Search

ABSTRACT 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 and 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 and 2019 ( p  = 0.02), with a corresponding increase in the 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.

Human granulocytic anaplasmosis is an obligate intra-granulocytic parasite that is transmitted by Ixodes scapularis and Ixodes pacificus in North America. We report on the second laboratory-confirmed case of Anaplasma phagocytophilum acquired within the province of Alberta, Canada. A 67-year-old woman from the Edmonton health zone developed nonspecific systemic symptoms including fatigue, night sweats, myalgia, headaches, and fever 6 days after noticing a tick on her left upper arm in May of 2017 (day 0). On day 13, she was found to have thrombocytopenia. Her symptoms progressed until day 16 when she was treated empirically with doxycycline, at which time she slowly improved over the subsequent 2 months. The tick was later identified as a partially engorged female blacklegged tick, I. scapularis , and it was positive for A. phagocytophilum DNA by PCR. Anaplasma serology performed retrospectively on blood samples collected on days 13, 31, and 52 showed a greater than 4-fold increase in A. phagocytophilum (IgG titers from less than 1:64 on day 13 to 1:2048 on days 31 and 52), consistent with an acute infection. Although populations of blacklegged ticks are not yet established in Alberta, suspicion should remain for tick-borne diseases because infected ticks are introduced into the province by migrating birds. This case report highlights the need to remind physicians and other public health professionals that rare, non-endemic tick-borne diseases can occasionally occur in low-risk jurisdictions.