Detection of a novel enterotropic Mycoplasma gallisepticum-like in European Starling (Sturnus vulgaris) around poultry farms in France

Recent outbreaks of highly pathogenic avian influenza in southwest France have raised questions regarding the role of commensal wild birds in the introduction and dissemination of pathogens between poultry farms. To assess possible infectious contacts at the wild-domestic bird interface, the presence of Mycoplasma gallisepticum (MG) was studied in the two sympatric compartments in southwest France. Among various peridomestic wild birds (n=385), standard PCR primers targeting the 16S rRNA of MG showed a high apparent prevalence (up to 45%) in cloacal swabs of European starlings (Sturnus vulgaris, n=108), while the MG-specific mgc2 gene was not detected. No tracheal swab of these birds tested positive, and no clinical sign was observed in positive birds, suggesting commensalism in the digestive tract of starlings. A mycoplasma strain was then isolated from a starling swab and its whole genome was sequenced using both Illumina and Nanopore technologies. Phylogenetic analysis showed that it was closely related to MG and M. tullyi, although it was a distinct species. A pair of specific PCR primers targeting the mgc2-like gene of this MG-like strain was designed and used to screen again the same avian populations and a wintering urban population of starlings (n=50). Previous PCR results obtained in starlings were confirmed to be mostly due to this strain (20/22 positive pools). In contrast, the strain was not detected in fresh faeces of urban starlings. Furthermore, it was detected in one tracheal pool of cattle egrets and one cloacal pool of white wagtails, suggesting infectious transmissions between synanthropic birds with similar feeding behaviour. As the new starling mycoplasma was not detected in free-range ducks (n=80) in close contact with positive starlings, nor in backyard (n=320) and free-range commercial (n=720) chickens of the area, it might not infect poultry. However, it could be involved in mycoplasma gene transfer in such multi-species contexts.