Isolation, Identification, and Pathogenicity of Pathogens from Litopenaeus vannamei With Acute Hepatopancreatic Necrosis Disease.

Acute hepatopancreatic necrosis disease, which can cause 100% mortality, is one of the main threats to farming Litopenaeus vannamei. We identified seven strains of pathogenic bacteria from ponds with outbreaks of acute hepatopancreatic necrosis at a L. vannamei farm in Zhuhai, China. Among the seven bacteria strains, one strain was isolated from aquaculture water, two strains were isolated from hepatopancreas, and the other four strains were isolated from juvenile shrimp. The results of 16S rRNA sequencing and biochemical identification showed that all seven pathogenic bacteria were Vibrio parahaemolyticus and that they carried the pirA and pirB virulence genes. These bacteria showed ß-hemolysis with translucent rings, and six serotypes were identified. The regression infection results showed that the lethal rates of the three V. parahaemolyticus strains of serotypes O1:KUT and OUT:KUT to L. vannamei were significantly higher than those of the other serotypes. The three V. parahaemolyticus strains had the same growth characteristics, and they all entered the growth plateau at 4 h after inoculation. In addition, the pathogenicity of the three V. parahaemolyticus strains were similar. In the present study, V. parahaemolyticus was identified as one of the pathogenic bacteria causing acute hepatopancreatic necrosis of L. vannamei, and the O1:KUT and OUT:KUT serotypes may be the main pathogenic strains in Zhuhai. These results provided a foundation for the isolation, identification, and pathogenicity study of acute hepatopancreatic necrosis of L. vannamei, providing a reference for the prevention and control direction of L. vannamei disease. [ABSTRACT FROM AUTHOR]