Abstract
To summarize seven years of surveillance data for Lyme disease cases reported in Canada from 2009 to 2015. We describe the incidence over time, seasonal and geographic distribution, demographic and clinical characteristics of reported Lyme disease cases. Logistic regression was used to explore differences between age groups, sex and year to better understand potential demographic risk factors for the occurrence of Lyme disease. The number of reported Lyme disease cases increased more than six-fold, from 144 in 2009 to 917 in 2015, mainly due to an increase in infections acquired in Canada. Most locally acquired cases were reported between May and November. An increase in incidence of Lyme disease was observed in provinces from Manitoba eastwards. This is consistent with our knowledge of range expansion of the tick vectors in this region. In the western provinces the incidence has remained low and stable. All cases reported by Alberta, Saskatchewan and Newfoundland and Labrador were acquired outside of the province, either elsewhere in Canada or abroad. There was a bimodal distribution for Lyme disease by age with peaks at 5-9 and 45-74 years of age. The most common presenting symptom was a single erythema migrans rash (74.2%) and arthritis (35.7%). Variations in the frequency of reported clinical manifestations were observed among age groups and years of study. Lyme disease incidence continues to increase in Canada as does the geographic range of ticks that carry the Lyme disease bacteria. Ongoing surveillance, preventive strategies as well as early disease recognition and treatment will continue to minimize the impact of Lyme disease in Canada.
Highlights
Lyme disease, caused by the bacterium Borrelia burgdorferi sensu stricto in North America is transmitted to humans from wild animal reservoir hosts by Ixodes spp. ticks (1) in their woodland habitats (2)
Lyme disease risk in Canada occurs where tick vectors are established in southern British Columbia and in southern parts of central and eastern Canada into which the efficient tick vector I. scapularis is spreading from the United States, driving Lyme disease emergence in Canada (3)
In light of the documented northern migration of ticks into Canada, Lyme disease became nationally notifiable in Canada in 2009 and basic information on human cases is submitted by all provinces and territories to the National Notifiable Disease Surveillance System (NNDSS) coordinated by the Public Health Agency of Canada (PHAC)
Summary
Lyme disease, caused by the bacterium Borrelia burgdorferi sensu stricto in North America is transmitted to humans from wild animal reservoir hosts by Ixodes spp. ticks (1) in their woodland habitats (2). In light of the documented northern migration of ticks into Canada, Lyme disease became nationally notifiable in Canada in 2009 and basic information on human cases is submitted by all provinces and territories to the National Notifiable Disease Surveillance System (NNDSS) coordinated by the Public Health Agency of Canada (PHAC). A Lyme Disease Enhanced Surveillance (LDES) system was initiated by PHAC in 2010 with provincial public health organizations to obtain more detailed data on Lyme disease cases. Together, these surveillance systems aim to identify changing trends in Lyme disease incidence, the Canadian population at risk and the types of clinical disease in Canada to inform clinician-based Lyme disease diagnosis and reporting
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