Ehrlichiosis and zoonotic anaplasmosis in suburban areas of Beijing, China.

In 2006, an unusual nosocomial outbreak of anaplasmosis occurred in Anhui Province, China. To follow these emerging tickborne-rickettsioses, a larger survey of Ehrlichia chaffeensis and Anaplasma phagocytophilum seroprevalence among farm worker populations, and the divergence of the partial 16S rRNA gene sequences of A. phagocytophilum among domestic animals, were conducted in Yanqing, Miyun, and Tongzhou Counties in Beijing from March to April, 2009. Blood samples from 562 farmers, 90 goats, 73 cattle, and 2 dogs were collected. IgG antibodies against E. chaffeensis and A. phagocytophilum were assayed by micro-indirect immunofluorescence assay (IFA). Partial fragments of 16S rRNA genes of A. phagocytophilum were amplified from blood DNA from domestic animals and their sequences analyzed. The total E. chaffeensis and A. phagocytophilum seroprevalence among the farm worker population was 16.4% and 14.1%, respectively. For domestic animals, the seropositive rates of A. phagocytophilum for goats, cattle, and dogs, were 2.3%, 0%, and 0%, respectively. The PCR-positive rates for A. phagocytophilum in goats and cattle were 48.9% and 23.9%, respectively. Three dominant genetic groups of Chinese A. phagocytophilum isolates were determined for goats and cattle, and these isolate varieties were broadly identified in China, Japan, and Korea. The prevalence of E. chaffeensis and A. phagocytophilum among farmers and domestic animals in Beijing rural areas was also demonstrated. The diagnoses and differential diagnoses of these emerging infectious diseases should be emphasized in clinics, and further ecological investigation of E. chaffeensis and A. phagocytophilum vectors and hosts is needed.