Metabarcoding detection of Vibrio species in black-tailed gulls reveals seabirds as overlooked sentinels of coastal zoonotic risk in South Korea.

The interface between urban coastal development and wildlife ecology creates critical, yet often overlooked, pathways for pathogen dissemination. This study evaluated the role of migratory Black-tailed Gulls (Larus crassirostris) as sentinels of zoonotic risk at the land-sea interface in South Korea. Using a two-tiered surveillance framework, we analyzed 75 faecal samples collected from anthropogenically influenced coastal sites (March-July 2023) by combining 16S rRNA gene metabarcoding with species-specific PCR targeting clinically relevant Vibrio spp. Metabarcoding detected Vibrio sequences in 58.67% of samples, with microbiota composition varying across coastal settings and suggesting links to local anthropogenic activities: seafood market-associated sites were dominated by Klebsiella and Rickettsiella, whereas tourist-dominated locations were characterized by Ligilactobacillus and Streptococcus. Targeted PCR confirmed the presence of V. parahaemolyticus (17.3%), V. cholerae non-O1/O139 (6.7%), and V. vulnificus (4.0%). Notably, the vvp virulence gene was detected in all V. vulnificus-positive samples, while other major virulence factors (ctxA, tdh, trh) were not detected. These findings provide the first molecular evidence in this region that wild gulls may act as mobile reservoirs of pathogenic Vibrio in anthropogenic coastal environments. Given the species' migration along the East Asian Flyway, this study highlights the value of integrating wildlife-based surveillance into One Health frameworks to better capture the transboundary dynamics of marine zoonoses.