Isolation of “pigeon-type” Chlamydia psittaci and detection of Chlamydia-related bacteria in Indian ring-necked parakeets (Psittacula krameri manillensis) in introduced flocks in urban area of Japan

Introduced as an exotic species, Indian ring-necked parakeets (Psittacula krameri manillensis) are now established in urban areas of Japan in flocks exceeding 1000 birds. The release of exotic animals into the wild and the establishment of new populations have led to conservation and disease prevention challenges. With these parakeets sharing their habitat with humans, their feces accumulating in human living areas may pose a public health risk of transmitting Chlamydia psittaci. Herein, we investigated the prevalence of Chlamydiales in wild Indian ring-necked parakeets. We examined 66 faecal samples from wild Indian ring-necked parakeets using molecular methods and detected three samples positive for C. psittaci. The positivity rate for C. psittaci was 4.5 % (3/66) across all samples and 18.8 % (3/16) for the sampled location. Additionally, Chlamydia-related bacteria were detected. Three strains of C. psittaci were successfully isolated using HeLa cells, and the NRM_5 strain was subjected to whole-genome sequencing to determine the complete genome sequence. NRM_5 showed the highest sequence similarity to MN strain, and exhibited the sequence type is ST35, commonly associated with pigeons and doves, indicating the potential for transmission among bird species.