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

Abstract

The American dog tick, Dermacentorvariabilis, is a tick of public and veterinary health importance in North America. Using passive tick surveillance data, we document distribution changes for the American dog tick in Ontario, Canada, from 2010 through 2018. Dermacentorvariabilis submissions from the public were geocoded and aggregated—from large to small administrative geographies—by health region, public health unit (PHU) and Forward Sortation Area (FSA). PHU hot spots with high rates of D. variabilis submissions were (1) Brant County, Haldimand-Norfolk and Niagara Regional in the Central West region and (2) Lambton and Winsor-Essex County in the South West region. The number of established D. variabilis populations with ≥ 6 submissions per year increased significantly during the study at regional (PHUs: 22 to 31) and local (FSAs: 27 to 91) scales. The range of D. variabilis increased similarly to the positive control (Ixodesscapularis) during the study and in contrast to the static range of the negative control (Ixodescookei). Submission hot spots were in warmer, low elevation areas with poorly drained soils, compared to the province’s low submission areas. Dermacentorvariabilis is spreading in Ontario and continued research into their vector ecology is required to assess medicoveterinary health risks.