Clinical Outbreaks of Flavobacterium columnare among Tilapia Populations from Lake Qarun, Egypt

Abstract

During multiple clinical outbreaks that happened between the fall and winter of 2012. A total of 59 fish pathogenic bacteria were retrieved form 150 clinically diseased Tilapia species collected from different regions through Lake Qarun. The dermotropic yellow pigmented F. columnare have represented 3.4% of the retrieved Flavobacterial isolates. The main clinical findings exhibited by F. columnare natural infection were deep ulcerations and tail rot. The lake’s poor water quality such as alkaline pH , high levels of un-ionized ammonia, high nitrite concentrations, together with the abrupt rise of water temperature have played a potential role in triggering F. columnare infection. To assess the pathogenicity of the retrieved isolates, experimental infection was carried out by intraperitoneal injection of O. niloticus with F. columnare isolates and mortalities were detected within 10 days. F. columnare isolates were sensitive to Danofloxacin, Nalidix acid, Nitrofurantoin and Oxolinic acid while they were resistant to Amoxicillin, Cephalothin, Gentamicin, Lincomycin, Oxytetracycline, Ampicillin, Tetracycline.