Ticks are good picnic guests to avoid
‘I t’s no picnic to be a tick,” she says, waving her four of her eight legs at me, “but my sidekick and I can join your picnic pretty quick.”
“No, thanks.” I edge away from her. “I prefer my picnics without Lyme disease or any other disease you might be carrying.”
“Hey, I’m just trying to raise a family.”
Ixodes pacificus is one of Vancouver Island’s resident tick species. Called the western black-legged tick and sometimes even the deer tick in regular English, it’s common on the south coast through spring and early summer. With our mild winters, however, we can encounter them at any time of year.
Ticks of all ages and sizes bite. (“That’s not a very nice thing to say,” she says.) Female adult ticks need blood to develop their 2,000 or so eggs. Once the eggs hatch, the six-legged larvae chomp on rodents and birds to get the nutrient boost they need to become nymphs. After the nymphs eventually transform into eight-legged adult ticks, these prey on whatever blood-filled critter they can bury their heads into — deer, rabbits, dogs, cats, birds, reptiles, amphibians, humans — they’re not picky.
They even feed on each other. A micro-photo published online recently shows a male tick with its head burrowed deeply into the abdomen of a massively blood-bloated female tick.
It just goes to show you what we’re dealing with here.
(“Hey!” she says. “That’s totally uncalled for! Or mostly uncalled for. Oh, never mind.”)
Because of these habits, all ticks are at risk of picking up and carrying diseases from one host to the next.
For example, Borrelia mayonii isn’t a condiment for your picnic sandwiches or salads. It’s one of many bacterial species that can infect ticks and, through ticks, infect other animals. The microbe causes an illness similar to Lyme disease, with fever, headaches, sore joints and lasting, difficult-to-treat symptoms.
In 2016, researchers found the bacteria in ticks in southwestern B.C., although no illness was reported.
Researchers also found a sub-strain of Borrelia burgdorferi, the bacterium that causes Lyme disease, in three different tick species feeding on rabbits on Vancouver Island. This brought the number of tick species on the Island that are known to carry Lyme disease to four.
Other tick-borne diseases include Rocky Mountain spotted fever, babesiosis, tick-borne relapsing fever, ehrlichiosis, tularemia, Heartland virus and Powassan virus — all nasty and often hard to diagnose or treat.
The incidence of Lyme disease is increasing across Canada. In 2009, 144 cases were reported. In 2015, more than 900 infections were diagnosed.
The increase is due in part to increased awareness and better reporting and diagnoses.
It’s also due to more infected ticks. Weather and climate shifts mean the bugs are active for longer throughout the year, increasing the chances of tick bites. The shifts also encourage tickcarrying animals, such as birds, to migrate further north from Lyme disease–infested regions in the U.S., spreading the infection. And the more infected hosts there are, the more infected ticks to spread Lyme disease and other illnesses to new hosts.
But before infecting humans, the pathogens must first get past a tick’s defences.
Ticks lack the genes for the usual immune response to bacteria. Scientists have found, for example, that the bacteria that cause Rocky Mountain spotted fever hijack the bug’s immune system. The microbe makes the host tick produce a protein that changes the bug’s gut, allowing the bacteria to colonize the gut at will. It’s possible Borellia bacteria use a similar trick.
And once the bacteria colonize the gut, they’re primed for the bug’s next blood meal. Blood nutrients trigger the pathogens to reproduce rapidly. By the time the tick finishes feeding — sometimes after two or three days — and vomits some of the blood, it’s just ingested back into the host (“I couldn’t take another sip”); the regurgitated blood is well spiked with the diseasecausing pathogens.
“You know, not all us of are infected,” the tick says. “You can’t generalize and call all of us diseased just because of a few unfortunates among us. That’s, like, discrimination.”
In the case of ticks’ potential to carry disease, why take the chance? A tick’s life might not be a picnic, but it’s wiser to not let them picnic on you.