AHPND has a bacterial aetiology. It is caused by specific virulent strains of Vibrio parahaemolyticus. Acute hepatopancreatic necrosis disease (AHPND) is a serious disease that has caused severe damage and significant financial losses to the global shrimp industry. Toxic AHPND-causing V. parahaemolyticus strains acquired a 63- to 70-kb plasmid encoding the binary toxins PirAvp/PirBvp, which are homologous to the Photorhabdus luminescens insect-related (Pir) toxins PirA/PirB. PirAvp/PirBvp are secreted toxins that were determined to be the primary virulence factors causing AHPND.