Molecular Survey and Genetic Analysis of Ehrlichia canis in Rhipicephalus sanguineus Ticks Infesting Dogs in Northern Taiwan.

Abstract

Ehrlichia canis is a tick-transmitted zoonotic pathogen in dogs. We conducted a molecular survey for screening of E. canis infection in Rhipicephalus sanguineus ticks infesting dogs and identified its genetic identity in Taiwan. A total of 1195 R. sanguineus ticks were collected and examined for Ehrlichia infection by nested-PCR assay targeting the 16S ribosomal RNA (rRNA) gene. In general, Ehrlichia infection was detected in 1.5% of examined ticks, and was detected in nymph, male and female stages with infection rates of 0.6%, 1.31% and 2.76%, respectively. The highest monthly prevalence was observed in August with an infection rate of 5.91%. Genetic identity was analyzed by comparing the 16S rRNA gene sequences obtained from 11 Taiwan strains and 15 other strains representing five genospecies of Ehrlichia spp., including two outgroups (Anaplasma phagocytophilum and Rickettsia rickettsii). Results revealed that all Taiwan strains were genetically affiliated to the same clade within various E. canis strains documented in GenBank with a high sequence similarity (99.7-100%) and that they can be clearly distinguished from other genospecies of Ehrlichia. This study provides the first evidence of E. canis identified in R. sanguineus ticks and highlights the potential threat for human infections in Taiwan.