Histopathological investigations on experimentally Edwardsiella tarda infection in zebrafish

In this study, the histopathological changes in the organ and tissues of juvenile zebra fish (one month age) experimentally infected with Edwardsiella tarda (E. tarda) were shown by using histologic technic and staining methods. For this reason, as a result of epruvation which was applied to zebra fish as intraperitoneal (ip) injection and immersion method, the infection development in the fish was provided. The histopathologic changes which were formed in the organ and tissues of the zebra fish realted to the experimental applications were made ready by using histological methods and techniques. As a result of ip injection and immersional applications via light microscopically evaluations, the lesions in the organs and tissues of the zebra fish were evaluated, were photographed and the observed microscopic findings were recorded. In microscopic examinations, in 104 - 105 (Colony Forming Units/mililiter) CFU/ml ip experimental groups the following important findings were observed: hemorrhage and fibrinous inflammation in peritonea, severe congestion in liver, vacuolization of hepatocyte, locally mononuclear cell infiltration in gills and primer lamellas and degeneration in pillar cells, diffused or local mononuclear cell infiltrations in muscular tissue, diffused degeneration and necrosis and hemorrhage areas in the muscles. Compared with other groups, in the immersion groups of 106 - 107CFU/ml, less severe congestion in livers, and vacuolization of hepatocytes, degeneration and focal necrosis areas in muscles were observed. In control group no histopathological changes were observed. As a result, related to the experimental infection of E. tarda in zebrafish, much severe lesions were formed in ip injected group while the lesions of immersion group were less severe and slight. During the study, only the death of one of the zebra fishes was observed and throughout the experiment the rare amount of death despite the observed histopathological lesions in fishes shows that zebra fish is rather resistant to the infection of E. tarda.