Utah Pests News Summer 2010

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Ticks and Associated Diseases Occurring in Utah

Moisture from spring rains and snowmelt creates environmental conditions conducive for tick activity in many Utah mountain ranges.  Traveling into the canyons this time of year could result in a tick encounter.  The Rocky Mountain wood tick (Dermacentor andersoni) (Fig. 1) and American dog tick (D. variabilis) (Fig. 2) are the most frequently encountered ticks found feeding on people in Utah.

rocky mountain wood tick
Fig. 1. Rocky Mountain wood tick (female, left, male, right).

American dog tick
Fig. 2. American dog tick (female, left, male, right).

tick mouthparts (hypostome)
Fig. 3. Tick mouthparts (hypostome) showing the barbs which make ticks difficult to remove. Ticks also emit “cement” around the hypostome during feeding that helps them stay in place.

Most tick submissions to the UPPDL occur in May and June, but due to extended moisture this year, high tick activity may occur into mid-summer.  Ticks, in the order Acari, are closely related to other arachnids such as spiders, mites, and harvestmen.  Ticks have eight legs and no wings.  They appear to have one body segment (Figs. 1, 2), which contains the head, abdomen, legs and large mouthparts that project forward from the head.  One key feature of the mouthparts that makes ticks so difficult to remove is the barbed hypostome (Fig. 3).

The tick life cycle consists of four stages:  egg, larvae (only six legs), nymph, and adult.  Dermacentor ticks require three unique hosts throughout their life.  Ticks find new hosts by a process called questing, whereby they climb to the top of vegetation and extend their legs when they sense a host approaching (Fig. 4).  If the host contacts them, they latch on and search for a suitable feeding site.  After each feeding, the tick will fall from its host to the ground where it will molt and wait for another host to pass by.  Generally, these consist of a small animal or rodent for the larva stage, a medium-sized animal for the nymph stage, and a large animal, such as cattle, dogs, or humans, for the adult stage.  Feeding ticks greatly increase in size during the feeding process (Fig. 5).   Adults mate and feed on the final host.  The female falls to the ground, digests her blood meal, and can lay over 4,000 eggs (Fig. 6).

american dog tick questing on a blade of grass
Fig. 4.  An American dog tick questing on a blade of grass.

tick engorgement
Fig. 5.  Rocky mountain wood tick showing multiple stages of engorgement.

winter fern tick laying eggs
Fig. 6.  Female winter fern tick (Dermacentor albipictus) laying eggs.

Three-host ticks normally take 2-3 years to complete development, completing one molt or more per year depending on conditions and questing success.  Since ticks are mostly passive in their host finding, they may or may not readily find new hosts.  Ticks can survive extended periods without feeding.  Larvae can survive for a few months, nymphs for over half a year, and adults can survive for over 2 years without a blood meal.  If a host is not located before mid-summer, ticks will retreat to the leaf litter until the following spring when favorable conditions prevail.

While there are about 12 species of Dermacentor ticks in North America, two closely related species of ticks are responsible for most human bites in Utah, the Rocky Mountain wood tick and American dog tick.  Unfortunately, ticks have the ability to vector viral and bacterial pathogens which may cause serious human and animal diseases.  In fact, ticks are second only to mosquitoes in transmitting disease to humans.  Being closely related, the Rocky Mountain wood tick and American dog tick transmit many of the same diseases (Table 1).  Ticks contract diseases from hosts, and then can carry them through successive molts or transmit them to offspring.


Table 1.   Bacterial, viral, and toxic-based diseases vectored by American dog tick (ADT) and Rocky Mountain wood tick (RMWT). 
Cause Vector Type Symptoms
Rocky Mountain spotted fever Rickettsia rickettsi RMWT; ADT bacteria sudden onset chills and fever, headache, blood-shot eyes; leakage of blood from capillaries over the entire body
Q-fever Coxiella burnetti RMWT; ADT bacteria fever, headache, chills, weakness, malaise, severe sweating
Tularemia Francisella tularensis RMWT; ADT bacteria chills, fever, prostration, ulceration at bite location, and tender, swollen lymph nodes
Colorado tick fever Orbivirus RMWT; ADT virus sudden onset, intermittent fever, headache, muscular pain, leukopenia
Powassan encephalitis Flavivirus RMWT virus occurs 7–10 days after bite; fever headache, partial paralysis, confusion, nausea, coma
Tick paralysis saliva toxin RMWT; ADT neurotoxin paralysis spreading from feet to upper regions of body; may cause death

