The aim of this study was to investigate the infection of RedSwamp crayfish, Procambarus clarkii with  Flavobacterium columnare and the role of crayfish for transmission of columnaris disease to wild sharptooth catfish, Clarias gariepinus, 100 crayfish were subject to clinical, postmortem and bacteriological examinations. Pathogenicity of Flavobacterium columnare was also assessed to sharptooth catfish. Out of 100 apparently health crayfish, F. columnare was isolated from only 15 (15%) crayfish. Bacteria identification was based on colony morphology and culture behavior on cytophaga agar, microscopic examination, biochemical tests and carbohydrate fermentation. Strains F. columnaris isolated from gills of infected crayfish were used throughout this study.  Pathogenicity of Flavobacterium columnare was investigated through an immersion challenge. CatFish groups to be challenged were subjected to skin and/or gill scarification, others remained un-scarified. All challenged fish were immersed in 2.1x10⁶ colony forming unit/ml of F. columnare challenge suspension. Clinical signs on challenged fish were restricted to the external surface, erosion, ulceration until reach to complete loss of skin, pale gills. The mortality rate in skin and gill scarification group, skin with scarification group, gills scarification was 100%, 80%, 60% respectively, whereas, mortality rate in immersion-without scarification group was only 10%. The antibiogram of F. columnare was also investigated where it was sensitive to oxytetracycline, oxalinic acid and erythromycin but resistant to tobramycin, amoxicillin, sulfamethazole, polymixin B and neomycin.