Pathological investigation of fish species presenting with epizootic Ulcerative Syndrome (EUS) in Zambezi basin in Sesheke District of Zambia

Objective: 1. To isolate, confirm and document the presence of Aphanomyces invadans (EUS)in fish samples collected from Sesheke District 2.To identify fish species which are susceptible to EUS 3. To enhance EUS diagnosis through histopathology and microbiology 4. To compare the lesions in fish infected in the wild to those that may be observed in the laboratory Method & Materials: This study investigated the pathological changes that occur in fish species presenting with Epizootic Ulcerative Syndrome in the Zambezi River Basin in Sesheke' District of Zambia. Samples were also cultured for isolation of the pathogen, Aphanomyces invadans, so as to conduct biotoxicity assays and hence fulfill Koch’s postulates. A total of 270 fish were collected from the seven (7) major fishing camps in Sesheke district A purposive (biased) sampling design was employed, where the selection parameter was the lesion on the fish. The fish sampled were analysed for the presence of mycotic granulomas by histopathology Results & Conclusion: The lesions shown in fish from the wild were those of varying sizes of ulceration on the skin. Of the 270 samples collected, Clarias gariepinus was the most abundant, accounting for 20.37 per cent. Brycinus lateralis, Micralestes acutidens and Hyrocinus vittatus, on the other hand, accounted for the least numbers, at only 2.22 percent of the sample size. 57.78 per cent of the whole catch showed lesions grossly. The highest infection rates were observed in C. gariepinus. Histopathology of the positive fish species showed extensive necrotising granulomatous dermatitis. Early stages showed erythomatous dermatitis of the operculum and the caudal peduncle.

کلیدواژه ها:

Fish ، EUS ، mycotic granulomas ، Zammbezi River