A blacklegged tick, also known as a deer tick. Besides Lyme disease, the most common tick-borne illness in Canada, ticks can transmit anaplasmosis, which can be fatal in rare cases.James Gathany/The Associated Press
It was fear, at first, that drove Kirsten Crandall to learn about ticks.
Ms. Crandall knew of two family friends who developed Lyme disease after being stealthily bitten. And since they hadn’t realized they’d been exposed to ticks, they weren’t diagnosed right away with the illness, which if left untreated, can lead to heart palpitations, nerve pain and brain swelling.
Rattled by their experience, Ms. Crandall decided to arm herself with knowledge. Once she began studying ticks, however, her fear turned into fascination.
“I really just went down this very detailed sort of rabbit hole,” said Ms. Crandall, who is now a PhD candidate in the departments of biology at both McGill University and the University of Ottawa.
What to know about ticks and Lyme disease in Canada
Ticks are a growing, disease-carrying menace. Besides Lyme disease – the most common tick-borne illness in Canada – they can transmit other diseases such as anaplasmosis, which can be fatal in rare cases, and babesiosis, an infection that destroys red blood cells.
And bites from lone star ticks, which are endemic to the U.S. and occasionally found in Canada but with no evidence yet of established populations in this country, may trigger an allergic reaction that causes some people to feel sick to their stomachs after eating meat. So it’s no wonder these bloodthirsty parasites often inspire horror and revulsion.
But as scientists who study them explain, ticks are also captivating and little understood creatures. And getting to know them better – by understanding their physiology, behaviour and where and how they’re spreading – is the key to protecting ourselves and our pets against them and the various pathogens they carry.
To Ms. Crandall, what makes ticks so interesting is that they’re ingeniously sneaky, yet, as she put it, “really prehistoric at the same time.”
Ticks don’t have eyes, but instead, find hosts by using a sensory organ near the end of their forelegs that detects carbon dioxide, she explained. They’re not particularly efficient at seeking hosts, but when they do find one, they’re great at evading detection. Their saliva contains compounds that ensure their hosts don’t feel pain or itching, and it prevents the host’s blood from coagulating, which allows the ticks to feast.
Through her research, Ms. Crandall has found ticks infected with Babesia odocoilei, the protozoan that causes babesiosis, and Rickettsia rickettsii, the bacterium that causes Rocky Mountain spotted fever, in areas of southeastern Quebec, beyond where they’ve previously been found.
Rickettsia rickettsii was found in rabbit ticks, which rarely bite humans. But the presence of the pathogen could potentially lead to more infection among local wildlife populations, she said. (In humans, Rocky Mountain spotted fever causes headaches, fever and rashes, and can be deadly if it isn’t treated early.)
As climate change and land fragmentation alter the movement patterns of birds and mammals that are hosts for ticks, the geographical range of those that carry diseases is expanding.
Not all ticks carry diseases, and not all ticks feed on humans, however. According to Kateryn Rochon, an associate professor of entomology at the University of Manitoba, there are about 40 species of ticks in Canada, and most of them have a preferred host. Rabbit ticks, for example, are usually found on rabbits, and groundhog ticks on groundhogs.
Ticks that are “generalists” feed on a variety of animals, and humans can wind up as incidental hosts.
Ticks start life without infection, according to Stephen Rich, professor of microbiology at the University of Massachusetts Amherst. Those that can transmit Borrelia burgdorferi, the bacterium that causes Lyme disease, can acquire it when they feed on infected white-footed mice.
“And then if we’re unfortunate enough to be the next host, we get that infection,” said Dr. Rich, who is also executive director of the New England Center of Excellence in Vector-borne Diseases.
In the adult stage of their life cycle, black-legged ticks go on to feed and breed on the backs of deer. But here, a curious thing happens. For decades, scientists have known that something about white-tailed deer seems to kill the Lyme bacterium, Dr. Rich said. New research by Patrick Pearson, a graduate student at his lab who recently finished his PhD, finally provides some answers.
Dr. Pearson grew Borrelia burgdorferi in culture and spiked it with the serum, or the fluid component of blood, of white-tailed deer. The serum alone was sufficient to kill the bacteria, Dr. Rich said.
Theoretically, this finding could lead to “another tool in the toolbox for treating Lyme disease,” Dr. Rich said, because if researchers can determine precisely what the killing component is, they can think about ways to pharmacologically imitate it.
Currently, a vaccine for Lyme disease by Pfizer and vaccine company Valneva is in late-stage clinical trials. But getting such a vaccine to market is not the end of the fight against tick-borne diseases.
Lyme disease is the most common
tick-borne illness in Canada
There are two types of ticks that carry Borrelia burgdorferi, the
bacteria that cause Lyme disease in humans: The black-legged or
deer tick is found in southern and eastern Canada, and the western
black-legged tick in the West. They go through a two-year life cycle.
The ticks can become vectors of the Lyme disease-causing bacteria
after feeding on infected birds or rodents. Humans often contract the
disease after being bitten by tiny ticks in the nymph stage.
