Determination of Scrub typhus Suggests a New Epidemic Focus in the Anhui Province of China

In 2007, 19 cases of a scrub typhus epidemic occurred within a week at a sports school in Mingguang County, Anhui Province, where no previous incidence of this mite borne disease had been reported. Sero-surveillance in 2009 indicated that 10 of the 100 school students possessed anti-Orientia tsutsugamushi antibodies. From 2009 to 2013, 60 small animals and 2250 mites were collected in the vicinity of the school. 5 of the Apodemus agrarius samples and 1 group of Leptotrombidium linhuaikongense tested positive via PCR for O. tsutsugamushi. Two strains of O. tsutsugamushi were identified by injecting Kun Ming (KM) mice peritoneally with the organs of either Apodemus agrarius or Leptotrombidium linhuaikongense. Apart from sharing 98% homology with the O. tsutsugamushi Yongworl strain, genes encoding the membrane protein from the two O. tsutsugamushi isolates shared > 99% sequence homology with each other, reflecting the consistency of the pathogen in both the vector and the host. In addition, we also characterized a chronic scrub typhus infection in a local patient. The membrane protein gene fragment from the patient's blood shared 99% homology with O. tsutsugamushi Gilliam strain, suggesting that more than one O. tsutsugamushi strain is present at this location.