To understand the natural infection of Orientia tsutsugamushi among rodent animals in central Zhejiang and its molecular biological characteristics.

Low hilly regions and residential regions of three survey sites in Yiwu were selected and 687 rodent animals were captured from March to November 2015. groEL gene of O. tsutsugamushi in the livers and spleens were detected and sequenced by PCR. The evolutionary analyse was conducted by Maximum Likelihood method of MEGA7.0 software. The time tree was generated by Reltime method to estimate divergence times for all branching points in the topology.

Of 687 rodent animals captured, 26 were positive for O. tsutsugamushi and the infection rate was 3.78%. There were 352 rodent animals captured from March to July and groEL were negative. While there were 355 rodent animals captured from August to November and 26 were groEL-positive. The infection rates for O. tsutsugamushi were high in September and October, accounting for 11.32% (6/53) and 10.00% (9/90) , respectively. The trend of infection rate was increasing (χ²_trend=25.85, P<0.01) . O. tsutsugamushi infection existed in four dominant mice species including Eothenomys melanogaster, A. agrarius, Niviventer fulvescens and Suncus murinus. Of those, the infection rate was the highest inA. agrarius of 8.67% (13/150) . Of 26 positive rodent animals, 25 were captured in the field and 25 were captured in Dachen town. The alignment and phylogenetic analysis showed that the groEL gene sequences were different obviously. O. tsutsugamushi genotypes including Kato, Boryong, O3 and other unknown genotypes were likely to exist among rodents in Yiwu region. The time tree analysis showed that emerging times of the different strains in Yiwu were inconsistent.

O. tsutsugamushi infection exists in rodents in central Zhejiang. The groEL gene distributes in different strains.

Rodentia; Rickettsiae; Orientia tsutsugamushi; Genotype