American dog ticks along their expanding range edge in Ontario, Canada

This study uses passive surveillance data collected between 2010 and 2018 to help determine where American dog ticks (Dermacentor variabilis) populations had their greatest concentrations in Ontario and where they were spreading. During that nine year period, more than 17,000 American dog ticks were collected by public health units, making this tick species the second most common in the province. (With over 22,000 specimens collected during the same time period, blacklegged ticks (Ixodes scapularis) ranked first).

In general, American dog ticks were more prevalent in warm, low-lying sites with poorly drained soil. The highest concentrations were found in the Central West (Brant, Haldimand-Norfolk, Niagara) and the South West (Lambton, Windsor-Essex) regions. The fastest growing populations were documented in the North East with Algoma seeing a staggering 50% annual increase. Large increases were also recorded in the North West region, most notably around Sault Ste. Marie.

Due to the availability of a large number of natural hosts for American dog ticks, researchers believe that environmental and/or climate factors play the biggest role in where and how fast this tick species can expand its range. However, this study does not try to pin down the factors propelling range expansion.

American dog ticks are known to cause several ailments that impact human health, including tularemia, Rocky Mountain spotted fever, and tick paralysis.