Prevalence and molecular characterization of Acute hepatopancreatic necrosis disease (AHPND) in cultured white-leg shrimp Litopenaeus vannamei with the fungal bioactive control strategy

Mass mortalities with clinical signs characteristic of acute hepatopancreatic necrosis disease (AHPND) were reported in cultured Litopenaeus vannamei from three Egyptian farms: Wadi-Mariote, Berket Ghalyoun, and Qarun Lake. During 4-month surveillance in 2023, shrimp samples were collected to investigate the prevalence of AHPND-causing Vibrio parahaemolyticus (Vp_AHPND) based upon phenotypic identification, PCR, and DNA sequencing of pirA genes and pirB toxin genes followed by maximum likelihood phylogenetic analysis. In addition, the pathogenicity of V. parahaemolyticus was evaluated through the injection challenge and histopathological examination. Moreover, the antibacterial activity of marine fungal extracts against identified V. parahaemolyticus was also assessed. Molecular analysis confirmed both pirA (282 bp) and pirB (392 bp) toxin genes in the bacterial isolates. A significant positive correlation (P < 0.05) was found between V. parahaemolyticus levels in shrimp and pond water samples throughout the study period. Injection challenge with 2.7 × 10⁴ CFU bacterial suspension resulted in 63.33 % mortality in challenged shrimp, with typical AHPND clinical signs. The histopathological examination revealed degenerative changes, including atrophy, necrosis, and sloughing of hepatopancreatic tubule epithelial cells, along with loss of functional hepatopancreatic cells. Among 11 fungal isolates screened for anti-vibrio activity, Aspergillus niger HMA9 showed the strongest inhibitory effect against V. parahaemolyticus. This study provides the first genetic confirmation of pirA and pirB toxin genes in Vp_AHPND as the cause of L. vannamei mass mortalities in Egypt. Further, it demonstrates the potential of fungal bioactive compounds for controlling AHPND in shrimp aquaculture.