Case Report: Anaplasmosis in Canada: Locally Acquired Anaplasma phagocytophilum Infection in Alberta

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.