Characterization of rickettsiae in ticks in northeastern China.

Huanhuan Liu,Feng Wei,Mingxin Song,Xiaozhuo Zhang,Zedong Wang,Qihong Li,Zhongyu Li,Shuchao Wang,Quan Liu

doi:10.1186/s13071-016-1764-2

Abstract

BackgroundTick-borne rickettsioses are considered important emerging zoonoses worldwide, but their etiological agents, rickettsiae, remain poorly characterized in northeastern China, where many human cases have been reported during the past several years. Here, we determined the characteristics of Rickettsia spp. infections in ticks in this area.MethodsTicks were collected by flagging vegetation from Jilin and Heilongjiang provinces of northeastern China followed by morphological identification. The presence of Rickettsia spp. in ticks was detected by PCR targeting the 23S-5S ribosomal RNA intergenic spacer, citrate synthase (gltA) gene, and 190-kDa outer membrane protein gene (ompA). The newly-generated sequences were subjected to phylogenetic analysis using the software MEGA 6.0.ResultsThe overall infection rate of Rickettsia spp. was 6.12 %. Phylogenetic analyses based on the partial gltA and ompA genes demonstrated that rickettsiae detected in the ticks belong to four species, including “Candidatus Rickettsia tarasevichiae”, Rickettsia heilongjiangensis, Rickettsia raoultii, and a potential new species isolate. The associated tick species were also identified, i.e. Dermacentor nuttalli and Dermacentor silvarum for R. raoultii, Haemaphysalis concinna and Haemaphysalis longicornis for R. heilongjiangensis, and Ixodes persulcatus for “Ca. R. tarasevichiae”. All Rickettsia spp. showed significantly high infection rates in ticks from Heilongjiang when compared to Jilin Province.ConclusionRickettsia heilongjiangensis, R. raoultii and “Ca. R. tarasevichiae” are widely present in the associated ticks in northeastern China, but more prevalent in Heilongjiang Province. The data of this study increase the information on the distribution of Rickettsia spp. in northeastern China, which have important public health implications in consideration of their recent association with human diseases.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1764-2) contains supplementary material, which is available to authorized users.

Highlights

Tick-borne rickettsioses are considered important emerging zoonoses worldwide, but their etiological agents, rickettsiae, remain poorly characterized in northeastern China, where many human cases have been reported during the past several years
122 tick pools out of 2928 (6.12 %) ticks were found positive for Rickettsia spp
We determined that D. nuttalli, D. silvarum, H. concinna, H. longicornis and especially I. persulcatus were the major tick species, and acting mainly as vectors for R. raoultii, R. heilongjiangensis and “Ca. R. tarasevichiae”, respectively, in northeastern China

Summary

Introduction

Tick-borne rickettsioses are considered important emerging zoonoses worldwide, but their etiological agents, rickettsiae, remain poorly characterized in northeastern China, where many human cases have been reported during the past several years. Tick-borne rickettsioses are considered important emerging zoonoses worldwide, due to tick distribution alterations, shifting climates, and accelerating urbanization [4, 5] These diseases share characteristic clinical features, including fever, asthenia, At least nine species or subspecies of tick-borne rickettsiae have been identified during the past 30 years in China, including Rickettsia heilongjiangensis, Rickettsia sibirica sp BJ-90, Rickettsia raoultii and “Candidatus Rickettsia tarasevichiae” [6,7,8,9]. Rickettsia heilongjiangensis was primarily identified in Suifenhe and Luobei of Heilongjiang Province in 1984, and isolated from the blood of a tick-bitten patient in the same place ten years later [10,11,12].

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