Those of you who live in the British Columbia Interior are likely already familiar with Rocky Mountain wood ticks (Dermacentor andersoni). They are the single most common tick species in the dry grassland ecosystems of the southern interior region and there are springs when the adults are so ubiquitous that recreating in the great outdoors is often followed by a de-ticking session, especially if Fido recreated with you.
Although more typically associated with central and eastern Canada, American dog ticks (Dermacentor variabilis) are also occasionally found in the Interior region. Until recently, these western populations were referred to as Western Dermacentor variabilis. That was until a 2021 study by Ohio State University researchers determined that these western populations are genetically distinct from their more easterly cousins and reclassified them as Dermacentor similis.
In 2019, the Canadian Pet Tick Survey (CPTS) launched a tick study during which participating clinics from across Canada submitted all of the ticks they collected from companion animals over a one year period that ran from April 2019 to March 2020. Typically, the majority of ticks received from BC during these sorts of studies are Rocky Mountain wood ticks. They are, after all, the province's most ubiquitous tick species. This study was different. The majority of submitted ticks were instead Dermacentor similis, all of which had been collected in the Okanagan and the area surrounding Kamloops.
It was an unexpected result and one that suggested that not only had Dermacentor similis ticks become established in the province, their numbers could actually rival Rocky Mountain wood ticks in some areas of the province.
A later study conducted at 33 sites across southern British Columbia between April 29 and May 23rd, 2022 failed to confirm the establishment of Dermacentor similis populations in the province. Most of those sites were located in southwestern and south-central BC although a handful were in the Kootenay-Boundary region. Ticks were collected by dragging for them during a time period that coincided with peak activity for Rocky Mountain wood ticks.
No Dermacentor similis ticks were found for reasons researchers couldn't explain. Possibly the timing had been off. Maybe Dermacentor similis ticks hit peak activity at a different time than Rocky Mountain wood ticks. Maybe they haven't yet become established in the province and the results of the earlier study had been a fluke. Maybe dragging had been an ineffective way to collect this type of tick and collecting small mammals might have yielded a different result. Maybe weather had been a factor.
Clearly, further studies are needed to confirm whether or not Dermacentor similis has become established in BC and how its populations compare to that of the Rocky Mountain wood tick.
