Studies of Pathological Changes in Tilapia Species Due to Motile Aeromonads Infection

Abstract

The present study was carried out to throw a light on the most common septicaemic diseases in Egypt, Motile Aeromonad Septicaemia (M.A.S.) is the most important one of them, 200 Tilapia Spp. showed different external septicaemic lesions and collected from central laboratory for aquaculture research at Abassa, Sharkia governorate, Egypt during the period of fish catching (Febmary to April 1995). The bacteriological examination successed to isolate local strain of A.hydrophila. The isolated local strain studied regarding the vimlence factors and pathogenesis which required experimental infection and collection of samples at different times. The samples studied bacteriologically, histopathologically and by electron microscope.

The experimental infection of fish occured via two routes, Abrasion of the skin (NS) and Intragastric (Vg). The results of this study revealed the ability of the isolated local strain to produce different types of vimlence factors including haemolysin, haemagglutenin and enterotoxins while the protease enzyme production suggested by the results of electron microscopy where the micro-organism caused zone of cytoplasmic lysis in the macrophage cells.'!--

Pathological changes in case of natural infection:-

The postmortem examination of naturally infected fish revealed 2 forms of infection either cutaneous form or systemic form. The presence of 2 forms confirmed by histo pathological studies where sometimes the