by Janice Willard DVM, from the August 2006 Newsletter

While I enjoyed most of my classes in vet school, I’ll have to admit that one of them, Parasitology, gave me the willies. The problem was that I really don’t like creepy crawlies. And I am not alone in this. But whether you care for them or not, creepy crawlies will find you, and, particularly if you spend any time outside or have pets, one common creepy crawly that you will deal with is ticks. 

Ticks are important to understand and control because not only are they nuisance parasites of domestic animals and people but they also are capable of carrying and transmitting, that is, being a vector, for a number of diseases. Plus they can also directly cause illness. There are regional differences around the U.S. as to what tick is a possible vector for what disease in that area, however it is important to note that these are not static boundaries. A number of tick species have been documented to be increasing their geographic range and frequency of occurrence.

The Palouse region currently does not have the Ixodes species of tick, which is the intermediate host for Lyme disease. However, on the west side of the Cascades, Ixodes pacificus tick is present, which can be a vector for Lyme disease. We do have several ticks of the Dermacentor species present and Rhipicephalus sanguineous, the Brown Dog Tick has been reported. These tick species have been demonstrated to be vectors for a number of human and animal diseases.

Of course, it is important to know that not every tick is infected and not every tick bite transmits disease. However, a rule of thumb is that the longer an infected tick stays attached to a host, the greater the likelihood of it transmitting disease. The less time you or your pet stay in contact with this bloodthirsty parasite, the better.

In addition to transmitting disease organisms, ticks can themselves cause a disease called tick paralysis. The female ticks of a number of species (including Dermacentor) produce a neurotoxin and the signs are seen 5 to 7 days after the tick has attached. This toxin causes an ascending paralysis—first the hind legs are affected and then it progresses forward with difficulty walking and eventually causes paralysis of the muscles involved in breathing. Any host, from llamas to one report I found about a human child in Washington State, can be affected. Removal of the tick brings a rapid reversal of signs. Dr. Bill Foreyt, parasitologist at Washington State University warns that people with longer hair are at higher risk because it is harder to see the attached ticks.

The best defense against ticks is a good offense. Use repellants and when you return from the outdoors, check yourselves, your children and pets. Be sure to recheck a day later in case you missed a tick that has now become attached. If you find an attached tick, it is recommended that you use tweezers to grasp the tick gently near its head and pull it out. Try to not crush the tick during removal and avoid contact between skin and any fluids from the tick. Then wash your hands with soap and water.

Because pets can carry the ticks into our living spaces, consider using a flea and tick product that both repels and kills ticks if they attach and feed on your pet during the spring and summer months. None of these are 100 percent effective but some have been shown to work quite well. The most safe and effective treatments are currently available through veterinarians, so check with yours for recommendations. 

Letter from the Land:
Life from a Tick's Point of View

by Suvia Judd, from the August 2006 Newsletter

"Ick, tick!" I feel a little "tickle" in my scalp; just some leaf or twig from my walk on the mountain, I think. I pick it out with my fingertips. It wiggles, and I look and see the flat body and eight tiny moving legs of a tick. Now the nerve endings all over my body are on alert, and I pat myself down and pull back my clothes. Fortunately, I don't seem to attract ticks a whole lot. According to Dr. Glen Scoles, a USDA tick researcher, ticks do seem prefer some people to others.

Ticks are arachnids, cousins of spiders. In the Moscow area we have three species of ticks. The Rocky Mountain wood tick, Dermacentor andersonii, is a native tick species whose adults are out looking for a blood meal in late spring and early summer.

A relative with a similar lifecycle is the American Dog tick, Dermacentor variabilis. The third tick, Dermacentor albapictis, commonly called the winter tick or moose tick, is seen feeding on large animals in late winter.

Rocky Mountain wood ticks are first noticed in late spring as adults begin seeking out large animal hosts. Humans, dogs, and farm and wild animals are all host candidates. (Ticks have organs on their front legs that sense carbon dioxide, host odors, and the heat of warm-blooded animals.) The female tick crawls around on the host and finds a good place to attach, a behavior called "questing." It sinks in its mouthparts, and secretes a semihard "tick cement" to hold it in place. The female must feed for seven days; in fact, neither male nor female ticks are able to pull out in response to an adverse stimulus.

When a female wood tick attaches and begins to feed, biochemical changes follow which allow it to expand to contain its meal. When partially fed, the female begins giving off pheromones that attract the males. Male ticks need a smaller blood meal, which gives them energy and triggers the transformation of the sperm into a mobile, ready-to-fertilize form. The males attach and feed for a couple of days, and then, as they sense the pheromones of the females, they begin wandering over the host looking for mates. Mating occurs while the female is attached to the host, and may occur with multiple males. The female keeps feeding, dropping off at seven days to lay her eggs. Males, after the one feeding, may mate multiple times, hanging out around for weeks before they drop off and die.

Meanwhile, the eggs hatch and the larvae attach to a small mammal like a mouse or a squirrel. After a single blood meal, a larva drops off, and the meal triggers the molt into a nymph. If a nymph finds a host by fall, it has a meal, drops off, molts into an adult, and the adult overwinters in the soil. If unfed, the nymph overwinters in the soil and finds a host and transforms in the spring.

American Dog ticks in our area are seen around residences with dogs. Non-natives, they are arriving on dogs from East of the Rockies or from the California coast. They tolerate hotter, drier sites than wood ticks, and numbers of questing adults peak a few weeks later. Adapted to dogs, they also feed on humans and small to medium sized animals.

Winter ticks, also called moose ticks, are dormant all summer, aestivating as tiny larvae in the duff on the ground. In mid to late fall they seek out large hosts like horses or moose, climb on a grazing muzzle, and settle in for the winter. They spend all winter on one animal, having a blood meal before each lifecycle event.

In late winter adults mate, and the females drop off and lay eggs, which hatch and "oversummer" as larvae. Sometimes horses are seen covered with engorged moose ticks in February or March. Moose  populations may suffer die-offs, as animals with thousands of ticks succumb during this season of scarce forage.

So who eats ticks? Their biggest predators are probably ground-feeding birds, including pheasants, quail, grouse, turkeys, robins, towhees, etc. Parasitic wasps use tick larvae in some regions. And in places in the south, Dr. Scoles tells me, the alien fire ants have completely wiped out ticks!

Thanks to Glen Scoles, Bill Foreyt, Ed Bochinski, and Tiege Ulschmid, and a little book by Roger Drummond.

Suvia Judd acquires her ticks mostly on Moscow Mountain.

Copyright: Copyright on articles, recipes and images are jointly held by the Moscow Food Co-op and the respective contributors, except were otherwise noted.

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