As a medical entomologist and the Department of Defense’s senior scientific adviser on soldier safety, Steve Schofield is used to assessing the risk of tick-borne diseases such as Lyme disease and Powassan virus.
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But he found it deeply disturbing to read about a case like MaryAnn Harris’.
“I’m a scientist, so you try to be dispassionate about things. But when you hear a story like that…” he said.
“As a risk assessor, you look at the numbers. But you also need that personal perspective. These things do really, really bad things sometimes.”
Schofield regularly encounters ticks, both in his research and on the property near Dunrobin where he lives with his family and their dogs.
“Am I personally concerned about the Powassan virus? No,” he said. “Am I aware it’s there? Yes. Am I taking precautions? Absolutely.”
Deer tick populations are increasing, likely for a number of reasons. Climate change ensures that more ticks survive every year and the breeding numbers increase. More and more people go into the forest where they are likely to encounter ticks. Land-use changes could lead to an increase in deer populations, the most common hosts for ticks. Researchers have found a single deer infested with hundreds of ticks.
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“The deer do not transmit the virus. But what a deer is good for is making a lot of ticks,” Schofield said. “A mother tick wants to ingest a lot of blood and if she can do that, she will produce more eggs.”
Powassan virus is also transmitted by other ticks, namely marmot ticks and squirrel ticks, but Schofield describes these as “lazy ticks” that are unlikely to leave their hosts’ burrows and will cling to humans. In contrast, deer ticks are adventurers, climbing up vegetation and waiting to be picked up by whatever comes by, be it animal or human.
If caught early, Lyme disease can be treated with antibiotics. But there is no treatment for Powassan virus. As with Lyme disease, the best defense is to protect yourself from being bitten in the first place.
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“Usually you have to get to the ticks. The risk is a lot higher when you’re doing certain things,” Schofield said.
“If I’m walking a trail in the woods, I don’t usually wear protective gear, but I’ll definitely be checking for ticks. But when I’m working in the forest, cutting down trees, or working in the brush and scrub where the ticks are, I wear treated clothing.”
A deer tick lives for three years. In the first year, or larval stage, the ticks are not contagious and are likely to feed on small rodents such as the white-footed mouse. After overwintering, they enter the nymphal stage in their second summer. That’s when they pose the greatest threat to humans. The nymphs are still tiny and difficult to spot, but they’re more likely to be carriers of Lyme disease or Powassan virus and are more likely to find a human host and break away from it feed. After the second wintering, the ticks feed and reproduce in the third summer.
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While Powassan virus can cause serious illness, it remains rare compared to the more widespread risk of Lyme disease. And although ticks are now common in the Ottawa area, Schofield said the risk is manageable.
“What you don’t want is to stop people from getting outside and into nature.”
Prevention is the best protection:
• Assume that every natural area has ticks.
• Wear long-sleeved shirts and long pants tucked into your socks to minimize exposed skin. Light-colored clothing makes it easier to spot ticks. At the end of the day, throw your clothes in a hot dryer for 10 minutes to kill any invisible ticks.
• If possible, stay on paths and avoid tall grass or bumping into trees or bushes
• Use an insect repellent that contains DEET or Icaridin. Tick repellent clothing that has been treated Permethrin is also safe and effective.
• Examine yourself and your children all over their bodies, paying particular attention to toes, knees, armpits, groin and scalp, areas where ticks tend to attach themselves. Ticks can be tiny, no more than the size of a poppy seed for nymphs and the size of a sesame seed for adults.
• Remove ticks with tweezers or a tick tool, being careful not to squeeze an engorged tick or leave its head behind. The earlier a tick is removed, the lower the risk of infection.
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