Two researchers have designed a Lyme disease risk map in Estrie that takes into account the number of infected ticks in an area and the preventive behaviors adopted by the population, an element rarely taken into account in risk maps.
Among the 20 municipalities most at risk, 18 are in the Haute-Yamaska and Pommeraie local service networks. Sherbrooke, Bromont, Cowansville, Granby and Sutton are on this list.
“We are in forest massifs, neighborhoods [de résidences] on the mountainside. This geography means that people are not only exposed when they go out to parks, but also at home, in their backyards. We talk about “peridomestic”, that is to say that there are a lot of exhibitions around the house”, explains Catherine Bouchard, co-designer of the map and professor at the Faculty of Veterinary Medicine of the Montreal university.
Preventative behaviors – using DEET-based insect repellent, taking a bath or shower, and examining your body after visiting a high-risk area, in particular – are particularly important. “It can make THE difference”, underlines Cécile Aenishaenslin, co-author of the research, who recalls that a tick bite does not automatically give Lyme disease.
Transmission risk
“When we talk about Lyme disease, the tick [infectée] must remain attached for more than 24 hours for the risk of transmission of the bacteria to be significant. It’s not impossible that she transmits it before, but the longer she stays attached, the greater the likelihood that she will transmit the infection to you. Below 24 hours, the risk is minimal, “says the DD Aenishaenslin.
In Bromont, 12 to 13% of ticks are infected. If a tick remains attached for just over 24 hours, pharmacies in high-risk areas can prescribe preventive treatment within 72 hours of a bite.
By scrutinizing the prevention measures adopted by 10,000 people who participated in the study, the researchers found that the environments where there are the highest densities of ticks are not necessarily the places where the transmission rates of the disease of Lyme are the highest. It also depends on whether the means of prevention are applied.
For Public Health and municipalities
The Dres Bouchard and Aenishaenslin therefore designed their map for Public Health and municipalities so that they could carry out awareness campaigns among the population or to try to eliminate ticks from the environment, for example.
“If you are in an area with a high population density, there are a lot of ticks, but the behavior is less good, it becomes a priority to carry out interventions”, explains the DD Bouchard, who is also a veterinary epidemiologist with the Public Health Agency of Canada.
Currently, municipalities can cut tall grass along the most popular trails to reduce the risk of transmission of Lyme disease. They can also put up posters to warn people about the presence of ticks in parks and forests.
“Towns like Bromont are already doing it, says the DD Aenishaenslin. These are posters a bit like the ones you see for ragweed. If we see one of its signs, we know it, we will stay in the middle of the path and we will not let our children play in the dead leaves. »