Epidemiology of ticks submitted from human hosts in Alberta, Canada (2000-2019)

TitleEpidemiology of ticks submitted from human hosts in Alberta, Canada (2000-2019)
Publication TypeJournal Article
Year of Publication2022
JournalEmerg Microbes Infect
Start Page1
Date Published01/2022
AuthorsKanji JN, Isaac A, Gregson D, Mierzejewski M, Shpeley D, Tomlin P, Groechel M, Lindsay LR, Lachance L, Kowalewska-Grochowska K
Keywordsalberta, borrelia burgdorferi, dermacentor, ixodes, lyme, tick

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 Ixodes scapularis and I. pacificus was conducted. A total of 2,358 ticks were submitted between 2000-2019, with 98.6% being acquired in Alberta. The number of ticks submitted increased significantly over time (p<0.0001). Dermacentor ticks were the most abundant genus, followed by Ixodes and Amblyomma. There was a significant decrease in the proportion of Dermacentor ticks between 2013-2019 (p=0.02) with a corresponding increase in proportion of Ixodes ticks over the same time (p=0.04). No statistically significant change in seasonality was identified. Borrelia burgdorferi was detected in 8/76 (10.5%; 95% CI 5.4-19.4%) of all I. scapularis and I. pacificus ticks submitted. This translated to a B. burgdorferi positivity of 0.35% (95% CI 0.15-0.68%) among all ticks received. Dermacentor species (especially D. andersoni) remains the most common tick feeding on humans in Alberta. Small numbers of vector species (including I. scapularis/pacificus) 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.