Seroprevalence and risk factors of Chlamydia infection in dogs in Southwestern China

Chlamydia spp. are obligate intracellular bacteria distributed globally, known to cause various forms of diseases in animals and humans. To date, there is limited information about the seroprevalence of Chlamydia and the risk factors associated with Chlamydia infection in dogs in the world. In the present study, a serological survey was undertaken to examine the seroprevalence and risk factors associated with dog chlamydiosis in Yunnan Province, southwestern China. A total of 591 dogs were sampled, antibodies to Chlamydia were determined by indirect hemagglutination assay (IHA). The overall seroprevalence was estimated at 17.6%. The risk factors associated with seroprevalence were determined by a multivariate logistic regression analysis. Gender and age of dogs were not significant in the logistic regression analysis (P > 0.05) and left out of the final model. Type and geographical origin of dogs were considered as main risk factors associated with Chlamydia infection, stray dogs (31.37%) were more than 16 times (OR = 16.167, 95% CI = 6.283–41.599, P < 0.01) at risk of acquiring the infection compared to the police dogs (7.62%), while pet dogs (14.41%) had a 3 times (OR = 2.968, 95% CI = 1.349–6.529, P = 0.007) higher risk. Positive dogs were found in 5 districts of Yunnan Province with prevalence ranging from 2.56% to 31.67% except Diqing (0/56). Dogs in Kunming (20.21%) had a 9 times higher risk of being seropositive compared to dogs in Lijiang (2.56%) (OR = 9.057, 95% CI = 1.211–67.714, P = 0.032), although no regional differences were found in other 4 administrative divisions compared to Lijiang (P > 0.05). Our study revealed a widespread and high prevalence of Chlamydia infection in dogs in Yunnan Province, southwestern China, with higher exposure risk in stray dogs and distinct geographical distribution. These findings suggest the potential importance of dogs in the transmission of zoonotic Chlamydia infection, and thus Chlamydia should be taken into consideration in diagnosing dog diseases.