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With spring comes the bright sun, the warm weather – and the ticks.
Ticks and some pests can carry bacteria, viruses and parasites that can cause diseases in humans. One in particular, the blacklegged deer tick (Ixodes scapularis), is known for its ability to transmit the bacteria causing Lyme disease, Borrelia burgdorferi .
Most of the time, these ticks are inactive during the winter and start looking for their next meal as the seasonal temperatures warm up. But as the global climate warms, it is more likely that some ticks will remain active during warmer winters and will be able to expand their habitats into new areas.
For this reason, hikers and dog owners must monitor ticks all year round to reduce the risk of illness.
Adapted to cold
Ticks and other pests are prevalent in the forests during the warmest months, from spring to autumn. But where do they go during the winter and how do they survive cold polar vortexes, inches of snow and chilling frostbite?
The animals use various strategies to cope with the winter months. While humans cover their clothes and generally avoid going outside in cold weather, other organisms resort to sophisticated behavioral adaptations and biological technologies to cope with the winter.
For Culex pipiens, the common domestic mosquito, hibernation is the key to survival. The insect enters a dormant phase (called diapause) that allows it to remain inactive during the winter. The female Culex mosquito, possibly carrying West Nile virus, accumulates fat in summer and autumn which serves as a reserve of energy and insulation during the winter months. This energy source is useful for mosquitoes looking for and settling in the artificial structures, sewers and burrows of the animals they use as shelter to help them escape subzero temperatures.
Ticks, however, do not enter diapause and are still able to bite and eat a blood meal in the right conditions. These blood-sucking parasites live close to their host organisms and can sometimes spend their entire life cycle on a single animal. They use a technique called a quest to find a host that will serve as their next blood meal. Ticks are positioned on the vegetation, such as tall grass, and assume a sitting position. This allows them to catch all the warm-blooded creatures that pass by.
Humans have used our own behavioral strategies to protect us from ticks during the hot seasons of the year. We do this by wearing long-sleeved clothing and using protective sprays when hiking in wooded and grassy areas.
Fight against the bite
One of the major challenges we still face in our fight against the bite is that ticks adapt their behavior more according to their geographic location in North America.
For example, blacklegged deer ticks will avoid quests in warmer southern regions, such as South Carolina, where the risk of dehydration pushes them to the ground, mainly under leaf litter. In contrast, northern tick populations are less threatened by desiccation due to wet conditions and are more likely to complete quests.
It is interesting to note that blacklegged deer ticks also have the ability to search at temperatures as low as minus 0.6 degrees Celsius (about 31 Fahrenheit). This means that deer ticks are not limited to looking for hosts during warmer months, but can continue to feed until early and late winter. It is important not to let your guard down when you enjoy the outdoors in winter.
Ticks are most active when temperatures exceed 7 degrees Celsius (around 45 Fahrenheit). But we must not believe that ticks die simply when the rigors of winter are unleashed. Deer ticks will probably survive, even the hardest polar vortex.
It is quite common for ticks to congregate in hibernation nests and seek refuge under the soil layer and plant waste in forests, where the temperature is less likely to fall below freezing. In addition, snow cover, which acts as an insulating blanket on ground litter, tends to further isolate ticks from freezing temperatures in the winter air.
Like other cold-tolerant organisms, ticks can also produce antifreeze protein that helps them tolerate colder temperatures by preventing their blood and tissues from freezing.
A future of climate change
Climate change and global warming have resulted in an increase in black-headed deer tick populations in more northern parts of North America, including the states of Wisconsin and New York, as well as in the United States. provinces of Ontario and Quebec.
Using climate change models and the current distribution of ticks, we can now predict the impact of future climate change on tick migration and potential health risks for these populations in Canada and Canada. in the USA. For example, the geographic distribution of the blacklegged tick is expected to spread to cover most of Atlantic Canada and Manitoba by 2070.
It is likely that all seasons are a tick season in some areas. It is therefore particularly important to remain alert to spot and avoid these tiny pests, even during a winter walk. For example, if your dog disrupts an intertwined tick of deer, he could bring unwanted guests home.
So what can we expect when the weather warms up and the long winter nights turn into sunnier spring days? You can be sure that a large number of ticks from last season have probably survived this winter. They are just waiting for the right benchmarks – warmer temperatures and longer hours of light – to emerge and begin their quest for the next blood meal.
Rosa da Silva is an Assistant Professor of Biology at the School of Interdisciplinary Science at McMaster University. This article was originally published on theconversation.com.
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