GaoliangYuan,LeiZhu,XinyuJiang,JieZhang,ChaoPei,XianliangZhao,LiLi,XianghuiKong
Abstract
Red swamp crayfish Procambarus clarkii is an economically important species that is widely cultivated throughout China. With the application of high-density culture, P. clarkii is usually infected by different pathogens in water. Co-infection with multiple pathogens was common, which has resulted in greater economic loss than single infections. In this study, we investigated a case of co-infected crayfish with bacterial and viral pathogens at a local farm. Firstly, a bacterial strain was isolated from the gills of infected crayfish. According to the results of 16S rRNA sequence and analysis of the Biolog Gen III MicroPlate system, the isolated bacterial strain was finally identified as Aeromonas veronii. The isolated A. veronii exhibited significant virulence to crayfish, with an LD50 value of 6.04 × 106 CFU/crayfish. As a result, drug sensitivity tests showed that the isolated A. veronii was completely resistant to ampicillin, penicillin, and compound sulfamethoxazole tablets, and highly sensitive to seven kinds of antibiotics. Furthermore, white spot syndrome virus (WSSV) was also detected from the gill tissue of diseased crayfish by polymerase chain reaction. After experimentally co-infected with A. veronii and WSSV, the healthy P. clarkii presented similar clinical and histopathological signs with natural infected P. clarkii. The mortality of the co-infected group was 100%, which was higher than that in the group single infected with A. veronii (70%) or WSSV (83.3%). In summary, a case of co-infection with WSSV and A. veronii from P. clarkii was comprehensively studied in this study. The results will supply an effective diagnosis strategy for the co-infection, and provide therapy reference to prevent and control P. clarkii disease.
Keywords
Procambarus clarkii,Co-infection,White spot syndrome virus,Aeromonas veronii