Human-pathogenic Anaplasma spp., and Rickettsia spp. in animals in Xi’an, China

In China, thirteen species of tick-borne rickettsiales bacteria pathogenic to human have been reported in ticks and host animals, and human patients caused by them also has been identified.However, investigation for rickettsiales bacteria circulating in Xi'an wasn't performed although diseases resembling human diseases caused by these organisms have been found.In this study, domestic animals and ticks in Xi'an, China, were tested for the presence of rickettsiales bacteria pathogenic to humans.Besides A. ovis, a high prevalence of A. capra was observed suggesting a high public health risk exists.In addition, two novel Anaplasma species closely related to A. phagocytophilum were identified and formed distinct lineages in the phylogenetic trees, with more than 98.3% identities for rrs gene, while divergences up to 20.2% and 37.0% for groEL and gltA genes, respectively.Both of these two novel Anaplasma species were found to circulate in goats and further assessment of their pathogenicity is needed.Ca.R. jingxinensis, with potential pathogenicity, was also detected in H. longicomis ticks with high prevalence.However, other causative agents were not identified although they were distributed in other areas of China. Author summaryChina is severely affected by rickettsial diseases caused by rickettsiales bacteria.To date, at least 13 tick-borne rickettsiales bacteria have been reported in China.In this study, we perform molecular epidemiological investigations of rickettsiales bacteria circulating in Xi'an.Through sampling in Xi'an, we show that high prevalence of Anaplasma capra in ticks and domestic animals.In addition, A. ovis and two potentially novel Anaplasma species closely related to A. phagocytophilum are also identified in goats.Besides Anaplasma, Candidatus Rickettsia jingxinensis, a tentative Rickettsia species potential pathogenic to human, is also detected in H. longicomis ticks with high prevalence.Although our study shows that human-pathogenic rickettsiales bacteria exist in Xi'an, the association between them with the non-viral hemorrhagic fever with renal syndrome (HFRS) cases should be confirmed in further study.In sum, A. capra and Ca.R. jingxinensis infected in domestic