Multi-Scale Clustering of Lyme Disease Risk at the Expanding Leading Edge of the Range of Ixodes scapularis in Canada

Abstract

Since its detection in Canada in the early 1990s, Ixodes scapularis, the primary tick vector of Lyme disease in eastern North America, has continued to expand northward. Estimates of the tick’s broad-scale distribution are useful for tracking the extent of the Lyme disease risk zone; however, tick distribution may vary widely within this zone. Here, we investigated I. scapularis nymph distribution at three spatial scales across the Lyme disease emergence zone in southern Quebec, Canada. We collected ticks and compared the nymph densities among different woodlands and different plots and transects within the same woodland. Hot spot analysis highlighted significant nymph clustering at each spatial scale. In regression models, nymph abundance was associated with litter depth, humidity, and elevation, which contribute to a suitable habitat for ticks, but also with the distance from the trail and the type of trail, which could be linked to host distribution and human disturbance. Accounting for this heterogeneous nymph distribution at a fine spatial scale could help improve Lyme disease management strategies but also help people to understand the risk variation around them and to adopt appropriate behaviors, such as staying on the trail in infested parks to limit their exposure to the vector and associated pathogens.

Species distribution models for the eastern blacklegged tick, Ixodes scapularis, and the Lyme disease pathogen, Borrelia burgdorferi, in Ontario, Canada

“…Recent studies have also focused on microclimate or microhabitat to identify I. scapularis distributions at a local scale, and have found significant associations between nymphal and adult tick densities with forest type, forest understory, dominant tree type, depth of litter layer, distance from trails, type of trails, and distance to roads, which support our findings for the dominance of forests in I. scapularis habitat suitability [15,21,22,57]. A local ecological niche model for I. scapularis in the city of Ottawa also found that distance to forests and treed land were among the strongest variables predicting the distribution of blacklegged ticks [24].…”

“…The risk of contracting Lyme disease depends on several factors including human activity and behaviours as well as the density of B. burgdorferi infected ticks in the environment, which is determined by both the abundance of I. scapularis and the proportion of ticks infected with B. burgdorferi [11][12][13][14]. The most common method used for estimating risk of exposure to B. burgdorferi is the identification of I. scapularis populations in the environment using various surveillance methods [15]. In Canada, the spatial distribution of I. scapularis ticks has been studied via passive tick surveillance programs that rely on tick submissions from the public and healthcare providers, and by active tick surveillance that utilizes mainly drag sampling techniques to sample the environment for questing ticks [16].…”

“…burgdorferi is the identification of I . scapularis populations in the environment using various surveillance methods [ 15 ]. In Canada, the spatial distribution of I .…”

Utilisation des images d'observation de la terre pour améliorer la cartographie des risques de maladies associées au changement climatiques

“…Historiquement, les changements dans la répartition de divers types d'habitats et des espèces hôtes ont été accompagnés de changements dans la répartition et l'abondance des tiques (55). Les DEC des maladies transmises par les tiques comprennent le type et la densité du couvert forestier et le degré de fragmentation de la forêt, ainsi que les conditions de température et d'humidité prévalant dans les habitats forestiers (12,13,17,(56)(57)(58)(59)(60)(61)(62)(63).…”

Public perceptions of Lyme disease and climate change in southern Manitoba, Canada: Making a case for strategic decoupling of climate and health messages

“…While active and passive surveillance efforts are ongoing to monitor the environmental risk of Lyme disease in Manitoba and across Canada (e.g. [34,36,37]), experts looking to communicate the risks of emerging disease dynamics are seeking better understanding of public knowledge on Lyme disease. Understanding public risk perception can help target Lyme disease communications and drive the adoption of preventative behaviours [35,38].…”