Map of Simcoe Muskoka

Environment

Passive Tick Surveillance

When people find a tick on themselves or on other people, they are asked to submit the tick to the health unit for testing through Public Health Ontario. This is referred to as passive tick surveillance, and has been ongoing at Simcoe Muskoka District Health Unit since 2007. The passive tick surveillance program provides us with information on the type of ticks present thoughout Simcoe Muskoka communities and informs active surveillance (tick dragging) activities.

The purpose is to detect and monitor the presence of blacklegged ticks (Ixodes scapularis) that can or are carrying Borrelia burgdorferi, the bacteria that causes Lyme disease in humans. See the health unit’s page on Lyme disease and ticks for more information about protecting yourself from ticks and about submitting ticks to the health unit.

Between 2007 and 2018, 878 ticks were submitted to Simcoe Muskoka District Health Unit for testing. Tick submissions have increased over this time period with four ticks submitted in 2007 and 237 ticks submitted in 2017. The figure below shows that 42% of the ticks submitted to health unit between 2007 and 2018 were identified as blacklegged ticks. For more information on safely removing a tick, see the health unit’s fact sheet on Lyme disease.

191127TickSubmissionType_2007to2018

Of the blacklegged ticks submitted to the health unit, the majority (71%) of these ticks were acquired locally, 21% were acquired outside of Simcoe Muskoka, and for 8% of ticks submitted, we’re not sure where the tick was acquired. This means that over two-thirds of the blacklegged tick submissions to the health unit resulted from outdoor activity within the Simcoe Muskoka region.

The graph below shows that 16 locally acquired blacklegged ticks have tested positive for the bacteria that causes Lyme disease (Borrelia burgodorferi): one in 2012, one in 2015, three in 2016, eight in 2017 and another three in 2018.

Eighteen additional blacklegged ticks that were submitted to the health unit tested positive for B. burgodorferi in 2014 through 2018: fourteen were acquired in Ontario outside of Simcoe Muskoka, one in the United States, and three had unknown acquisition locations.

From 2007 to 2018, 43% of locally acquired ticks submitted to the health unit were blacklegged ticks. This proportion has varied from 0% in 2008, to 62% in 2018. This suggests that the number of blacklegged ticks in our local environment is growing.

SMDHUPassiveTickSurv_Annual_2007to2018

Technical Notes

The objective of passive tick surveillance is to understand the risk of Lyme disease infection and includes identifying locations with multiple tick submissions over multiple years. It should be noted that ticks submitted to Simcoe Muskoka District Health Unit are used to help determine areas of risk, and not for the purpose of Lyme disease diagnosis in patients.

An endemic area is defined as an area in which a reproducing population of Ixodes scapularis or Ixodes pacificus tick vectors is known to occur, which has been demonstrated by molecular methods to support transmission of B. burgdorferi at that site (source: Public Health Ontario Lyme Disease Case Definition).

A risk area is defined as a location where at least one blacklegged tick was found during three person-hours of drag sampling at a location, between May and October. To warrant tick drag sampling, passive surveillance indicators and suitable conditions to support populations of blacklegged ticks must be present. Passive surveillance indicators may include, but are not limited to, information about ticks submitted for identification and/or testing for the Lyme disease bacteria, assessment of exposure information from locally acquired human Lyme disease cases, and information from health care professionals. In new locations with no history of blacklegged tick populations, it would be expected that tick dragging be conducted at two different times (spring and fall) to confirm the presence of the blacklegged tick. For location of risk areas, please see the Public Health Ontario Risk map.