Reducing tick-related risks through improved design and maintenance in outdoor environments

Ticks are a growing public health concern in Canada due to several interrelated factors. They are capable of infecting humans with pathogens that can cause illness and they can be found in many terrestrial environments. The number of environments in Canada where ticks can survive and thrive is expanding due to global warming, land fragmentation (through deforestation and urbanization, and changing animal migration patterns.  The range of ticks is predicted to expand 35-55km per year northwards from their current habitats.

Ticks are small, slow-moving arthropods with three life stages: larvae (size of a grain of sand), nymph (size of a poppy seed), and adult (size of an apple seed).  At every life stage, ticks require a blood meal from mammals, birds, reptiles, or amphibians.  This enables them to transition to the next life cycle stage. It is during this blood meal that a tick can transmit pathogens to humans (and other species). 

Ticks are known to carry bacterial, viral, and protozoan pathogens capable of infecting humans.  In Canada, the predominant tickborne infections are Lyme disease (Borrelia burgdorferi), anaplasmosis (Anaplasma phagocytophilum), babesiosis (Babesia microti), Borrelia miyamotoi disease, Rocky Mountain spotted fever (Rickettsia rickettsii), Powassan virus disease, and tularemia. There are several other emerging tick-related pathogens of concern in North America, including alpha-gal syndrome (allergy specific to red meat), Ehrlichiosis (Ehrlichia chaffeensis), Heartland virus, tick-borne encephalitis, and toxoplasmosis (Toxoplasmosis gondii). Many of these pathogens are not nationally reported, as such the true magnitude of infection is unknown and likely underrepresented by public health surveillance efforts.  This highlights the importance of being vigilant of all tick bites and subsequent symptoms regardless of the tick vector species.

The risk of human exposure is proportional to the time spent outdoors in tick habitats (tall grass, brush, shrubs, and leaf litter).  Research shows that individuals at greatest risk of exposure to ticks are those who spend the most time outdoors: children 5-14 years, adults 55-79, and males. Activities such as hiking, camping, gardening, walking your dog, or occupational activities such as landscaping or tree planting can increase exposure to ticks.

This blog summarizes the key messages from a series of NCCEH evidence-based reviews, a  fact sheet, and an accompanying webinar examining tick-related risks in parks and recreational areas. The goal is to provide easy-to-use, accurate information on how to minimize the risk of tick encounters across parks, recreational areas, and residential properties.  

Where can ticks be found?

There are over 40 tick species found in Canada.  Not all ticks transmit pathogens to humans.  The primary vectors of concern are: blacklegged tick (Ixodes scapularis), western blacklegged tick (Ixodes pacificus), American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), and Lone Star tick (Amblyomma americanum).  These species have all been identified in Canada.

Ticks can be found in many terrestrial environments across Canada.  Blacklegged ticks (Ixodes scapularis) and Western blacklegged ticks (Ixodes pacificus) prefer high moisture areas and can often be found in leaf litter and under the forest canopy.  American dog ticks (Dermacentor variabilis), and Rocky Mountain wood ticks (Dermacentor andersoni) prefer drier environments and are often found in grass and shrubs.  Lastly, Lone Star ticks (Amblyomma americanum) are often found in wooded areas and in leaf litter.

The range of ticks is rapidly increasing due to climate change and land use changes. Tick population changes are primarily being driven by increasing ambient temperatures (due to climate change) which can increase maturation and decrease the lifespan of ticks.  Forest fragmentation and land use changes (land fragmentation through deforestation and urbanization of natural continuous forests into smaller sections) also plays an important role as it can increase tick density by facilitating host population (e.g., deer and rodents) movement into new areas.

When are ticks active?

The risk of tick exposure is greatest when ticks are actively seeking a blood meal, in the spring and early summer (May and July) and again in the fall (September and November). It’s important to note that different tick species have varying life cycles, which can increase the likelihood of exposure at different times of the year.  Ticks can also survive winter months by being insulated under tree litter, brush, and snow.  If the temperature is above 4 degrees Celsius, ticks can be active.  

How can we reduce the risk of tick encounters?

A combination of personal protective behaviours and landscape design and management practices are found to be effective in reducing the risk of tick encounters.

Personal protective behaviours:

Individuals can minimize their risk of acquiring a tick-borne pathogen by engaging in preventive behaviours both when recreating outdoors and when back inside.  This fact sheet provides a checklist of preventive behaviours to reduce the likelihood of tick bites and pathogen transmission.  

Landscape design and management practices

Tick populations can be managed through principles of integrated pest management by adopting deliberate landscape design and active management practices.  Such design principles primarily include: 1) plant selection to deter animal hosts and ticks, 2) plant, lawn, and property maintenance to reduce density and limit tick habitats by increasing sun exposure and decreasing humidity to desiccate ticks and 3) the use of fencing and hardscaping (gravel, stone, bare soil, and cedar chips) to limit wildlife access and habitats.  This fact sheet provides a detailed list and figure of landscape design practices to minimize tick habitats.  

Summary

With the increasing geographic range of ticks throughout North America, it is becoming increasingly important to limit human encounters to both ticks and potential tick-borne infections.  There is no simple solution.  Active tick management requires cross-sectoral collaboration to facilitate individual vigilance and pro-activeness, management of recreational and residential properties, continued support and funding of public health research initiatives, surveillance, and land-use practices that minimize tick-related risks. 

Tick-related risks must be communicated across populations to increase awareness.  This will help individuals know what ticks look like, where they are likely to be found, how best to manage landscaped environments, and what to do in the event of a tick bite.  Innovative approaches to communicate tick-related risks include: Tick Talk (aimed at educating 5-10 year old children) and Spray Safe, Play Safe (series of short films providing information on how to manage risks in your backyard).  Smartphone applications and web-based platforms, such as e-tick, identify ticks and provide real-time citizen science generated data to help supplement public health surveillance efforts.  Artificial intelligence may also have a role to play in identifying tick species in real-time.

To support these risk communication efforts, the NCCEH has designed an easy-to-reference fact sheet on ticks in a changing environment.  The 4-page resource provides easily accessible information on: ticks and their habitats, how to design and manage outdoor environments to minimize ticks, and how to reduce one’s own risk of tick encounters outdoors.  It is intended for parks and recreational properties professions, landscape designers, grounds maintenance personnel of residential properties, as well as users of outdoor environments. To facilitate use and sharing across users and organizations, the fact sheet can be downloaded as a package or as individual stand-alone pieces.

Author

Dr. Negar Elmieh is an interdisciplinary researcher, educator, and advocate for health and environmental issues.