Genotype diversity and distribution of Orientia tsutsugamushi in scrub typhus patients and rodents in Shandong, northern China

Abstract

Orientia tsutsugamushi, the etiologic agent of scrub typhus, is transmitted to humans through the bites of infected chiggers. To identify the genotypes of O.tsutsugamushi and their geographical distribution in Shandong, 236 patient's samples and 1606 captured rodents were collected in major-endemic regions of Shandong Province from June 2013 to December 2014. Sequences were determined for the 56-kDa TSA gene, and the relationship between these sequences and those previously determined was assessed. Two genotypes out of 5 previously reported in Shandong were identified, i.e. Kawasaki-related and STA-07. The Kawasaki-related genotype was predominant (82.1% (23/28) in human and 50% (5/10) in rodents), with wide distribution through the endemic areas of Shandong Province. The STA-07 was confined to Tai'an, Linyi and Qingdao districts. The Fuji-related, Shimikoshi-related and Karp-related genotypes were not found, while identified in previous studies. For prevention and control of scrub typhus in Shandong, more attention should be paid to surveillance of Kawasaki-related and STA-07 genotypes.

Keywords: 56-kDa type specific antigen gene; Geographic distribution; Orientia tsutsugamushi; Phylogenetic analysis; Scrub typhus.