Colorado Ticks and Tick-Borne Diseases

The following information from Colorado State University was written about ticks in Colorado, so please consult with your local county extension agent to determine the species of ticks that are prevalent in your area.Keep in mind that many ticks carry diseases that are of importance to horses, so ask your veterinarian if you find multiple ticks on a horse that subsequently develops a fever or other signs of illness.

Quick Facts…

  • In Colorado, Rocky Mountain wood tick and American dog tick are the most common ticks associated with people.
  • Colorado tick fever is by far the most common tick-transmitted disease of the region. Despite its name, Rocky Mountain spotted fever is quite rare in Colorado.
  • No human cases of Lyme disease have originated in Colorado.
  • DEET is the most effective tick repellent. Apply it to pants or other areas of the lower body.
  • To remove a tick, grasp it with blunt tweezers, as close to the skin as possible.

Ticks are blood-feeding parasites of animals found throughout Colorado. They are particularly common at higher elevations. Problems related to blood loss do occur among wildlife and livestock, but they are rare.

Ticks are most important because they can transmit diseases such as Colorado tick fever, Rocky Mountain spotted fever, tularemia and relapsing fever. Lyme disease is an important tick-borne disease in much of the eastern United States. Fortunately, ticks known to transmit it are not known to occur in Colorado, and no confirmed cases have originated in the state.

Some 30 species of ticks occur in Colorado. The table below lists the more common ones. Hard-shelled ticks (Ixodidae family) predominate and are represented by such familiar species as the Rocky Mountain wood tick, American dog tick and brown dog tick. Hard-shelled ticks have a distinctive plate on the back just behind the head. At each stage of development, the tick attaches itself to a host, feeds for several days, becomes extremely bloated, then drops off the host.

Soft ticks (Argasidae family) are much less commonly encountered. They usually are found in the nests of their animal hosts. They tend to feed intermittently, but repeatedly, for only a few hours at a time. One exception is the spinose ear tick, rare in Colorado, that feeds for several months while attached to a large mammal host.

Life Cycle of Ticks

Almost all human encounters with ticks involve either the Rocky Mountain wood tick or the closely related American dog tick. They have a typical life cycle that involves four distinct stages: egg, tiny six-legged larva or seed tick, nymph and adult.

Rocky Mountain wood ticks and American dog ticks are typical of a three-host tick. During each feeding stage (larva, nymph and adult), the tick must find and feed on a different animal, because the tick drops from the host after the blood meal. Females lay their eggs on the ground. The newly hatched larvae seek a small mammal, such as a rodent, as the first host. After feeding, they drop to the ground and molt to the nymph stage. The nymph then seeks its own small mammal host. After feeding this second time, the nymph drops from the animal and molts to the adult stage. Adult Rocky Mountain wood ticks and American dog ticks then feed on a large mammal host, such as a dog or deer. After this feeding, the adults drop off the host and mate, and the females lay eggs. It is the adults that occasionally feed on people.

Ticks are highly sensitive to carbon dioxide, which is exhaled by animals as they breathe, and seek it out. They often are poised at the top of vegetation so they can readily cling to passing animals.

A complete life cycle for these and other multi-host ticks may take from a few months to several years to complete. Its length is mostly determined by how successful they are in locating new hosts. They are highly resistant to starvation and, if necessary, can survive several years without feeding. The common species are most active in late spring and early summer. If the tick has not found a host by the time that hot summer temperatures arrive, it seeks cover under leaves and remains dormant until the next year. Peak periods of tick activity can begin as early as March during warm seasons. They usually subside by mid-July.

A multihost tick with a somewhat different life history is the brown dog tick. This tick can breed continuously indoors and may feed repeatedly on a single (dog) host during each of the three development stages.

Avoiding Ticks

Avoid Tick Habitat

Avoid traveling through areas where ticks are abundant. Ticks are most active in spring and early summer and concentrate where their animal hosts most commonly travel. This includes brushy areas along the edges of fields and woodlands or commonly traveled paths through grassy areas and shrublands.

