Molecular Detection and Genetic Identification of Rickettsia Infection in Ixodes granulatus Ticks, an Incriminated Vector for Geographical Transmission in Taiwan.

Chien-Ming Shih,Li-Lian Chao,Pei-Wen Yang

doi:10.3390/microorganisms9061309

Abstract

Tick-borne Rickettsia pathogens have become an emerging source of zoonotic infections and have a major impact on human health worldwide. In this study, the prevalence and genetic identity of Rickettsia infections in Ixodes granulatus ticks was firstly determined in Kinmen Island of Taiwan. A total of 247 I. granulatus ticks were examined for Rickettsia infection by nested-PCR assay targeting the citrate synthase (gltA) gene of Rickettsia. The Rickettsia infection was detected with a general infection rate of 4.86%, and was detected in nymph, male and female stages with an infection rate of 3.81%, 0% and 6.84%, respectively. Phylogenetic relationships were analyzed by comparing the gltA sequences obtained from four Taiwan strains and 19 other strains representing 13 genospecies of Rickettsia. Phylogenetic analyses reveal that all Taiwan strains were genetically affiliated to the genospecies of spotted fever (R. parkeri) and transitional (R. felis) groups of Rickettsia. Our findings reveal the first detection of R. parkeri-like and R. felis in I. granulatus ticks from Kinmen Island. As a tourist island between Taiwan and mainland China, these results demonstrate the epidemiological significance of diverse Rickettsia species existed in I. granulatus ticks and highlight the potential threat of geographical transmission among humans in the Taiwan area.

Highlights

The genus Rickettsia is composed of approximately 27 species of obligate intracellular gram-negative bacteria that can be classified into four major groups: ancestral group (AG), typhus group (TG), transitional group (TRG) and spotted fever group (SFG) [1,2,3]
A total of 12 out of 247 (4.86%) I. granulatus ticks were detected with Rickettsia infection from Kinmen Island (Table 2)
Based on the life stage of ticks, the Rickettsia infection was detected in nymphs, males and females of I. granulatus ticks with an infection rate of 3.81%, 0% and 6.84%, respectively (Table 2)

Summary

Introduction

The genus Rickettsia is composed of approximately 27 species of obligate intracellular gram-negative bacteria that can be classified into four major groups: ancestral group (AG), typhus group (TG), transitional group (TRG) and spotted fever group (SFG) [1,2,3]. The. Ixodid ticks may serve as vectors and reservoirs of amplifying hosts for Rickettsia agents [4]. The SFG rickettsiae are mainly transmitted by vector ticks that can transmit the Rickettsia agents through the transovarial and transstadial pathways [5,6]. Rickettsia infections have become a global threat for emerging and re-emerging tick-borne diseases [7,8]. Global climate change has enhanced the geographical distribution of ticks and expanded the spread of tick-borne pathogens [9,10]. Most SFG rickettsioses are found in a particular geographic location [10,11,12,13,14,15,16], and many validated SFG rickettsial species have been discovered in Australia, Central and South America, and Asia [17,18,19,20,21,22,23,24,25]

Methods

Results

Discussion

Conclusion