Experimental Histopathologic Studies of Some Septicemic Bacterial Diseases on Fresh Water Fish

The present study was carried out to study the most common septicemic disease of fish in Egypt, M.A.S. One hundred and sixty Tilapiaspp. showing different external septicemic lesions, were collected from The Central Laboratory for Aquaculture Research at Abassa, SharkiaGovemorate, during the period of fish catching (February-April 1996). Thebacteriological examinations were performed to isolate A. hyDROPhila, A.caviae and A. sobria.The pathogenesis and pathogenecity of the isolates; A. sobria and A.caviae were experimentally studied in Tilapia spp. Collected samples atdifferent times were bacteriologically investigated. The experimentalinfection of fish was accomplished via 3 routes, intraperitoneal (IP),intramuscular (IM) and per os (PO). The results of this study revealed thatthe IM route gave more severe lesions than hte other two routes. Specimenswere collected from the naturally and experimentally infected fish at periodswhich ranged from 12 hrs to 2 weeks PI. The specimens were fixed inbuffered formalin. Five micron thick paraffm sections were prepared andstained for microscopic examination.Pathological changes in case of natural infection revealed that thepost-mortem lesions of the naturally infected fish displayed 2 forms which