions (P<0.05); 4.67 times more likely to develop gross liver lesions (P<0.05) and 2.98 times more likely to develop gross skin lesions (P<0.05) compared to reference site in lakee Batu. For Lake Hawassa; fish collected from effulent site were 2.9 times more likely to develop gross gill lesions and 2.98 times more likely to develop gross skin lesions (P<0.05) in effulent sites compared to reference site. Based on microscopic lesions grading; la mellar necrosis for gill, multifocal hepatocelular necrosis and biliary epithelium necro sis for liver, and epidermal cell necrosis for skin were stage III lesions. Stage III lesions were identified more frequent for lake batu effulent site than lake hawassa effulent site and stage III lesions were nor identified for reference sites of both lakes. Based on microscopic lesions, haemorrhage, aneurysm and lamellar fusion in gill; aneurysm and hydropic degeneration in liver; haemorrhage, aneurism and separation of layers in skin, were stage II lesions. Stage II lesions were frequently identified in fish collected from effulent sites of both lakes and less frequent in reference sites of both lakes. Stage I lesions were lymphocytic infiltration, hyperplastic primary and secondary lamellae and goblet cell hyperplasia in gill; lymphocytic infiltration in liver; lymphocytic infiltration in skin. Stage I lesions were found in both reference and effluent sites of both lakes. It could be summarized that severe necrotic lesions (stage III) and degenerative and hemorrhagic lesion (stage II) swere more ferquent in fish collected from effulenet site than refrence site and this was also in parelell to chemical parameters of water quality. It could be concluded that the majority of stage III & stage II lesions were probably induced by contamination of lake waters by town sewerage, agricultural and industrial wastes. It also looks that lake Batu is more contaminated than lake Hawassa (based on lesion stages & water quality parameters), however, this need further detailed study. We think the result can be basics for further study and we recommend more detailed study.