Immediately consult a doctor if you have been fed on by a tick.  Early detection of a pathogen could lead to a quick recovery, and a reduction/elimination of chronic health problems.  Tick paralysis (TP) is a condition caused by the feeding of some ticks.  Saliva injected into the human body during feeding causes paralysis which starts at the feet and moves up the body.  In severe cases, TP can cause respiratory failure and death.  Mortality from TP occurs most frequently in children under 7; adults are rarely paralyzed by ticks.  Fortunately, the paralysis is fully reversible by removing the tick.  Always complete a thorough “tick-check” after leaving tick habitat.  Dermacentor ticks may take at least 2 hours to find a suitable feeding site and even longer to get mouthparts into skin to feed.  Transmission of disease usually occurs 12 hours after feeding has begun.

Proper tick removal is simple, but requires the use of forceps or tweezers.  There are many suggested methods for tick removal, but to greatly reduce your chance of contracting a tick-borne disease, there is only one proper removal method, as outlined by Intermountain Health Care:

For larger hard ticks:

  • Use tweezers and grasp the tick as close to the skin as possible, targeting the mouthparts.  If tweezers are not available, use a loop of thread around the mouthparts or a needle between the mouthparts.
  • Carefully pull the tick straight upward without twisting or crushing it.  Use steady pressure until it releases.  Crushing or squeezing a tick can cause it to regurgitate stomach contents into your blood stream, which can transmit tick-borne diseases.

For smaller hard ticks:

  • Scrape the tick with a knife blade or credit card edge, being careful not to cut yourself.
  • Place tick in a sealed container and have it identified.

General treatment:

  • If the head accidentally breaks off and remains in your skin, clean the area around the bite and use a sterile needle to carefully lift or scrape the head from the skin.
  • Wash the wound and your hands with soap and water after removing the tick.  Apply an over-the-counter antibiotic ointment to help reduce the chance of catching a tick-borne, or secondary infection.

Consider these tips to avoid coming in contact with ticks.

  • Avoid grassy and bushy areas along edges of woodlands and fields, from March to mid-July.
  • Apply tick repellent to clothing before entering tick habitat.
  • Wear long pants and long-sleeved shirts.  Tuck shirts into pants and pants into socks.
  • Wear light-colored clothes to make it easier to detect and remove ticks.
  • Conduct tick checks everywhere on your body, including armpits, waistline, belly button, scalp and crotch areas.

Based on data collected 20 years ago, Lyme disease-carrying ticks are not believed to exist in Utah.  However, Utah is home to the black legged tick (Ixodes pacificus), which is a carrier and vector of the disease in other states.  This tick is much smaller than the Dermacentor ticks commonly encountered in Utah.  Given recent increasing reports of Lyme disease in Utah, the Center for Disease Control (CDC) is trying to determine the status of Lyme disease here.  Regardless, always practice sound tick avoidance and thorough tick checks to avoid contracting tick-borne diseases of any kind.  Remember, different ticks carry different diseases, so be sure to collect any tick that has bitten you, and have it identified by the Utah Plant Pest Diagnostic Lab.

-Ryan Davis, Arthropod Diagnostician


Cranshaw, W.S., and F.B. Peairs. 2010. Colorado Ticks and Tick-Borne Diseases.  http://www.ext.colostate.edu/pubs/insect/05593.html.
Larisa, V. 1997.  Ticks Commonly Encountered in California.  Department of Entomology, University of California, Davis. http://entomology.ucdavis.edu/faculty/rbkimsey/caticks.html.
Schmitt, B.D., and D.A. Thompson. 1994-2010.  Tick Bite – Children: Self-Care Decisions LLC.  http://intermountainhealthcare.org/HEALTH/SYMPTOM/Pages/TickBite-Children.aspx.
Yunker, C.E., et al. 1986. Dermacentor ticks (Acari: Ixodoidea: Ixodidae) of the New World:  A Scanning Electron Microscope Atlas. Proceedings of the Entomological Society of Washington. 88(4), pp. 609-627.