American Dog Tick

The American dog tick (Dermacentor variabilis) common name comes from the fact that it is only found in North America. While quite likely the most common tick in the Kansas City area, it is found throughout the United States except for the area of the Rocky Mountains, and in Canada and Mexico.

Domestic dogs are the favorite host of the adults. Although not a structural pest, it is commonly brought inside on dogs but will readily attack humans. It is of medical importance because it vectors the causal organisms of several very serious diseases or conditions. American dog ticks are the primary vector of Rocky mountain spotted fever in the eastern United States, which they transmit from small animals. These ticks also transmit tularemia and tick paralysis, both of which require immediate medical attention.

Recognition

We speak of engorged and un-engorged ticks. Engorged means that they have consumed a blood meal. The un-engorged American dog tick adult female is about 3/16" long, with the male being slightly smaller (about 1/8"}; engorged female up to about 5/16" long and 3/8" wide. Their bodies are oval and flattened. Their color is brown with whitish to grayish markings, often with silvery hue. The first immature stage has only six legs, while the remaining immature stages and the adults have eight legs.

Biology

Adults crawl up on grass or other low vegetation and wait for a host to pass. After both sexes have fed, mating occurs on the host. Males continue to feed but females drop off to lay their eggs. Over 14-32 days she lays egg masse totaling 4,000-6,500 yellowish-brown eggs, and then she dies. The entire life cycle (egg to egg) requires 3 months to more than one year, and both larvae and nymphs can overwinter. In the northern states, a 2-year life cycle may be more common.

Habits

The American dog tick does not survive well indoors. If found indoors, it was probably carried in on a dog and dropped off when fully engorged, to seek a suitable place for egg laying.

This is a 3-host tick, with each stage requiring a different host. Both larvae and nymphs actively crawl about seeking a mammalian host, such as the white footed mouse, meadow mouse, cotton rat, cottontail and swamp rabbits, Norway rat, muskrat and squirrel, all of which are common in eastern Kansas and western Missouri. Larvae alone are known from house mouse, jack rabbit, and mole. Nymphs alone are known from the wood rat, sheep, cattle, and dog. Because of this kind of host seeking activity, neither larvae nor nymphs are picked up on tick drags.

Adults crawl up grass or other low vegetation, cling to it with their 3rd pair of legs, and wave their other legs about ready to grasp onto any passing host; this is called their "waiting position." They prefer larger mammals as hosts and the preferred dog and others such as man, cattle, opossum, coyote, hog, horse, raccoon, wild cat, squirrel, sheep, skunk, deer, fox, domestic cat, mule, rabbit, Norway rat, ground squirrel, donkey/burro, weasel, and woodchuck.

American dog ticks are attracted by the scent of animals and are therefore most numerous along roads, paths, and trails. The concentration is further increased along such travel routes by the dropping of engorged ticks from their host animal.

Larval and nymphal activity usually starts about the end of March, representing those which overwintered, and continues to mid-July. Nymphal activity predominates from June to early September. Adults become active about mid-April, peak in June, and decline until mid-September.