Dogs as New Hosts for the Emerging Zoonotic Pathogen Anaplasma capra in China

Anaplasma capra is an emerging zoonotic tick-borne pathogen with a broad host range, including many mammals. Dogs have close physical interactions with humans and regular contact with the external environment. Moreover, they have been previously reported to be hosts of Anaplasma phagocytophilum, A. platys, A. ovis, and A. bovis. To confirm whether dogs are also hosts of A. capra, pathogen DNA was extracted from blood samples of 521 dogs, followed by PCR amplification of the citrate synthase (gltA) gene, heat shock protein (groEL) gene, and major surface protein 4 (msp4) gene of the A. capra. A total of 12.1% (63/521) of blood samples were shown to be A. capra-positive by PCR screening. No significant differences were observed between genders (P = 0.578) or types (P = 0.154) of dogs with A. capra infections. However, significantly higher A. capra infections occurred in dogs with regular contact with vegetation (P = 0.002), those aged over 10 years (P = 0.040), and during the summer season (P = 0.006). Phylogenetic analysis based on gltA, groEL, and msp4 sequences demonstrated that the isolates obtained in this study were clustered within the A. capra clade, and were distinct from other Anaplasma species. In conclusion, dogs were shown to be a host of the human pathogenic A. capra. Considering the affinity between dogs and humans and the zoonotic tick-borne nature of A. capra, dogs should be carefully monitored for the presence of A. capra.