To prevent disease, ticks should be removed within 48 hours.
Black-legged or
deer tick
(Ixodes scapularis)
Western
black-legged tick
(Ixodes pacificus)
Relative sizes
Adult
female
Adult
male
Nymph
Larva
1 cm
Early signs and symptoms of Lyme disease
They usually start three to 30 days after you have been bitten by an infected black-legged tick. Most people experience mild flu-like symptoms soon after being bitten, while a small number may have more serious symptoms, sometimes weeks after the bite.
Headache
!
Fatigue
Chills
Swollen
lymph nodes
Rash Sometimes shaped like a bull's eye
Fever
Muscle and
joint aches
john sopinski and MURAT YÜKSELIR / THE GLOBE AND MAIL
SOURCE: GOVERNMENT OF CANADA; univ. of rhode island
Lyme disease is the most common
tick-borne illness in Canada
There are two types of ticks that carry Borrelia burgdorferi, the
bacteria that cause Lyme disease in humans: The black-legged or
deer tick is found in southern and eastern Canada, and the western
black-legged tick in the West. They go through a two-year life cycle.
The ticks can become vectors of the Lyme disease-causing bacteria
after feeding on infected birds or rodents. Humans often contract the
disease after being bitten by tiny ticks in the nymph stage.
To prevent disease, ticks should be removed within 48 hours.
Black-legged or
deer tick
(Ixodes scapularis)
Western
black-legged tick
(Ixodes pacificus)
Relative sizes
Adult
female
Adult
male
Nymph
Larva
1 cm
Early signs and symptoms of Lyme disease
They usually start three to 30 days after you have been bitten by an infected black-legged tick. Most people experience mild flu-like symptoms soon after being bitten, while a small number may have more serious symptoms, sometimes weeks after the bite.
Headache
!
Fatigue
Chills
Swollen
lymph nodes
Rash Sometimes shaped like a bull's eye
Fever
Muscle and
joint aches
john sopinski and MURAT YÜKSELIR / THE GLOBE AND MAIL
SOURCE: GOVERNMENT OF CANADA; univ. of rhode island
Lyme disease is the most common tick-borne illness in Canada
There are two types of ticks that carry Borrelia burgdorferi, the bacteria that cause Lyme disease
in humans: The black-legged or deer tick is found in southern and eastern Canada, and the western
black-legged tick in the West. They go through a two-year life cycle. The ticks can become vectors of
the Lyme disease-causing bacteria after feeding on infected birds or rodents. Humans often contract the
disease after being bitten by tiny ticks in the nymph stage. To prevent disease, ticks should be removed
within 48 hours.
Black-legged or
deer tick
(Ixodes scapularis)
Western
black-legged tick
(Ixodes pacificus)
Relative sizes
Adult
female
Adult
male
Nymph
Larva
1 cm
Early signs and symptoms of Lyme disease
They usually start three to 30 days after you have been bitten by an infected black-legged tick. Most people experience mild flu-like symptoms soon after being bitten, while a small number may have more serious symptoms, sometimes weeks after the bite.
Headache
!
Fatigue
Chills
Swollen
lymph nodes
Rash Sometimes shaped like a bull's eye
Fever
Muscle and
joint aches
john sopinski and MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE: GOVERNMENT OF CANADA;
univ. of rhode island
For Monika Gulia-Nuss, a molecular biologist at the University of Nevada, Reno, that work has just begun. Dr. Gulia-Nuss and her team have come up with a way to use CRISPR-Cas9 technology to gene-edit ticks in the embryo phase, something scientists previously had attempted but failed to do.
In a critical step, they removed a gland in female ticks that coats each of her eggs with a waxy protective layer, which allowed the researchers to inject the eggs with materials necessary for gene modification.
This technique opens the door to studying ticks at a molecular level. Until now, Dr. Gulia-Nuss said, a lack of tools for researchers to do so has meant “there are a lot of black boxes that we don’t know yet about tick physiology.”
Her work could also lead to the development of further vaccines. Dr. Gulia-Nuss said a vaccine for a single tick-borne illness won’t cut it, and in fact, relying too heavily on one might backfire.
“People will think, ‘Oh, I’m vaccinated. I don’t have to worry about ticks,’” she said, and they may let their guard down against other tick-borne pathogens.
Dr. Rochon at the University of Manitoba also cautions against betting on any single measure. Controlling ticks requires a multipronged approach that focuses not just on human health, but on the health of the environment and other animals, she said.
In the meantime, she said, there is a lot people can do to avoid bites, including using insect repellent, wearing protective clothing, habitually checking for ticks on their body, and showering immediately after spending time in areas – particularly where there’s shade and grass or undergrowth – where ticks may be.
She also recommends using eTick.ca, a surveillance website based out of Bishop’s University that allows people to submit photos of ticks for identification.
“Summer is so short. You don’t want to be stuck inside because you’re afraid of ticks,” Dr. Rochon said. “But knowing that you can do something, you are empowered.”