Chlamydia Species and Related Risk Factors in Poultry in North-Western Italy: Possible Bird-to-Human Transmission for .

are obligatory intracellular bacteria causing acute and chronic diseases in animals and humans worldwide, with recently discovered species with a still unclear pathogenic potential (i.e., ). In Italy, infections are underestimated both in animals and humans. To estimate the prevalence of species in poultry and occupationally exposed workers on farm, a cross-sectional study was carried out in north-western Italy. A total of 2063 samples from 83 commercial and 31 backyard poultry farms were analysed using real-time PCRs for screening and species typing. were detected in 23 farms, with a herd prevalence of 20.2% (95%CI: 13.2-28.7), higher in backyard farms (38.7%; 95%CI: 21.8-57.8) compared to commercial ones (13.3%; 95%CI: 6.8-22.5). was found in 18 chicken farms, both commercial and backyard, and only in 3 backyard farms. Exposure to wild birds and factors related to biosecurity resulted the main risk factors associated with positivity. Out of the 113 sputum samples collected from farmers, 16 tested positive to with a prevalence of 14.2% (95%CI: 8, 3-22). To the best of our knowledge, for the first time at international level, was detected in humans with farmer positivity associated with farm infectious status, suggesting a bird-to-human transmission.