Transmission cycle of Shimokoshi type Orientia tsutsugamushi in Shimane Prefecture, Japan.

To demonstrate the transmission cycle of Shimokoshi type Orientia tsutsugamushi in Shimane prefecture, field rodents were captured from areas where four human infections caused by the pathogen were reported. The rodents were investigated for the transmission cycle of the pathogen based on the pathogen's genome, antibodies against the pathogen, and vector of the pathogen (Leptotrombidium palpale). In addition, the vector was captured from soil of the study areas. A total of 44 rodents was captured. No DNA of O. tsutsugamushi were detected in the blood or spleen samples using real-time polymerase chain reaction. However, the specific antibody against the pathogen was detected in 2 out of 44 (4.5%) rodents by the indirect immunoperoxidase method, indicating the presence of the pathogen in the study areas. Although 29 L. palpale were identified, DNA detection was not performed, because of insufficient number of vectors according to the DNA detection rate in previous studies. However, the identification of the vector as well as the specific antibody in rodents suggest the presence of the transmission cycle of Shimokoshi type O. tsutsugamushi in Shimane prefecture.