Waiting Like a Tick
Tick on a Leaf
Tick species - Dermacentor andersoni

Written by Fred Bunnell

I still call it the Deas Island tunnel. It’s a  synonym for waiting, at least in human terms (see blog Time and Space is in the Eye of the Beholder). We’re moving though, jerky, shift up, shift down (I still drive a standard). Can’t let the mind wander too much. That guy, he’s cut in, gained a car length, a few seconds. Couldn’t wait. Not like a tick.

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Rocky Mountain Spotted Fever
Rocky mountain Spotted Fever from Centers for Disease Control and Prevention

Ticks could teach us a lot about patience, but mostly they irritate or even frighten us. Like leeches. A lot of wee creatures irritate us – black flies, mosquitoes, fleas – but only rarely do they frighten us. Ticks are particularly spooky because they transmit the widest variety of pathogens of any blood sucking arthropod, including bacteria, rickettsiae, protozoa and viruses.

There also seems to be something especially repugnant when we emerge from some cooling lake or scratch our head to find some creature firmly ensconced and feeding on our blood. It may be this audacious, self-confident violation of our bodies that makes ticks so damnably offensive. That and largely unfounded fears of them burrowing into our innards, or the well-founded fears of them infecting us with a debilitating disease. Someday I may write about ticks, wildlife, man and diseases but my mind is in the tunnel and wondering about patience.

Dermacentor andersoni Tick Species
Tick species - Ixodes pacificus
Above: Dermacentor andersoni
Below: Ixodes pacificus
Ken Gray photos

At least 23 species of ticks live in BC. This tale focuses on three. The Rocky Mountain wood tick (Dermacentor andersoni) transmits Rocky Mt spotted fever. It and the two ticks found to transmit Lyme disease (Ixodes pacificus and Ixodes angustus) are all ‘hard ticks’ (Family Ixodidae) –difficult to scrunch when they’re on you. Details of biology differ among ticks. The points here refer to hard ticks (soft ticks are a whole different group).

I knew nothing about the patience of ticks when I first encountered them in disconcerting numbers. I did know enough about Rocky Mountain spotted fever or tick paralysis to be wary and quickly learned they were magic. Two of us were working in the forests of Saskatchewan measuring trees. Each evening upon return to the tent, we would strip, remove ticks and toss them in the bonfire. A competition arose – who had the most? The numbers became worrisome after they exceeded 50; we began to take precautions. Despite it being summer, shirt collars were buttoned, elastics put on cuffs, pants tucked into socks, no coffee for breakfast (our flies would stay closed as long as possible). The first evening after all these precautions, John won. He extracted 103 ticks. True magic; miniature Houdinis in reverse.  

My mind wanders a bit when I move only a few feet at a time. The tunnel traffic reminds me of how ticks achieve their magical entrance. It becomes even more fascinating when we remember that they are blind, breathe through their sides, smell with their front legs and swallow through their brains. Their expertise is directed by other senses but enabled by marvelous patience.

Hard Tick Mouth Parts
Hard tick mouth parts. Department of Entomology, UC Davis.
The rod-shaped structure in the center plunges into the host’s skin while feeding. The backward directed projections prevent easy removal of the attached tick. In addition, most hard ticks secrete a cement-like substance produced by the salivary glands which literally glues the feeding tick in place; the substance dissolves after feeding is complete.

Hard ticks pass through 3 stages – larva, nymph and adult. Members of the family can be grouped into one-, two- or three-host ticks, depending on how many stages require a new blood meal. The typical new tick is incomplete when it emerges from its egg; it lacks a pair of legs and sex organs. However, it is ready to feed and needs a blood meal before developing into an 8-legged nymph. It ambushes its blood source from some perch on the tip of a blade of grass or other leaf. Then it grows, shedding its skin like outgrown clothes, and develops the missing organs to become an adult. Individuals usually take a single blood meal (usually from a mammal) before proceeding to the next stage. It can take several years to get through all stages.

The fed adult stage is terminal. After laying one batch of eggs, the female dies. After the male has reproduced, he dies as well.

That seems an uneventful life. Perhaps it is. It is certainly dominated by patience. The hunt for blood of a warm-blooded animal is critical. Without blood no eggs will develop. The hunt is not a stealthy walk or rapid pursuit. That would be wasteful. Ticks feed on animals much larger and more mobile than they are. It is more efficient to let those animals come to them than to chase them. The hunting behavior of hard ticks is often called “questing.”

