Ehrlichia DNA detected in Dermacentor albipictus (winter tick) collected from a moose in western Canada

Anaplasma and Ehrlichia are obligate intracellular organisms that infect blood cells of animals and these bacteria are often pathogenic to their hosts. New strains or species of Anaplasmataceae have been identified from various species of tick and/or vertebrate host over the last several years, but their taxonomic position and relevance to animal health are largely unknown. All known species of Anaplasma and Ehrlichia are transmitted by various species of ticks, including Dermacentor.

In this study, 933 D. albipictus (8 larvae, 425 nymphs, 216 males and 284 females) were collected from moose, elk, horses, and cattle at 27 different locations in western Canada. Individual ticks were tested for the presence of Anaplasma and Ehrlichia DNA by nested or standard PCR. One engorged female was positive by PCR. Sequencing of part of the 16S rDNA gene indicate that the DNA was from an Ehrlichia species. Phylogenetic analysis using the neighbor-joining method showed there was strong statistical support for a clade comprising the Ehrlichia in D. albipictus and isolates of Ehrlichia minasensis from Brazil, China, Thailand, and Malaysia that were isolated from Rhipicephalus microplus. Based on the 16S rDNA sequence, DNA from this bacterial species was also detected in cattle from British Columbia, Canada. However, this organism was originally designated as Ehrlichia sp. BOV2010 and cross-reacted in serological tests, which has implications for diagnosis of bovine anaplasmosis.