Lyme Disease in Canada

Here, we document a case of domestically acquired human granulocytic anaplasmosis in Ontario. This disease is a tick-borne infection of neutrophils caused by A. phagocytophilum. The bacterium is most commonly transmitted by bites from the blacklegged tick, Ixodes scapularis. The first cases of human granulocytic anaplasmosis were reported in Minnesota and Wisconsin in 1994. From 2008 to 2012, the mean reported annual incidence in the United States was 6.3 cases per million.1 The first case of human granulocytic anaplasmosis that originated in Canada was reported in 2009.2 Since then, further cases have been documented in Manitoba, the only province for which it is a reportable disease. Since cases began to be tracked in January 2015, 21 have been reported, 17 of which were in 2016. A US case series of 42 cases of human granulocytic anaplasmosis found a mortality of 4.9%.3