Analysis of the human population bitten by Ixodes scapularis ticks in Quebec, Canada: Increasing risk of Lyme disease.

Ixodes scapularis, the main vector of Borrelia burgdorferi, the spirochetal agent of Lyme disease, is expanding its range in southern Canada and bringing risk to the public from Lyme disease. The aims of this study were to (i) describe how risk of Lyme disease in Quebec, Canada, has changed from 2008 to 2014 by analysis of the number of tick submissions, the geographic scope of ticks submitted and the prevalence of B. burgdorferi in ticks removed from people and submitted through the Quebec passive tick surveillance program and (ii) explore whether exposure to ticks is influenced by age and sex. Ticks were collected from 2008 to 2014 in a passive surveillance program conducted by the Laboratoire de santé publique du Québec (LSPQ), and tested by PCR for B. burgdorferi at the National Microbiology Laboratory. The number of ticks submitted each year more than quadrupled during the study period (from 174 in 2008 to 962 in 2014), increases in the geographic range and geographic uniformity of submissions amongst municipalities were observed, and infection prevalence in the ticks (mostly adult females) submitted rose from 5.9% in 2008 to 18.1% in 2014. These data are consistent with outcomes from active surveillance for blacklegged ticks. More men (54.4%) than women (45.6%) were bitten by I. scapularis ticks and the frequency of tick submission was highest in children under 15 years of age and in the adults 50-70 years old. These findings demonstrate the utility of conducting passive tick surveillance using humans and provides information on risk groups (i.e., males, children under 15, adults older than 50, and those living in the more southern parts of the province) to which information on personal protection and tick-bite prevention should be most strongly targeted.