Lyme Disease in Canada

Ticks of the genus Dermacentor are important vectors of human and animal pathogens in North America. They also carry a variety of endosymbiotic (i.e. non-pathogenic) bacteria. The American dog tick, D. variabilis, is known to be infected with gammaproteobacteria of the genus Arsenophonus. However, there have been no previous reports of Arsenophonus-type bacteria in the Rocky Mountain wood tick, D. andersoni, a species that is sympatric with D. variabilis in the western parts of its distributional range. In this study, the presence of Arsenophonus-type bacteria was determined by PCR and DNA sequencing for 338 D. andersoni and 448 D. variabilis adults from western Canada. Fifty-one (15%) of the D. andersoni were found to be infected with Arsenophonus, whereas only a single D. variabilis was infected. The prevalence of Arsenophonus in D. andersoni varied among localities (0-27%). The 16S rDNA sequences of Arsenophonus in Canadian D. andersoni and D. variabilis were identical to one another, but the results of a phylogenetic analysis showed that they were genetically distinct from, and may represent a different species to, the Arsenophonus in D. variabilis and Amblyomma americanum in eastern USA.