Molecular Detection of Blastocystis Subtypes ST7 and ST26 in Fecal Samples from Black-Headed Gulls in Kunming, China

Migratory birds are potential carriers for the cross-regional spread of zoonotic diseases due to their high mobility and extensive geographical activity range. Blastocystis, a ubiquitous parasitic protist, can infect a broad spectrum of animal hosts including humans, constituting a potential public health hazard. Currently, data on Blastocystis infection in black-headed gulls (Chroicocephalus ridibundus) remain scarce. This study aimed to investigate the fecal sample positivity rate, epidemiological characteristics, and subtype distribution of Blastocystis in wintering black-headed gulls in Kunming, China. A total of 245 fresh fecal samples were collected from black-headed gulls in Kunming, Yunnan Province, during December 2025 and January 2026. Fecal DNA was extracted and subjected to PCR amplification targeting the small subunit ribosomal RNA (SSU rRNA) gene of Blastocystis. Results showed a 3.27% (8/245) overall Blastocystis fecal sample positivity rate in wintering black-headed gulls, with two subtypes detected: dominant zoonotic pathogenic ST7 (87.5%, 7/8) and ruminant-adapted ST26 (12.5%, 1/8). This study represents the first report of Blastocystis in black-headed gulls in China, providing data supporting the understanding of genetic subtype diversity of Blastocystis in avian hosts.