Black-Tailed Gull (Larus crassirostris): A Novel Host for Trichomonas gypaetinii with High Prevalence of Avian Trichomonads in South Korea

This study detected Trichomonas gypaetinii in Black-tailed Gulls (Larus crassirostris) in South Korea. We collected 83 samples (80 oropharyngeal swabs from live birds and three carcass-derived specimens) from breeding colonies on Nando and Hongdo islands and coastal habitats in Taean, South Korea, in 2023-24. Molecular analysis using nested PCR targeting the ITS region revealed an exceptionally high prevalence (98.8%) of Trichomonas spp., with both Trichomonas gallinae and Trichomonas gypaetinii identified. We observed significant seasonal variation in Trichomonas spp. distribution, with T. gallinae predominating in winter (85%), while T. gypaetinii became more prevalent during breeding and migration periods (67%). Co-infections were documented at both breeding colonies, suggesting potential interspecies interactions. Sex-based differences in infection patterns were statistically significant (P