Identification of Parachlamydiaceae DNA in nasal and rectal passages of healthy dairy cattle

Aims The order Chlamydiales comprises a broad range of bacterial pathogens and endosymbionts, which infect a wide variety of host species. Within this order, members of the family Parachlamydiaceae, which includes Parachlamydia and Neochlamydia species, have been particularly associated with infections in both humans and cattle, including having a potential pathogenic role in cases of bovine abortion. While the route of transmission has yet to be defined, it has been hypothesised that asymptomatic carriage and contamination of the immediate environment may be a route of inter-animal transmission. We investigated the asymptomatic carriage of Chlamydia-related organisms in healthy cattle. Methods & Results DNA was isolated from nasal and rectal swabs obtained from 38 healthy dairy heifers. A Chlamydiales sp. 16S rRNA qPCR was performed on each sample. A total of 18/38 nasal samples and all 38/38 rectal samples were identified as positive for Chlamydiales sp. Each positive sample was sequenced confirming the presence of DNA belonging to the Parachlamydiaceae. Conclusions The presence of Parachlamydiaceae DNA in nasal and rectal swab samples of healthy cattle provides evidence for the asymptomatic carriage of parachlamydial organisms within cattle. Significance & Impact of the Study The study provides evidence of potential routes of environmental contamination that could provide a route for inter-animal and animal transmission of Parachlamydiaceae