Use Tick Repellents

There are a few effective tick repellents. By far the most common is DEET (N,N-diethyl-metatoluamide), the active ingredient in most common insect repellents, such as Cutters and Off!. Apply DEET directly to the skin or to clothing. Repellents are most effective if applied to pants and other areas of the lower body likely to come into contact with ticks. DEET can be an effective repellent for ticks as well as other biting arthropods, such as chiggers and mosquitoes. However, the following precautions are encouraged:

  1. On children, do not use high concentration formulations (above 30%).
  2. Apply the repellent to clothing, rather than to skin.
  3. Do not apply DEET to hands or other areas that may come into contact with the mouth.
  4. Do not apply to wounds or irritated skin.
  5. After use, wash or bathe treated areas, particularly on children.

Permethrin (Permanone) is a new tick product. Apply it only to clothing, not to skin. It can kill ticks rapidly. Permanone also may have some repellent activity against ticks.

Wear Protective Clothing

Long pants, long-sleeved shirts and other clothing can help exclude ticks or keep them from attaching to the skin. Ticks are usually acquired while brushing against low vegetation, so pulling socks over the bottom of the pants leg also is useful. Light-colored clothing can make it easier to find ticks that have been picked up.

Conduct Tick Checks

Ticks take several hours to settle and begin feeding. This gives you ample time to detect and remove them. The Rocky Mountain wood tick typically takes 12 to 24 hours to start feeding. Therefore, a thorough “tick check” can be an effective alternative to repellents. After walking through areas where ticks might be present, carefully look for and remove any ticks you may have picked up.

Controlling Brown Dog Ticks in a Home

Unlike the more common ticks (American dog tick, Rocky Mountain wood tick), the brown dog tick spends most of its life around the dog host. It is a subtropical species that cannot survive outdoors year-round in Colorado. Infestations most often develop in protected areas, such as kennels. After they have taken a blood meal, adult ticks may crawl up walls and lay eggs in cracks and corners of the room.

Treatment of the dog is essential, using one of the many flea and tick powders, dips or collars. However, areas that the dog frequents, such as bedding and resting areas, also need to be treated to kill residual ticks. Vacuum cracks along baseboards where ticks may hide and spot treat these areas with insecticide. Discard the vacuum bag and contents after treatment.

If possible, wash bedding and all other materials. Because these ticks are sensitive to cold, storing infested items outdoors during very cold temperatures also can kill these ticks. It may take several weeks and multiple treatments to eliminate brown dog ticks.

How to Remove a Tick

Once a tick has become firmly attached to the skin, removal can be difficult and should be done with care. The mouth parts are barbed, so they may remain after removal and allow infection. Fortunately, the Rocky Mountain wood tick, the most common species found in Colorado, is relatively easy to remove because it has fairly short mouth parts. The recommended procedure for removal of ticks is:

  1. Grasp the tick with blunt tweezers, as close to the skin as possible. If tweezers are not available and you must use your fingers, cover them with tissue or thin plastic to avoid the possible transmission of any disease organisms, such as tularemia, that the tick may harbor.
  2. Pull the tick slowly and steadily, straight away from the skin. Try not to crush the tick as you remove it.
  3. After the tick is removed, treat the feeding site with a disinfectant. Wash your hands when done.

Many other methods have been popularized to remove ticks, such as covering them with petroleum jelly or touching them with a hot match. These methods are not effective.

A rare but potentially serious condition from tick feeding is tick paralysis. This occurs when certain ticks (in Colorado, particularly the Rocky Mountain wood tick) remain attached for a long period and produce an ascending paralysis. Early symptoms, such as difficulty walking, progress to more generalized symptoms, such as limb numbness and difficulty breathing. This condition is completely reversible when the tick is removed.

This article was written by W.S. Cranshaw and F.B. Peairs, Colorado State University Extension entomologists and professors, bioagricultural sciences and pest management.

For more articles visit Colorado State University Extension.






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