"Nature Guide Journal"
26 July 2001
Too smooth to be a burr, the lump in my dog's fur last week turned out
to be a tick. I was a little surprised: I rarely encounter ticks on family
members and the dog stays in our fenced yard.
More than a dozen kinds of hard ticks are found in Oregon, and a few
species of soft ticks. "Hard ticks" are the tiny, familiar
watermelon-seed-shaped arthropods (jointed animals) we find creeping up
our socks or engorged on our pets or game. While hard ticks lurk in tall
grasses and on low shrubs, soft ticks are more likely to hang out in
animal dens and bedding. Both groups of ticks are not insects, but
relatives of spiders.
Hard ticks have three life stages: larva, nymph, and adult. Oddly,
ticks have six legs as larva, but have eight legs as nymphs and adults.
At each stage, the tick "quests" (hangs out on vegetation) to
snag a vertebrate host. Catching hold of a host, the tick typically hangs
on until the host is at rest, then crawls to a suitable location–on
people, a warm, moist place, often at a limb joint, a hairline, or at the
edge of clothing. Attached firmly by harpoon-like mouthparts and glue, the
feeding tick will engorge with up to 600 times its unfed weight in blood.
Hard ticks feed on a blood meal only once at each stage, then drop off
and can remain passive in leaf-litter or vegetation for several months
between stages. In cold climates, it may take as long as three years for a
tick to go through all the three stages.
As with mosquitoes, ticks need a blood meal to develop eggs. A female
hard tick completes her last blood meal then drops to the ground to lay a
single batch of thousands of eggs.
Ticks tend to be picky: about half of Oregon's tick species are found
only on birds, and most of the rest are partial to small mammals.
Pinhead-sized, tick larva typically latch onto smaller animals, with the
nymph and adult of the same species usually going for larger animals.
Only four Oregon ticks are commonly found on people: the western
black-legged tick (Ixodes pacificus), sometimes also called a deer
tick; Rocky Mountain wood tick (Dermacentor andersoni); American
dog tick (Dermacentor variabilis); and the Pacific Coast tick (Dermacentor
occidentalis).
Ticks carry more diseases than any other arthropod—including
mosquitoes. Although only 1%-5% of western black-legged ticks carry Lyme
disease, the severity of this debilitating illness makes avoiding the bite
of these fascinating animals worth the effort.
Since ticks don't pass on the pathogens they carry until they've been
feeding for some time, removing a tick as soon as possible will decrease
your chances of contracting tick-borne disease. People traipsing through
tall grass and brush should carefully check for ticks every several hours.
Using the buddy system helps, as ticks may hide and attach in out-of-sight
places. Wearing light-colored clothing also makes crawling ticks easier to
see.
Imbedded ticks should always be removed by gently pulling it straight
out with a pair of tweezers placed as close to the head of the tick as
possible. Squeezing the tick with your fingers can cause contaminated
fluids to gush out of the tick. Likewise, suffocating or burning a tick
can cause it to disgorge infection-causing fluids.
Notify your doctor if you develop a rash, fever, headaches, or flu-like
symptoms after a tick bite.
Finding a tick on my dog in July should not have been a surprise:
Oregon Health Division reports this month is the high season for the onset
of tick-borne disease in our state. Let hikers and walkers beware.
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For more information:
Dr.
Vredevoe
