Black-Legged (Deer) Tick

Ixodes scapularis is the principal vector of Lyme disease in eastern and central North America. Adults are small (3-4 mm unfed; 11 mm fully engorged), reddish-brown with characteristic black legs. The lifecycle is two years long across three blood meals (larva, nymph, adult). Each life-stage feeds once on a vertebrate host: larvae prefer mice, nymphs prefer rodents and humans, adults prefer deer (hence 'deer tick'). When attached, the tick secretes a glue-like cement around the mouthparts that adheres her to the host for 3-7 days while she feeds. During the feed, ticks can transmit Borrelia burgdorferi (Lyme disease), Anaplasma phagocytophilum (anaplasmosis), Babesia microti (babesiosis), and Powassan virus. The CDC estimates 476,000 Lyme cases per year in the US — a tenfold increase from the 1990s. Climate change has expanded Ixodes scapularis range northward by approximately 50 km per decade since 1995. Canadian populations established in southern Ontario in the 2000s are now expanding into northern Quebec and the prairies.