Molecular prevalence of Chlamydia spp. in wild birds from Qinghai Lake, China.

Chlamydia spp. are a group of gram-negative, obligate intracellular bacteria that represent significant pathogens causing chlamydiosis in both animals and humans. Avian chlamydiosis (AC), primarily caused by Chlamydia psittaci, C. avium, C. gallinacea, and C. ibidis, has been documented in over 460 avian species. Qinghai Lake, China's largest saltwater lake and a critical overwintering site for migratory birds, served as the study area to investigate Chlamydia prevalence in wild birds. Fecal samples from 125 birds revealed an overall Chlamydia spp. infection rate of 28.8% (36/125), with three species identified: C. abortus (55.6%, 20/36), C. avium (44.4%, 16/36), and C. psittaci (13.9%, 5/36). Phylogenetic analysis through amplification of the 16 S rRNA (5 samples), IGS-23 S rRNA (6 samples), and ompA (5 samples) genes revealed that all sequences obtained in this study were assigned to the Chlamydiaceae family. The ompA sequence of C. abortus obtained in this study clustered closely with the reference strain GN6 (CP021996.1) isolated from aborted yak fetuses (Bos grunniens), a bovid species typically domesticated and endemic to the Qinghai-Tibet Plateau, showing 100% sequence identity. In contrast, C. avium ompA sequences shared 87.40% identity with the reference strain 10DC88. The identical genomic profile of C. abortus between wild birds and domesticated yaks suggests potential cross-species transmission in the Qinghai-Tibetan Plateau, where overlapping habitats of wildlife and livestock may facilitate pathogen exchange. These findings underscore the zoonotic risks posed by Chlamydia species circulating in this ecologically critical region, with implications for the health of local livestock (yaks, Tibetan sheep), human populations, and migratory bird conservation.