Novel spotted fever group rickettsiae in Haemaphysalis qinghaiensis ticks from Gansu, Northwest China.

Jifei Yang,Junlong Liu,Zhijie Liu,Jianxun Luo,Guiquan Guan,Rong Han,Guangyuan Liu,Zhancheng Tian,Hong Yin,Youquan Li,Qingli Niu

doi:10.1186/s13071-016-1423-7

Abstract

BackgroundRickettsia spp. are obligate intracellular bacteria and well known as transmitted by arthropods. These pathogens have a broad geographic distribution and a high degree of biological and clinical diversity. This study was conducted to determine the prevalence and molecular characterization of Rickettsia spp. in ticks collected from Gansu, where Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum were previously reported in ticks and ruminants.MethodsA total of 1,583 questing Haemaphysalis qinghaiensis ticks were collected and tested for the presence of Rickettsia spp. gltA gene by PCR. Samples positive for gltA were examined by specific primers targeted for the ompA gene of SFG rickettsiae. The infections were further validated by sequencing and positive samples were genetically characterized based on the gltA and ompA genes.ResultsIn total, Rickettsia spp. infection was found in 179 (18.5 %) H. qinghaiensis tick pools by using PCR and primers specific for the gltA gene. Of those, 157 (16.3 %) tick pools were positive for SFG rickettsiae by PCR based on ompA gene. Amplification and molecular analysis of the nucleotide sequences of gltA and ompA genes indicated three potential novel spotted fever group rickettsiae in H. qinghaiensis ticks. These three potential novel spotted fever group rickettsiae were clustered together in a subgroup, which represents a sister taxon to and separates from other known four SFG rickettsiae subgroups.ConclusionsThis study revealed a high infection rate of SFG rickettsiae in H. qinghaiensis ticks in northwest China. Three potential novel spotted fever group rickettsiae classified into a novel SFG rickettsiae subgroup were identified and named “Candidatus Rickettsia gannanii” related strains in recognition of the location where it was first detected.

Highlights

Rickettsia spp. are obligate intracellular bacteria and well known as transmitted by arthropods
Most of the recently discovered pathogenic Rickettsia spp. were first identified in arthropods and much later were reported in human cases, such as R. parkeri and R. slovaca. The former was identified in Amblyomma maculatum in 1937, and it was not until 60 years later that the first human case of R. parkeri infection was described [14]; the latter was described in Dermacentor marginatus in 1968, but the first documented case was reported several years later [1]
With the development of molecular techniques, new Rickettsia spp. have been identified in places where no rickettsioses had been reported, and some of these have been recognized as human pathogens [15]

Summary

Introduction

Rickettsia spp. are obligate intracellular bacteria and well known as transmitted by arthropods. These pathogens have a broad geographic distribution and a high degree of biological and clinical diversity. Most of the recently discovered pathogenic Rickettsia spp. were first identified in arthropods and much later were reported in human cases, such as R. parkeri and R. slovaca. With the development of molecular techniques, new Rickettsia spp. have been identified in places where no rickettsioses had been reported, and some of these have been recognized as human pathogens [15]. The objective of this study was to identify the rickettsial species in ticks collected from a specific area of QingTibetan Plateau that had not been previously described for rickettsioses

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Conclusion