Distribution of Ixodes scapularis in Northwestern Ontario: Results from Active and Passive Surveillance Activities in the Northwestern Health Unit Catchment Area

The range of Ixodes scapularis is expanding in Ontario, increasing the risk of Lyme disease. As an effective public health response requires accurate information on disease distribution and areas of risk, this study aims to establish the geographic distribution of I. scapularis and its associated pathogen, B. burgdorferi, in northwestern Ontario. We assessed five years of active and passive tick surveillance data in northwestern Ontario. Between 2013 and 2017, 251 I. scapularis were submitted through passive surveillance. The submission rate increased over time, and the proportion infected with B. burgdorferi was 13.5%. Active tick surveillance from 2014 to 2016 found few I. scapularis specimens. In 2017, 102 I. scapularis were found in 10 locations around the city of Kenora; 60% were infected with B. burgdorferi, eight tested positive for A. phagocytophilum, and one for POWV. I. scapularis ticks were found in 14 locations within the Northwestern Health Unit area, with seven locations containing B. burgdorferi-positive ticks. We found abundant I. scapularis populations in the southern portion of northwestern Ontario and northward expansion is expected. It is recommended that I. scapularis populations continue to be monitored and mitigation strategies should be established for rural northern communities.