Highlights
In Quebec, Lyme disease has been a reportable disease since 2003 and as of 2015, it is subject to integrated surveillance, including human surveillance and acarological surveillance (passive and active). This report presents an epidemiological portrait of Lyme disease in Quebec for the period from 2006 to 2019.
The data analysis revealed the following findings:
Human supervision
- Lyme disease is present in Quebec, but concentrated in the south of the province, particularly in Estrie and Montérégie.
- In Estrie, the risk is particularly present in the west of the region. Two territories of the Local Services Network (La Pommeraie and Haute-Yamaska) stand out with the highest incidence rates in the province, approaching those of the most endemic American states for Lyme disease. These two territories also stand out with a strong increase in the incidence rate over time.
- Montérégie is the second region most affected by Lyme disease in Quebec. Unlike Estrie, the risk is very dispersed in Montérégie with several municipalities endemic for Lyme disease.
- The geographical progression observed over time suggests that the risk of acquiring Lyme disease is constantly changing in Quebec. This is the case, for example, of southwestern Outaouais and Mauricie and Center-du-Québec, which have recorded an increase in the number of cases, with a few endemic municipalities during the last years of the study.
- Lyme disease is more common in men, young people under the age of 15 and people aged 60-69. It would therefore be important for public health authorities to target high-risk groups more to increase their vigilance and better direct preventive strategies.
- The seasonality of Lyme disease cases observed in Quebec reflects the period of tick activity Ixodes scapularis (I. scapularis) (main vector of the disease in Quebec) between the months of April and November, combined with a higher frequency of outdoor human activities during this period.
- The fact that the onset of symptoms in cases may occur outside of this risk period should be considered by healthcare professionals, who should not rule out the diagnosis of Lyme disease in the presence of compatible clinical manifestations.
Passive acarological monitoring
- Passive surveillance data is available for the period from 2009 to 2019. These data indicate that the number of ticks I. scapularis taken from humans is growing and expanding geographically in Quebec, with a temporal evolution similar to that of human cases.
- Western Estrie stood out for the high number ofI. scapularis of human origin, as well as a greater increase in the rate of tick submission per 100,000 inhabitants. The prevalence of Borrelia burgdorferi (B. burgdorferi) (the pathogen that causes Lyme disease in North America) in human ticks was also higher in this area, reflecting the elevated risk in human cases.
- The southwest of the Outaouais also stood out with a significant increase in the number ofI. scapularis of human origin submitted during the last years of the study.
Active acarological monitoring
- Active surveillance data is available for the period from 2010 to 2019. During this period, I. scapularis were collected in nearly half of the sites visited. The presence of the three stages of development of the tick (larva, nymph and adult) in the same year, indicating the establishment of the tick on a territory, was documented in 9% of the sites and the presence of B. burgdorferi was documented in 12% of the sites visited.
- The average tick density (nymphs and adults) was estimated at the main sites sampled between 2015 and 2019. Tick density varied widely between sites. This variation depends, among other things, on the choice of the location of the sites and the time of collection.
- Core sites located in endemic areas for Lyme disease had mean tick densities (nymphs and adults) and mean tick densities positive for Lyme disease. B. burgdorferi the highest.
Other pathogens transmitted by I. scapularis
- Pathogens responsible for other diseases also transmitted by I. scapularis are present in Quebec. An increase in the proportion of ticks infected with these pathogens is possible and should follow the establishment of tick populations I. scapularis.
- Data from passive and active acarological surveillance show thatAnaplasma phagocytophilum and to a lesser extent, Babesia microtifollow the temporal distribution of B. burgdorferi.
- Throughout the study period, a few positive ticks to Borrelia miyamotoi were detected and no ticks positive for the virus of Powassan has not been reported.
