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

The range of 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 and its associated pathogen, , in northwestern Ontario. We assessed five years of active and passive tick surveillance data in northwestern Ontario. Between 2013 and 2017, 251 were submitted through passive surveillance. The submission rate increased over time, and the proportion infected with was 13.5%. Active tick surveillance from 2014 to 2016 found few specimens. In 2017, 102 were found in 10 locations around the city of Kenora; 60% were infected with , eight tested positive for , and one for POWV. ticks were found in 14 locations within the Northwestern Health Unit area, with seven locations containing -positive ticks. We found abundant populations in the southern portion of northwestern Ontario and northward expansion is expected. It is recommended that populations continue to be monitored and mitigation strategies should be established for rural northern communities.