They’re clever little beggars. They don’t climb above your swing set and jump on your kid’s heads as they swing. They don’t jump from trees or vegetation if you walk near them. They waste no energy, but lay in wait for the perfect host to brush by them. They climb to the very tip of a leaf or blade of grass and stretch out their first pair of legs waiting to grab onto any host that brushes by. Once aboard, they quickly climb upwards to find a dark, near-hidden place to latch on for a blood meal.

Tick on Leaf
Ixodes pacificus  Dave Macchia

Normally, a tick will climb vegetation that is the perfect height to grab hold of the host they are after. For instance, when a tick is in the larva stage it prefers small rodents and will quest in the low vegetation and underbrush where those critters have left evidence of past travels. Nymph (teenage) and adult ticks find taller vegetation, up to knee height so that they can grab onto bigger mammal hosts (including us) who brush by. Ticks do not normally climb higher than knee height, nor do they jump down on your head from a tree branch. The reason you find a tick on your head or neck is either: 1) you were bent down, sitting or lying in a place where they were able to climb on, or 2) (most likely) they latched on at knee level or lower and quickly climbed upward.

Generally, both female and male ticks quest for a host, but for different reasons; the female for a blood meal, the males to search the host for female ticks in order to mate and sometimes feed from them. Males may parasitize female ticks by piercing their cuticle with their mouthparts to feed on their haemolymph (tick blood); up to 3 or 4 males have been found feeding on one female tick. Until recently we had assumed that they were exclusively after mammals for their  last blood meal. Recent work, inspired by lyme disease, has found that birds also serve as incubators and distributors of ticks and lyme disease.

The questing tick is seeking a vantage point from which it can drop or grab onto mammals as they pass by. It is an ambush hunter seeking a watch tower despite being blind. The upward movement is directed by photosensitivity of the skin. Blind and deaf, the adult female waits for her last meal. It won’t do to grab onto any creature that passes by. Nor should it respond to just any movement – raindrops, wind or a falling branch. Somehow the blind and deaf highwaywoman must find a warm-blooded creature, most often a mammal.

Ticks exploit a variety of stimuli in this search: touch, movement, heat, humidity, exhaled carbon dioxide and butyric acid in mammalian sweat. Blind and deaf, the tick senses its environment with the Haller’s organ on its front legs. Magic again. Once the potential meal is sensed it drops or grabs onto the host. If it misses and falls on something cold it will climb up and wait again. Once on target, all that remains is to find a hairless part, grab on with those sticky feet, insert the well-designed mouthparts and pump itself full of blood. They lack a sense of taste. If given membranes with fluids other than blood, they will drink most fluids of the right temperature.

Hard ticks feed for extended periods of time on their hosts, varying from several days to weeks, depending on such factors as life stage, host type and species of tick. The outside surface, or cuticle, of hard ticks actually grows to accommodate the large volume of blood ingested. In adult ticks that can be anywhere from 200 to 600 times their unfed body weight.

Ixodes Tick
Well-fed and hungry Ixodes ticks. The unfed one may be a male looking for a meal. Anders Madsen photo.
Waiting Like a Tick
From web article on meat allergies.

The pursuit of that last meal is an act of suicide. Once replete with blood, the female tick drops to the earth, lays 4,000 to 10,000 eggs and dies. If she has failed to find blood her eggs will not survive. It is in great part luck that brings a mammal close to her perch. The longer she can wait, the more likely a mammal will pass by. Her patience is remarkable. At the Zoological Zoo in Rostock, starving ticks have remained alive for 7 to 18 years.

Now there’s a rear-ender. Cut in; couldn’t wait. Not like a tick.

p.s. If you find a tick on you or your dog do not rush to pull it off. That simply decapitates the tick leaving the mouthparts anchored in the skin which can cause a local infection, quite apart from the risk of disease. Better to smear the tick with petroleum jelly, especially the back of its body because this is where it breathes. Being suffocated causes the tick to release its grip. You can then remove it easily by twisting it close to its head (tweezers help). Wash and disinfect the point of attachment and keep a watch on the bite. If  a rash starts to develop (as distinct from the normal inflammation following a bite), see a doctor or vet quickly. I have spent enough time in the woods, often walking a dog, to have gently unscrewed 100s of ticks from myself, other humans or dogs without jelly or tweezers, but suffocating the tick helps.

p.p.s. Climate change has welcomed a new tick to Canada from the south. It is still relatively rare but will spread. It’s bite can cause an extreme allergy to red meat.  The species is distinctive.

Fred Bunnell
Fred Bunnell