Life After Lyme Disease

Image of adult blacklegged tick

Lyme disease is a tick-borne infection, and is primarily spread to humans through bites from deer ticks, Western blacklegged ticks and possibly lone star ticks.  These tick species carry the Borrelia burgdorferi bacterium which causes Lyme disease, and feed on a number of small to medium size mammals and birds including small rodents, deer and household pets.

Birds

Birds play a major role in the spread of Lyme disease as they can pick up a tick carrying the Borrelia burgdorferi bacterium in one location, and because it takes a long time for ticks to feed they could be hundreds or even thousands of miles away before the tick finally drops off.  The seasonal migration of birds in Northern America is key to the spread of Lyme disease and over 650 species of bird migrate to different parts of the world annually, either taking part in long distance migration to places such as Africa, Eastern Europe and South America, or short distance migration of just a few hundred miles.  Many birds such as White-throated Sparrows and robins spend the winter in Northern America before moving on to summer feeding grounds in Canada, and there are also a number of transitory birds that pass through Canada as a stop over on the way to other feeding grounds, and many of these could potentially be carrying infected ticks or the Borrelia burgdorferi bacterium itself, which they could pass on to uninfected ticks in the areas they feed in.

The spread of ticks carrying Borrelia burgdorferi bacterium into Southern Canada

Reforestation

A number of factors can influence the spread of any insect species, but the main culprit for the spread of ticks is thought to be reforestation.  Ticks are hardy creatures, but they do require the right habitats to live in. For example the blacklegged tick thrives in cool, moist conditions and the majority can be found in forested areas with dense shrub layers to provide shade and moisture, and tend to condense along the forest and woodland edges, where food is most abundant.  They can also survive in denser underground planting in some landscaped residential areas.

In recent years many areas that were previous cleared for farmland in northern America have been reverted back to small patches of woodland and forest, creating ideal environments not just for ticks, but for the animals they feed on such as deer and small rodents.  This increase in wild tick populations would not normally be a major problem but as urbanization is also increasing, with residential developments encroaching on wild areas, more and more infected ticks are coming into contact with humans, and these woodland border areas in which ticks are prevalent are now coexisting alongside residential areas, creating high risk zones for Lyme disease crossing to humans.

Reforestation is thought to be having a significant impact on the increasing spread of Lyme disease from North America into Canada, and studies by the Public Health Agency of Canada have so far tracked new infected tick emergence in Ontario, Nova Scotia, New Brunswick, Quebec and Manitoba. 

Steps to Prevent the Spread

The Public Health Agency of Canada and other organizations are calling for national surveillance to be put in place to monitor the changing patterns of tick behavior, to identify new endemic areas quickly and effectively in order to notify the public and local health authorities and ensure education is put in place to minimize the impact of Lyme disease.  Doctors are now required to report any suspected and confirmed cases of Lyme disease to the Public Health Agency, and this enhanced surveillance combined with greater physician and public awareness are crucial steps to help mimize the impact of the disease as it spreads into Canada.