Susceptibility of Lion's paw scallop (Nodipecten subnodosus) juveniles to a pirAB-positive Vibrio campbellii strain isolated from Litopenaeus vannamei shrimp affected by Acute Hepatopancreatic Necrosis Disease (AHPND).

Acute hepatopancreatic necrosis disease (AHPND) is a serious bacterial infection affecting penaeid shrimp, caused primarily by Vibrio species harboring the pirAB toxin genes. While AHPND has been studied extensively in shrimp, its potential impact on other marine invertebrates remains largely unexplored. This study evaluates, for the first time, the susceptibility of juvenile lion's paw scallops (Nodipecten subnodosus) to AHPND-associated Vibrio campbellii (VCAHPND-VP3) strains isolated from Litopenaeus vannamei shrimp outbreaks. Experimental infection by immersion assays demonstrated a dose-dependent response, with 100 % cumulative mortality at 5 × 106 CFU/mL, while lower concentrations resulted in subclinical infections. The presence of VCAHPND-VP3 in gill and stomach tissues was confirmed by nested PCR detection of pirAB genes. Comparative pathogenicity assays between VCAHPND-VP3 and the native Vibrio alginolyticus strain revealed that, despite similar rates of bacterial uptake, only VCAHPND-VP3 caused high mortality, highlighting the critical role of PirAB toxins in virulence. Whole genome sequencing of the VCAHPND-VP3 strain confirmed the presence of the pirAB-carrying plasmid, previously reported as pVA1 and revealed additional genes associated with pathogenicity and mobile genetic elements. These results confirm the susceptibility of mollusk species to AHPND-associated Vibrio and highlight potential ecological risks related to the dissemination of pirAB-positive vibrios in coastal environments.