Getting into the ‘tick’ of things

by Sarah Said | August 28, 2019 5:27 pm

A lone star tick questing on a leaf in response to movement.

It’s a picture-perfect day at the Konza Prairie, its lush tallgrass carpeting a hilly landscape that meets the bluest of skies in the distance.

It’s early, just shy of 8 a.m., the view a mosaic of various shades of green bathed in bright light. In the distance, a deer bounds effortlessly through the grass, its head and body rising and falling at a steady pace until it disappears into a dense group of trees on the other side of the field.

It’s the sort of setting you’d expect to see in a wildlife documentary—unspoiled and peaceful, the nearby trails beckoning to be explored.

“What does it mean when you see a white-tailed deer?,” asks Michael W. Dryden, DVM, MS, PhD, Dipl. ACVM, a university distinguished professor at Kansas State University (KSU). “Ticks!,” we answer in unison.

The lowdown on ticks

Donning protective coveralls and rubber boots duct-taped above the ankle, eight trade editors and writers wade into the mid-thigh-high grass, wary of the tips that are likely to yield the tick species inhabiting this part of northeastern Kansas, near the college town of Manhattan.

Within a matter of a few feet, several ticks had grabbed onto the drag, an indication of how easily the parasite can transfer itself and the likelihood of it finding a host to feed on.

It’s day two of Boehringer Ingelheim’s tick camp, a media-only event held in June in conjunction with the university’s College of Veterinary Medicine. Its purpose is to help improve our knowledge of tick biology, learn what’s new on the research front, and to get up close and personal with these blood-feeding parasites… very up close and personal. In fact, we’ve been warned the ticks will comply wholeheartedly through a behaviour called questing in which they perch on a blade of grass and extend their front legs in response to a host passing by. Ticks neither jump nor fly—all they need is physical contact to get themselves onto an animal or person. Their only goal is to feed, which they do until they’re engorged. The tick’s ability to produce anti-inflammatory proteins allows it to hide from the host’s immune system response. Whether animal or human, the host is unaware a tick is feeding on its blood until its firmly attached body is seen piercing the skin. The longer it’s attached, the more likely the host will become infected with a pathogen. Removing the tick as soon as possible is critical.

“Who has the drag?,” asks Kathryn Reif, MSPH, PhD, an assistant professor at KSU’s College of Veterinary Medicine. She’s referring to a 1-m2 (10-sf) piece of white cloth looped onto a wooden rod and weighted down with chain to better control it in windy conditions. Dragging is the method used to harvest ticks in the wild for study. Parasitologists drag the cloth along the top of grass, creating movement to entice ticks to attach.

Veterinary Practice News Canada editor Jacquie De Almeida suits up for a close encounter with ticks.

At Konza, it takes only a few steps before the cloth is peppered with ticks, both adult and nymph, most of the lone star variety (Amblyomma americanum). This particular tick is a vector of several diseases, including human monocytotropic ehrlichiosis (Ehrlichia chaffeensis), canine and human granulocytic ehrlichiosis (Ehrlichia ewingii), and Southern tick-associated rash illness (STARI).

“We’ve only gone a few feet. If a dog had walked along here, it would have been exposed to 20 ticks, minimum,” Dr. Reif notes. “People have no clue how heavy their or their pet’s exposure to ticks actually is.”

And that’s what makes them so dangerous, and year-round preventatives for pets so critical.

Minimizing exposure

According to the experts, blacklegged ticks are established in southern Manitoba, Ontario, Quebec, Nova Scotia, and New Brunswick. And while the American dog tick can be found across southeastern Canada, lone star ticks are not yet known to be established here.

Ticks are an ambush predator, requiring a blood meal to advance to the next life stage. Once a tick has found a host, it can remain attached anywhere from three to 14 days. Having its fill, the engorged tick detaches, and if it’s an adult female, it will lay several thousand eggs and then die. Understanding the tick life cycle and which life stages are more associated with transmitting pathogens helps inform the risk of pets and people being exposed to tick-borne diseases.

Members of the trade press participate in a tick drag.

“We have to really set our clients’ expectations, and that’s why knowing what ticks are in the area is really important,” says Brian Herrin, DVM, PhD, DACVM (parasitology), assistant professor at KSU’s College of Veterinary Medicine. “If you put a dog through a tick-infested area, it’s going to come out with ticks on it and there will be at least one tick that will feed to repletion if you don’t do something about it. That’s why we have to talk to our clients about tick risks and prevention, tick checks, and what to do to pull them off.”

On average, ticks live two to three years and feed at each life stage (larva, nymph, and adult). They can go a year without needing to feed, hibernating in warmer pockets of leaf litter to survive the winter months with the help of an ‘antifreeze’ protein in their blood. According to Reif, the pathogen a tick carries is intrinsically dependent on it to survive the cold winter months in order for it to be transmitted.

“Some of these pathogens have evolved the ability to help ticks through these hard times,” she says. “The pathogen upregulates the expression of the antifreeze proteins to the effect that infected ticks have a greater opportunity to survive those cold winter months than unaffected ones.”

Most of a tick’s life is spent off-host, which is one of the reasons why ticks are so difficult to control in the environment, Dr. Herrin says. “The challenge we have is that there are multiple tick species, and it doesn’t make a huge difference if they are all killed at the same rate,” Dr. Herrin explains. “There are some that are just heartier than others. The lone star tick is much more difficult to kill than the blacklegged tick… It’s really challenging to kill enough ticks to hurt the population.”

“Ticks spend about 99 per cent of their life in the environment, so we are really only able to do something about the ticks your dog encounters. We have no way to manage that environment, so we have to have tick prevention.”

Source URL: