Outbreak of a novel disease associated with Vibrio mimicus infection in fresh water cultured yellow catfish, Pelteobagrus fulvidraco

• The manuscript reported a novel bacterial disease in cultured yellow catfish.
• It described for the first report that Vibrio mimicus can infect fresh water fish.
• MLSA was confirmed to be robust way to distinguish V. mimicus from V. cholerae.

An outbreak of a novel disease characterized by serious and regularly shaped ulcers in the skin was recorded in cultured yellow catfish (Pelteobagrus fulvidraco) in Guangdong and Guangxi provinces of South-China in 2011. Several bacterial strains that exhibited the same phenotypic traits and biochemical characteristics were isolated from the lesions of diseased fish. One bacterial isolate named XQ was identified as Vibrio mimicus according to biochemical tests and phylogenetic analysis derived from 16S rDNA, rpoA, recA and pyrH gene sequencing. In challenge trials, the bacterial isolate XQ exhibited high virulence in yellow catfish with an intra-peritoneal LD50 value of 3.39 × 106 CFU per fish. In addition, skin ulcers occurred in all challenged fish groups whether they were treated with the bacterial isolate XQ by intraperitoneal injection, oral delivery or bath exposure, suggesting that the V. mimicus is the etiological agent of the enzootic and could infect the host fish via more than one route. Furthermore, histopathology of diseased fish infected with V. mimicus showed destruction of the epidermis and fibrinoid necrosis in skin; renal tubular epithelial cell necrosis in kidney; hepatocyte swelling and serious hemorrhage in the liver; macrophage aggregations and necrosis of the lymphoid tissue in spleen; severe necrosis and shedding of the intestinal mucosal villi in intestines; and, edema and exfoliation of epithelial cells in gill secondary lamellae.