Phylogenetic Analysis of Spotted Fever Group Rickettsia Gene from Ticks and Human Patients in Tottori Prefecture, Japan.

BACKGROUND

Japanese spotted fever (JSF) is a tick-borne bacterial febrile disease caused by characterized by fever, rash, and occasional death. The number of patients in Japan and the Tottori Prefecture has been increasing over the past 20 years. Most cases were found in Eastern Tottori; however, the distribution of patients has expanded to the Central and Western regions. Ticks carried by wild animals may be the cause, but the prevalence of in ticks has not yet been analyzed.

METHODS

Ticks were collected by flagging-dragging from 16 sites in Tottori, Japan. The ticks were morphologically classified and DNA was extracted. The 17-kDa antigen gene was amplified using nested PCR. PCR amplicons from ticks and JSF patients were sequenced and phylogenetically compared.

RESULTS

In total, 177 ticks were collected and identified as The Spotted Fever Group Rickettsia (SFGR) was detected in and spp. using PCR, with positivity rates of 36.8% and 33.3%, respectively. DNA sequencing and phylogenetic analysis revealed that positive ticks harbored , , and other Rickettsiae species; however, the patient's samples were restricted to . Similar to the incidence of JSF, the rate of -positive ticks was higher in the Eastern region; however, -positive ticks were also detected in the Western region.

CONCLUSION

sequences had been found in ticks collected in Tottori Prefecture. Ticks harboring were found in the Eastern and Western parts of Tottori Prefecture and the sequences were identical to the human cases. Only the sequence has been detected in patients with spotted fever symptoms, even though ticks were harboring various SFGRs.