Oregano essential oil has the potential to reduce the virulence of Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease (AHPND) in Penaeus vannaei

Acute Hepatopancreatic Necrosis Disease (AHPND), caused by various species of Vibrio , results in significant mortality rates in global penaeid shrimp aquaculture. While antibiotics are commonly employed to combat this disease, concerns about the rapid emergence of resistant strains and their potential adverse effects on human health and the environment are rising. In this context, plant-derived essential oils have shown promising potential for controlling vibriosis in shrimp farming. This study investigated the antivirulence effects of oregano essential oil (OEO) at sub-minimum inhibitory concentrations (sub-MIC) on three virulence phenotypes (exopolysaccharide production, biofilm formation, and swarming motility) in V. parahaemolyticus the causative agent of AHPND. The antivirulence effect of OEO was validated through a challenge test by infecting Penaeus vannamei with V. parahaemolyticus cultured with and without OEO. Additionally, a transcriptomic analysis was performed to compare the transcriptional regulation of V. parahaemolyticus with and without OEO addition to identify therapeutic targets at the molecular level. The three virulence phenotypes were significantly inhibited (P < 0.05), with their effect being concentration-dependent. In the in vivo challenge, shrimp mortality infected with V. parahaemolyticus cultured with OEO (56 ± 5%) was significantly (P < 0.05) lower than in the control group (93 ± 5%). Transcriptomic analysis revealed 89 differentially expressed genes (DEGs) downregulated, associated with membrane integrity, ribosomes, motility, transport, type VI secretion system (T6SS), and enzymes involved in energy metabolism, and 94 DEGs upregulated, linked to biosynthetic processes, regulatory proteins, osmoadaptation, multidrug efflux transporters, ABC transporters, and zinc and nitrogen transport. These findings suggest that OEO targets multiple therapeutic pathways, inhibiting V. parahaemolyticus virulence. Our study demonstrates the significant antivirulence effect of OEO on V. parahaemolyticus , underscoring OEO's potential as a viable and eco-friendly alternative to traditional antibiotics for controlling AHPND in shrimp aquaculture.