Comparative analysis of nucleotide sequences of Orientia tsutsugamushi in different epidemic areas of scrub typhus in Shandong, China.

Scrub typhus, caused by Orientia tsutsugamushi, is a zoonosis that spreads rapidly in Shandong, China. To investigate the molecular characterization of O. tsutsugamushi in new and old epidemic areas in Shandong Province, we compared the genetic relationships of O. tsutsugamushi between Linyi and Tai'an districts, typical old and new epidemic areas in Shandong, respectively. O. tsutsugamushi was detected in blood from 12 of 16 patients in Linyi and in eschar from 3 of 4 patients in Tai'an; 17 of 128 rodents were found to be infected with O. tsutsugamushi in Linyi, and 4 of 68 rodents were found to be O. tsutsugamushi-positive in Tai'an. The results indicated less genetic variation in O. tsutsugamushi between the new and old epidemic areas, and the Sdu-1 type, similar to Japan Kawasaki, was the main genotype of O. tsutsugamushi in Shandong Province.