Epidemiology of Ticks Submitted from Human Hosts in Alberta, Canada (2000-2019)

The geographic range and occurrence of tick species is dynamic. This has important public health implications due to important tick species that can transmit pathogens. This study presents a retrospective review of tick genera recovered from humans and submitted for identification in Alberta, Canada, over a 19-year period. The total number of ticks and proportion of genera were analyzed over time. Molecular testing for a number of pathogens associated with and was conducted. A total of 2,358 ticks were submitted between 2000 and 2019, with 98.6% being acquired in Alberta. The number of ticks submitted increased significantly over time (< 0.0001). ticks were the most abundant genus, followed by and . There was a significant decrease in the proportion of ticks between 2013 and 2019 (= 0.02), with a corresponding increase in the proportion of ticks over the same time (= 0.04). No statistically significant change in seasonality was identified. was detected in 8/76 (10.5%; 95% CI 5.4-19.4%) of all and ticks submitted. This translated to a positivity of 0.35% (95% CI 0.15-0.68%) among all ticks received. species (especially ) remains the most common tick feeding on humans in Alberta. Small numbers of vector species (including ) are encountered annually over widely separated geographic areas in the province. The risk of exposure to tick-borne pathogens (e.g. Lyme disease) in Alberta remains low.