Characterization of Lesions in Diseased Fishes, Isolation and Identification of Edwardsiella Tarda from Selected Lakes and Ponds of Ethiopia |Biomedgrid

Background: Fish is a nutritious animal rich in protein and consumed than other feeds throughout the world. Although many infectious agents affect fish species, bacterial infections are the known causative agents affecting fish industries. Methods: A cross-sectional study with purposive sampling was conducted from December 2020 to May 2021 with the objectives of lesion characterization in diseased fishes, isolation, and identification of Edwardsiella tarda (E.tarda) from Batu, Langano, and Babogaya lakes and ponds in Bishoftu. Results: A total of 60 fishes were examined for this study. Skin, muscle, gill, liver, kidney, spleen, and heart were inspected grossly and collected for microscopic lesion characterization and E.tarda isolation. Out of 60 samples, 28.3% (n=17) and 25% (n=15) were positive for E.tarda by bacteriological and conventional PCR (E.tarda rest at 114bp) respectively. There was significant difference (P<0.05) observed in the frequency of identifying E.tarda between the three study areas and four fish species, but, there was no significant difference between the sex groups (P>0.05). After the histopathological process and staining, tissues were divided into two based on E.tarda confirmation. Gills from E.tarda positive fishes revealed hyperplasia, focal necrosis, and swelling of the lamellar epithelium. Microscopic lesions in the liver include nuclear condensation, cytoplasmic vacuolation, and swelling of hepatocytes. Lesions in the hepatic blood vessels comprise severe hyperplasia of the endothelium, hyperemia, and elastic fibers in the intima of hepatic artery. Kidneys of E.tarda positive fishes had suppurative interstitial nephritis, melano-macrophage deposition in interstitium, and interstitial hemosiderin deposition. There were infiltration of inflammatory cells and focal area necrosis of the epidermis, lymphocyte infiltration in muscle, and accumulation of hemosiderin pigments in spleen. Microscopic lesions in E.tarda negative fishes indicated significant changes like lamellar epithelial degeneration with vacuolation, and total necrosis of structure in gill, periportal hepatitis, and hepato-necrosis with vacuolation of liver, glomerulitis, multifocal tubulointerstitial nephritis, epithelial cells degeneration and cloudy swelling in kidney, dermal edema in skin and myocarditis with fibrosis of heart. Conclusion: Based on the study several lesions were identified from diseased fishes. The characterized lesions show the occurrences of different diseases in fishes of selected study areas. Thus, further studies on lesion characterization in diseased fishes of different species with large sample sizes and study area should be conducted.