Lyme disease is an illness caused by the bacterium Borrelia burgdorferi which is transmitted by an infected tick. In Northwestern Ontario there are several species of ticks. The Ixodes scapularis (blacklegged tick) species is primarily responsible for spreading tick-borne diseases to humans. The more common wood tick, is not known to be a disease vector.
Tick-borne diseases should be suspected when there is a known and probable tick exposure and when symptoms appear in accordance with timelines of the disease progression. It should be cautioned that patients may have no recollection of a tick bite because the bite is relatively painless and blacklegged ticks are very small, especially during the nymph stages. Exposure to blacklegged ticks can occur between April and December in northwestern Ontario. This is when outdoor air temperatures are consistently above 4°C and blacklegged ticks are active.
The incidence rate for Lyme disease in 2016 was 7.4 per 100,000 (6 cases) in the Northwestern Health Unit’s catchment area. In previous years, the number of cases were less and there was a 5-year average incidence rate of 1.2 cases per 100,000 per year. This is likely an underestimate as cases who are clinically diagnosed may not be reported to the health unit.
In Manitoba, the incidence rate for Lyme disease was 3.88 per
100,000 population in 2016. In Minnesota, the rate was 23.78 per 100,000 population in 2016.
Tick Surveillance and Estimated Risk Areas
Kenora and surrounding area is now considered an estimated risk area for Lyme disease in Ontario by Public Health Ontario. Estimated risk areas are locations where blacklegged ticks have been identified or are known to occur and where humans have the potential to come into contact with infected ticks. The Municipality of Rainy River and surrounding areas has been an estimated risk area since 2013.
2017 tick surveillance results results show that more than 20% of blacklegged ticks are positive for the bacterium that causes Lyme disease. Health care providers should consider prophylaxis for Lyme disease if a tick is attached for more than 24 hours and is from Kenora, Rainy River or the area surrounding these municipalities.
For more information:
Blacklegged Tick Risk Areas in Manitoba:
Removal of a blacklegged tick within 24 hours can prevent the transmission of B. burgdorferi. If a blacklegged tick is attached for longer than 24 hours, a health care provider can consider prophylaxis to prevent Lyme disease if the tick is likely from an area where tick infection rates are more than 20%; this includes Kenora, Rainy River or the areas surrounding these municipalities.
Reference: IDSA guidelines
|Prophylaxis can be offered if all of the following criteria are met:|
- The blacklegged tick is partially or fully engorged or was attached for 24 hours or more AND
- The blacklegged tick is likely from a region where tick infection rates for B. burgdorferi are more than 20% AND
- Doxycycline is not contraindicated
If a patient does not meet these criteria, they should be advised to monitor signs and symptoms for 30 days.
- Adults: Doxycycline 200mg orally * 1 dose;
- Children > 8 years: Doxycycline 4mg/kg, up to a maximum dose of 200mg
||Doxycycline is relatively contraindicated in pregnancy and for children < 8 years|
||Whether the patient receives prophylaxis or not, advise to monitor for signs and symptoms of Lyme disease for 30 days. If there are signs and symptoms, early treatment for Lyme disease may be indicated.|
Suspected and/or confirmed cases of Lyme disease, whether clinically diagnosed or laboratory confirmed, are reportable to local public health under the Health Protection and Promotion Act.
Tools and information for healthcare providers on diagnosing and testing:
What to tell patients to do with the tick if they bring it to your clinic:
Residents or visitors can bring ticks that are taken off of humans in to their local health unit office or submit a photo of the tick electronically using the NWHUConnect - Healthy Environments iOS app, to help with our passive surveillance program. Tick samples and photos are reviewed by a public health inspector. Blacklegged ticks or ticks that cannot be identified are sent to the lab for further testing. Wood (dog) ticks are not known to transmit tick borne disease and are not submitted to the lab for further testing. Test results are used for our surveillance only as it takes a significant time to receive them. These results are not used to guide patient treatment.
Key prevention messages for patients:
Follow these tips to avoid ticks:
- Wear light coloured clothing so ticks are easier to spot.
- Keep covered with long pants and a long-sleeved shirt.
- Wear closed footwear, socks, and tuck your pants into your socks.
- Use a tick repellant that has "DEET" (follow the manufacturer's directions).
- Put a tick and flea collar on your pets, and check them for ticks periodically.
- Search your body well for ticks after being in grass or bushy areas. Pay special attention to groin, scalp, and armpits. Use a mirror to check your back.
On your property:
- Mow the lawn regularly.
- Remove leaf litter, brush and weeds.
- Keep tree branches and shrubs trimmed to let in more sunlight.
- Move children's swing sets and sandboxes away from the wooded or bushy edges of a play area. Consider placing swing sets and sandboxes on a woodchip or mulch foundation.
- Ticks often attach themselves to rodents, deer and birds. Keep rodents away by sealing stone walls and small openings around the yard. Use plants that do not attract deer or consider fencing to keep deer out of the yard. If you have a bird feeder keep it away
What does the Health Unit do?
Public health's role is to measure and evaluate risk of tick-borne diseases. The health unit completes active and passive surveillance for ticks that can carry Lyme disease in our region. Individuals can bring any ticks found on humans to the health unit and it will be assessed and/or tested for Lyme disease. Surveillance data is used to track whether or not certain species of ticks are becoming more common to an area and to know if they are carrying Lyme disease.
The Northwestern Heath Unit also tracks suspected and/or medically confirmed cases of Lyme disease throughout the region and educates the public on ways to reduce the risk of getting Lyme disease.
For more information: