/Uptick in tick populations brings crowd to parasitologist’s presentation

Uptick in tick populations brings crowd to parasitologist’s presentation

By Sue Tiffin

When Dr. Andrew Peregrine, professor and clinical parasitologist at the Ontario Veterinary College moved to Southern Ontario in 1997, he said the prevalence of ticks in Ontario was not what it is now.

“I distinctly remember shortly after I arrived, saying, what do you teach the vet students about ticks? And literally, [the person retiring] said to me, you don’t really need to bother, it’s not an issue,” Peregrine told a gathering of hundreds of people tuned in to a presentation called An upTICK on Ticks on Lyme Disease in Eastern Ontario. “And essentially that probably was true back in the 1990s, but things, as you more than anyone would be aware, have changed significantly since that time.”
The June 8 virtual meeting, hosted by The Friends of the Napanee River and Friends of the Salmon River and joined by Environment Haliburton in lieu of an enviro-cafe, saw more than 250 people log in to the live presentation and more than 400 view the video in the week since the meeting. Much of the reason for the interest is that in the past few years, climate change has led to a major increase in tick populations with Health Canada reporting more than 990 cases of Lyme disease in 2016 – most of these cases from Ontario, Quebec and Nova Scotia – compared to 144 cases in 2009. Since the Lyme disease case definition was updated, case counts have jumped to more than 2,600 in 2019.

While Peregrine treats animals and not humans, he spoke to what types of ticks commonly transmit pathogens and how to identify them, how Lyme disease is spreading and how Lyme disease presents in people.
Though in the past, Peregrine said, there was really only one tick that was found on animals and so looking closer at the insect wasn’t necessary, now it is important to identify a tick.
“Today, things have changed,” he said.

While in textbooks there are at least seven different ticks across North America that can be found on humans or pets, Peregrine said the original tick here was the American dog tick (Dermacentor variabilis), and the tick that has invaded southern Ontario is the deer (or black-legged) tick (Ixodes scapularis). The Lone Star tick (Amblyomma americanum) is occasionally here, he said, falling off of migrating birds, but there is not yet evidence that it is established here.
To identify a tick, Peregrine said it’s important to learn the difference between the scutum of the most common ticks – the American dog tick scutum is multi-coloured, and the deer tick’s scutum is dark brown. The deer tick is the tick that is associated with the transmission of the bacteria called Borrelia burgdorferi, the bacteria that causes Lyme disease – named for the area of Connecticut it was first diagnosed in, explained Peregrine, while the American dog tick – “at the moment that’s a ‘good tick’ in Ontario” – does not carry bugs or pathogens harmful to humans that we have identified.

Ticks investigated for Borrelia burgdorferi are also immediately screened for Anaplasma phagocytophilium, with an occurrence rate of three per cent, and Babesia microti, which shows up about one per cent of the time.
“Of all the tick-borne diseases in North America, Lyme disease is by far the most important,” said Peregrine. “All those three things will infect people, by far the most common in Ontario is Lyme disease.”
The deer tick, which like feeding on white-tailed deer, ingest blood so that they can produce eggs once they’ve dropped off an animal.
“Once a tick is fully fed, on white-tailed deer, the female tick drops off into the environment and she lays her eggs in the environment,” said Peregrine. “The most ideal environment for that tick and the eggs to develop is essentially brush and grass on the edge of deciduous forest. It’s much less common in coniferous forest areas.”
If the female tick is infected with Borrelia burgdorferi, or the bug that causes Lyme disease, she does not transfer that to her offspring.
“So the obvious question is then, well, how do they get infected?” asked Peregrine.

The eggs hatch to release a tiny structure – larva – that has three pairs of legs rather than the four pairs of an adult. To mature they need blood which they typically find on wild rodents including white-footed mice, shrews, voles, and also birds.
“They feed on the rodents because they need blood to mature, however if that blood contains the bacteria Borrelia burgdorferi, they will get infected with that bacteria, and once they get infected they remain infected for life,” said Peregrine. “So it’s wild rodents, and particularly white-footed mice in southern Ontario that are extremely important to the risk of these ticks getting infected. They get infected with the bug that causes Lyme disease. It doesn’t usually make them sick but it circulates in their blood for at least a number of weeks or months, so that when the larvae feed on the mice, not only do they take in blood but they get infected with the bacteria that causes Lyme disease.”

The larva then drops to the environment where it moults to a nymph, which also tends to feed on rodents – but also birds and people. It can also acquire the bug and be infected for life.
Typically it is the immature adult that we end up seeing on ourselves, or pets, said Peregrine. Ticks will wait to come into contact with animals.
“What influences the risk of exposure to ticks? Number one, you’ve got to go outside, you’ve got to walk into their environment, and unlike fleas that hunt for people or pets, ticks literally crawl up blades of grass, and they then extend their [front legs]. It’s called questing – they’re literally just waiting for you, me, or our pets to walk by and then they will transfer onto ourselves.”

There are two peaks, or times of the year, for them to be found. They first appear in September or early October, and then those that survive winter under the snow reappear in spring, in April, May or June.
Until about 1995, the only place in all of Canada where the deer tick was known to establish, said Peregrine, was Long Point in Lake Erie. As the tick then began appearing in multiple places across Canada, the Public Health Agency of Canada began asking people to send ticks when they found them – so they could be documented by location, and also so that they could be screened.

Maps Peregrine showed during the presentation show a significant spread of ticks throughout southern Ontario, in Eastern Ontario, southern Quebec, the Maritimes and the southern part of Manitoba. In 2021, a pocket of endemic population has been found just north of Peterborough. Just in the past six months, he said, they’re being seeing in Guelph.
“When you first see them in an area, it’s important to ask the question, is this what’s called an adentitious tick and that’s essentially a tick that’s fallen off a migrating bird, or does that tick represent part of an actively breeding population?,” he said. “It’s important to differentiate the two, because it’s the latter, an actively breeding population, the risk of contact with the tick and the risk of Lyme disease is quite different.”

Local public health units will drag an area, then return a second year to determine if the population is endemic.
Thousands of ticks, said Peregrine, come to Ontario on migrating birds, especially from the northeastern part of the United States, every spring. While there has always been bird migration, the number of ticks in the U.S. has increased significantly. Changes in deer population and reforestation has caused tick populations to increase. And it’s very clear, said Peregrine, “that climate change has certainly been driving, at least in part, the changes in distribution.” Eastern Ontario is providing the ideal and correct temperature and humidity for best propagation and establishment of the tick. In 2007, 7.5 per cent of ticks submitted from Ontario to the Public Health Agency of Canada were found to have Borrelia burgdorferi, and in 2013 that number increased to 18.4 per cent.  
“So the longer the tick is in the area, the more common infection typically is in these ticks,” said Peregrine.

To acquire Lyme disease through ticks, a tick must feed on a person for at least 36 hours to transmit the bug that causes Lyme disease. Usually within the first month of infection, a large, red, circular, sometimes bulls-eye rash at least five centimetres in diameter can appear – typically in 60 to 80 per cent of people, and usually seven to 14 days after the tick’s contact.
“So it’s a lot larger than a common bug bite and it develops much more slowly than, for instance, a mosquito bite, associated with the bacteria multiplying and spreading in the skin.”

Also in the first month, some people can complain of muscle or joint pain and flu signs. Most cases are treated with a few weeks of antibiotics.
“If the infection is caught in that early stage, typically infection in people and in dogs responds very quickly to treatment. However, if the bacteria then spreads around the body after that, it can be much more difficult to treat.”
Will you or your pet get Lyme disease? It has to be the right tick – the one associated with Lyme disease – that has been well-fed for at least 36 hours and has to be carrying the bug. The overall proportion of all the ticks in Eastern Ontario infected in 2016 was 23 per cent, said Peregrine.

If you have a dog, he suggested speaking to a vet about oral or topical tick products, or to consider a vaccine, which is available for dogs. [While human vaccination is not yet possible, Peregrine said there is a good chance it will one day exist, which “would change the world once they come on the market.”]
“Every day after walking in tick areas: check daily for ticks,” he said. “Because if you check the dog every 24 hours for ticks, and pull them off before they’ve fed long enough to transmit the bug that causes Lyme disease, you can essentially eliminate the risk.”
It’s a good idea to get in the practice of tick checks on ourselves – like those in Lyme, Connecticut now – on a daily basis, he said.

Be cautious walking in the woods, avoiding bushy and grassy areas if possible, tuck long pants into socks and wear long-sleeved shirts, and potentially use tick repellant but be mindful of pyrethrin which can be extremely toxic to cats. Ticks can be the size of a poppy seed, so though they can be removed with tweezers at home, a visit to a physician for removal is recommended.

To view Peregrine’s presentation on YouTube, visit https://www.youtube.com/watch?v=6WTo5cmqExQ. For more information on Environment Haliburton visit https://www.environmenthaliburton.org/