Investigation on Vibrio harveyi bacteria association in mortality of cultured Asian seabass (Lates calcarifer) in farm located in Iran Southern provinces with culture and PCR method

Vibrio harveyi is of the bacterial flora of omnivorous fish intestine that is considered as one of the main causes of the Asian seabass (Barramundi) fish vibriosis disease in many cage farms in the world. The purpose of this study was to investigate the role of this bacterium in the mortality of Asian seabass fish in southern regions of the Iran.  In this study, in 11 cases of Asian seabass mortality, a total of 110 Asian seabass fish (80 suspected vibriosis fishes and 30 healthy fish species) from southern provinces (Khuzestan, Bushehr and Hormozgan) were sampled and bacterial culture from the internal organs was done. Biochemical and molecular characteristics (with specific primers of genus and species) of isolates were investigated. Nine (81.81%) cases of vibrios (Vibriosp). Were diagnosed as causative of mortality.  The results showed that in fish with symptoms of vibriosis, 70.76% of the isolates were V. harveyi. Also, in the seasonal study, the prevalence of V.harveyi, the losses due to vibriosis and the highest prevalence of infection with this bacterium were observed in spring. The antimicrobial susceptibility test of 46 isolates of V. harveyi isolates was also investigated. The results of this study indicate the significant role of Vibrio harveyi in the mortality caused by vibriosis in Asian seabass fish farms in Iran. The results are important for prevention perspective (health management and vaccination) and the effective treatment of Vibriosis disease in Asian seabass fish, these results are important.