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N.B. professor aims to broaden tick research after battling Lyme disease
When Vett Lloyd was bitten by a tick in 2011, it marked the beginning of a painful, years-long battle with Lyme disease. It also abruptly altered the trajectory of her career.
At the time, Dr. Lloyd's research at New Brunswick's Mount Allison University was focused on cancer biology but she wondered why people weren't paying more attention to ticks. So, she converted her cancer lab into a tick lab and reoriented her life's work around the tiny bloodsucker that nearly ruined her.
It was a scientific pursuit with a surprisingly therapeutic perk.
'When testing ticks, the first step you do is grind them into oblivion,' she says. 'And I must admit, it took me about 10 years to get over the joy of doing that.'
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Dr. Lloyd would still love to see ticks 'disappeared from the face of the Earth.' But 13 years studying the parasitic arachnids have forced a begrudging admiration as well, both for their fascinating biology and remarkable ability to spread.
Ticks, which are cousins of spiders and scorpions, have been crawling the planet for about 99 million years, according to fossil evidence showing that they once fed on dinosaurs. But in countries such as Canada and the United States, their numbers have risen dramatically in recent decades and ticks are increasingly recognized as a growing threat to public health.
In Canada, some 40-odd tick species have been documented, Dr. Lloyd says – but only a handful are adept at biting people or spreading human disease. One species that's expert at both is the Ixodes scapularis, also known as the blacklegged tick or deer tick.
It was once ignored by the public-health establishment. That all changed after 1976, when authorities in Lyme, Conn., reported a cluster of children with unexplained arthritis – an illness later attributed to the bacterium Borrelia burgdorferi, which is primarily spread through tick bites.
Today, blacklegged ticks are a known vector for seven human pathogens: five bacteria (including the Lyme bacterium), one parasite (that causes a malaria-like illness) and a rare virus called Powassan, named for the Ontario town where it was discovered after the death of a five-year-old.
Just three decades ago, there was only one spot in Canada where blacklegged ticks were known to be endemic: Long Point, Ont., along the shores of Lake Erie. But just across the U.S.-Canadian border, ticks were on the rise – as were the diseases they spread.
Every year, millions of ticks are biting birds that fly into Canada. A 2008 study estimated that northward-migrating birds carry anywhere from 50 million to 175 million blacklegged ticks into Canada every year – all of which drop off their feathered hosts once they finish feeding.
'Canada's being bombed by ticks in the spring,' says Nick Ogden, first author of the 2008 migratory bird study and director of the modelling hub division with the Public Health Agency of Canada.
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'And when the temperatures rise to a suitable level for the ticks, they can start off a population.'
In 2019, researchers conducted Canada's first real-time surveillance study of tick populations and found Ixodes ticks in every province except Alberta, Saskatchewan and Newfoundland and Labrador. Of the 567 ticks collected, 25 per cent were infected with the Lyme bacterium.
(In British Columbia, Lyme disease is less of a concern because another tick species – the Ixodes pacificus, a far less competent vector – is prevalent.)
Climate change has been a major driver of their spread. Ticks were already capable of surviving Canadian winters under certain conditions, Dr. Ogden says – for example, if they find a cozy leaf layer, where the microclimate might keep temperatures closer to zero. 'And they've got a bit of antifreeze in their bodies, which protects them,' he adds.
But the warming planet is resulting in more cumulative days with temperatures above zero – a key threshold for ticks to survive and thrive, according to Dr. Ogden's research. Given that female ticks can lay between 2,000 to 3,000 eggs in a single clutch, it doesn't take long for their numbers to explode.
'Nationally, it's really exponential what we're seeing,' says Manisha Kulkarni, the scientific director of the Canadian Lyme Disease Research Network and a professor at the School of Epidemiology and Public Health at the University of Ottawa.
'The abundance of ticks is really increasing ... which is leading to that amplification of tick-borne pathogens and that potential for spillover.'
The key to fighting ticks? Getting to know them better
Every person who contracts Lyme will have unwittingly supplied one of the three blood meals that a blacklegged tick requires over its lifetime, which can span two to four years.
Newly hatched from its egg, the six-legged tick larvae will die without its first blood meal. 'So, the mom usually lays her eggs close to a mouse burrow,' says clinical microbiologist Muhammad Morshed, program head for zoonotic disease and emerging pathogens at the BC Centre for Disease Control. 'They can easily hop onto mice or some other warm-blooded animal.'
Rodents are natural reservoirs for the Lyme bacterium, however. So, this first feed often infects the tick, which continues harbouring the pathogen even after moulting into an eight-legged nymph.
Blacklegged ticks don't seek out people. But their primary strategy for finding a blood meal is to climb a leaf or blade of grass, outstretch its front legs, and simply wait. If the first warm-blooded creature to come along is human, so be it.
For the first 24 hours after biting, the tick is mostly just salivating and preparing for what scientists refer to, somewhat horrifyingly, as the 'big sip.'
'It's not really getting a lot of blood at first,' says Rebecca Eisen, a research biologist with the U.S. Centers for Disease Control and Prevention's division of vector-borne diseases.
'But it keeps on feeding, and then it just gets the big sip and engorges.'
Ticks need strategies for staying attached. It helps to be a nymph, which is the size of a poppy seed and therefore tough to detect. Their mouthparts also have barbs and their salivary glands secrete an adhesive substance known as 'tick cement.'
And generally, an infected tick needs to be embedded for more than 24 hours before disease transmission occurs, Dr. Eisen says. 'The blood getting into the midgut tells [the bacteria] 'Hey, we found a host,'' she explains. 'Then they'll start the migration into the salivary glands.'
In its final life stage, the adult tick is trying to mate. A female needs a third and last blood meal to lay her eggs, so tick copulation mostly occurs on larger mammals – primarily white-tailed deer, an animal that's enjoyed a population resurgence in recent decades.
As ever more millions of ticks embark upon this life cycle in Canada, Dr. Lloyd hopes her research will help people live more safely among their exploding numbers. Her lab is looking for better diagnostics, as well as answers to basic science questions – why, for example, do ticks seemingly have a greater hunger drive when they're infected?
Pulverizing ticks may have provided early satisfaction for Dr. Lloyd, but her research has always been driven by a deep and personal understanding of the misery these bloodsuckers can cause.
She still thinks of the man who once left her a voice mail, desperately seeking help for his chronic Lyme symptoms. When she phoned back, she learned that he had died by suicide.
'It's not just a nine-to-five job for me; I want to try and help,' Dr. Lloyd says. 'I've seen the devastation this causes.'
