Investigation on scrub typhus in Yongshan County,Yunnan Province,China / 中国人兽共患病学报

ABSTRACT

We investigated epidemiological characteristic of scrub typhus in Yongshan County,Yunnan Province,China. The serum samples were collected from the patients with fever for detecting the antibody against Orientia tsutsugamsushi (Ot) by colloidal gold immunoassay assay.Rat traps were used to capture rodents.The spleen tissues of the captured rodents were detected by nested-polymerase chain reaction for rickettsia groEL segment.The groEL segments were sequenced and analyzed the homology with the other known sequences.Thirty-four scrub typhus cases were found in Yongshan County,Yunnan Prov-ince from May 2015 to October 2015.Among them,21 cases were confirmed by laboratory tests and 13 cases were clinical di-agnosis diseases.Of these patients,32.35% of the cases occurred in June.The 32.35% were in the group of the 40-49 year-old,and 79.41% were farmers,94.12% exhibited eschar or skin ulcer(31.25% were observed in groin of these cases),and rash developed in 50%.In 39 spleen tissue samples of Rattus flavipectus,9 samples showed positive for groEL gene Ot,but gro-EL gene of Typhus group rickettsia and spotted fever group rickettsia were negative.Sequence analysis showed that YSP30 was closely related to some Saitama related strains of Ot,such as HSB1,FAR1 and UAP4,while the other 8 strains were closely related to some Karp related strains of Ot,such as UT213,UT221 and SH205.It was confirmed that the Yongshan County was the natural foci of scrub typhus by the serological and molecular biological detections.There are Karp and Saitama genotype related Ots in the natural foci.