Urban Wildlife
Efforts to make Canadian cities more biodiverse and carbon-neutral are increasing our risk of Lyme disease. As spring returns (and with it black-legged ticks), here is what you need to know
Efforts to make Canadian cities more biodiverse and carbon-neutral are increasing our risk of Lyme disease. As spring returns, be prepared
In our globalized, urbanized and increasingly mobile century in which migration means populations are in a state of constant and rapid exchange, viruses spread farther faster too. Climate change only exacerbates the problem.
Almost 20 per cent of all infectious diseases worldwide are transmitted through host organisms, known as vectors, such as mosquitoes, midges, sandflies, aquatic snails, lice and ticks. The diseases they carry result in more than a million deaths worldwide each year. And while the greatest burden (of yellow fever, malaria, dengue, zika and chikungunya, among others) falls to the world’s poorest populations in tropical and subtropical climates, vector-borne disease is very much an issue in Canada as well.
Climate change, mobility and urbanization are all factors. The irony is that actions taken recently to improve urban ecology and reduce carbon output are contributing to a growing problem here. And while mosquitoes might seem the most threatening vector in this country (we have more of them within our boundaries than any other nation, and West Nile virus has been a threat since 2002, albeit a remote one for most) it is two distinct types of black-legged tick and the Lyme disease they distribute that Canadians should be watching. In 2009 there were 144 cases reported; in 2017, there were 2,025 cases. The culprits are the deer tick aka black-legged tick (Ixodes scapularis) in eastern and central regions of southern Canada and the somewhat less threatening western black-legged tick (Ixodes pacificus) in British Columbia.
Ticks need blood to live, and they get it by attaching themselves to other animals to feed. Once infected with the bacteria Borrelia burgdorferi from the blood of wild birds and rodents, they are capable of spreading Lyme disease with each subsequent feeding. Among the primary victims are humans and their pets, especially dogs.
Even if it is somewhat remote, the threat is real: the effects of Lyme disease can be devastating. Early symptoms, between three and 30 days after a tick bite, resemble those of a mild flu: fever, chills, headaches, joint and muscle pain, swollen lymph nodes and deadening fatigue. A tell-tale sign is a rash that often — but not always — looks like a bull’s eye. Untreated, worst-case scenarios might include Bell’s palsy (facial paralysis), heart disorders, neurological damage, meningitis, arthritis and other nasty conditions. So while infection risk might be moderate, the stakes are high.
Until recently, the only place in Canada where we had to take precautions was in the wilderness. No more. Black-legged ticks have begun moving into town. Climate change has helped, creating the warmer and wetter conditions that these parasites particularly enjoy. Migrating bird hosts, whose destinations have been altered by rising temperatures and the refuge offered by cities, are introducing the disease outside endemic areas.
The trend is deepened by strategies to contain urban sprawl, reduce pollution and minimize the heat island effect. With a goal of fostering biodiversity and becoming more “livable,” cities across the country are increasing urban density while augmenting green space and natural features, creating natural corridors to encourage greater biodiversity. Meanwhile, an increased emphasis on getting people outdoors and onto leafy urban hiking paths for a healthier urban lifestyle is exposing citizens to a greater risk of contracting Lyme disease.
The most effective response to the problem will not likely be found in high-level policy and planning strategies. Yes, we will need to adjust how we design and manage urban and suburban environments. But first, the now-familiar instructions will have to become routine, like wearing long sleeves and long pants when out in nature (the likelihood of fashion-conscious urbanites tucking their pants into their socks is probably a non-starter). And it will be a stretch to convince urban hikers to apply Deet-based insect repellent before heading to the park. But everyone out in urban nature should do a thorough check afterward for ticks, especially in the hair, around the ears, under arms, behind the knees, between the legs and around the waist. If you find a tick on your body, remove it completely with tweezers. Catching it within 24 hours will help prevent infection. Ticks can be hard to see when they first latch on—they can be as small as a poppy seed — but are much easier to find once they are engorged.
Similarly, the most effective community action will be local. Prevention will require the vigilance of everyone in a community, reporting pooling and stagnant water to the local municipality, changing yard design and maintenance, and using pesticides when required. Imagine a program like neighbourhood watch, engaging entire communities in minimizing the risk of Lyme disease. In the meantime, check out Health Canada’s advisories, as well as more localized information from your provincial and municipal government websites.
ACTIONS TAKEN RECENTLY TO IMPROVE URBAN ECOLOGY AND REDUCE CARBON OUTPUT ARE CONTRIBUTING TO A TICK PROBLEM THAT IS GROWING WORSE