Non-Vibrio Parahaemolyticus Causing Acute Hepatopancreatic Necrosis on Brackish Shrimps

Abstract

   Acute hepatopancreatic necrosis disease (AHPND), also known as Early Mortality Syndrome (EMS), has become one of the most harmful threats to the shrimp aquaculture industry in Southeast Asia, including Vietnam. It occurs on both tiger and white leg shrimps at 20 - 45 days of age with a mortality rate up to 100%. AHPND pathogens were identified as bacteria containing plasmid carrying toxin genes that cause acute hepatopancreatic necrosis. Observation of biochemical characteristics, the use of PCR technique using specific primers to detect the toxin genes and sequence analysis of 16S-rRNA gene confirmed that there were at least three strains of AHPND pathogenic bacteria on brackish shrimp cultured in Vietnam, of which two strains belong to Vibrio parahaemolyticus species, including V. parahaemolyticus KC13.14.2 and V. parahaemolyticus KC12.020; and the other strain of Vibrio sp. KC13.17.5. Vibrio sp. KC13.17.5 was confirmed as V. harveyi KC13.17.5, a non V. parahaemolyticus species. The detection of non - V. parahaemolyticus that caused AHPND is a new finding not only in Vietnam but also worldwide.