Rocky Mountain Tick Fever

This information was taken from a brochure from the Colorado Department of Health plus information form Barbara Martens - RN/Communicable Disease Control Coordinator - for Jefferson County.

What is Colorado Tick Fever?

Colorado Tick Fever (CTF) is an acute viral illness characterized by fever, headache and body aches. Other symptoms may include lethargy, nausea, abdominal pain and rarely a skin rash. Typically the illness lasts four to five days followed by apparent recovery, but then the fever and symptoms recur for another two to three days. Complete recovery usually takes two to three weeks. The disease is rarely life threatening and infected persons are usually resistant to re-infection. There is currently no effective treatment or preventive vaccine available for tick fever.

What Causes It?

From 100 to 300 cases of CTF are reported to the Colorado Department of Health each year. CTF virus, harbored in rodents, infects man through the bite of an infected Rocky Mountain wood tick. Adult ticks begin to emerge in late February or March and seek larger animal hosts including man for a blood meal that is a prerequisite for their reproduction. The virus is transmitted to men when an infected tick attaches and bites through the skin. If virus is transmitted to the victim, illness will usually begin within six days.

Rocky Mountain Wood Ticks

The Rocky Mountain wood tick is a hard tick, about 1/16" long, which may grow to nearly ½" long when engorged. The female is dark reddish brown with a white shield covering the front third of the body. The male has a grayish white shield area on the top of the body. They are found in the mountainous areas of Colorado. Ticks are especially abundant on south-facing brushy slopes of Colorado Mountains, especially east of the Continental Divide.

Who Gets It?

Hikers are the most likely persons to acquire ticks and become infected with CTF. Campers, fishermen, mountain residents and those who working in or visit the mountains during the months of March through July, or even into early fall, are at risk for exposure to CTF.


"Tick checks" are the cheapest and most effective methods of reducing the risk of CTF according to a study recently completed by the Colorado Department of Health. A tick check is simply the periodic checking and removal of attached and unattached ticks from one's body. These should be performed at two to three hour intervals while outdoors in the mountain environment. Tick checks can be done alone, but are more thorough if a companion or parent helps examine an individual's back and scalp. Tick checks are effective because ticks spend some time on an individual's body before actually transmitting the virus.

An estimated 75 percent of CTF cases could be prevented if everyone in the outdoor environment used this method routinely.

There are two additional ways to reduce the risk of CTF. Treating clothing with insect repellents containing DEET or permethrin can significantly reduce the number of ticks that climb onto the clothing. Avoid areas of thick tick infestations, especially during the months of April, May and June.

How to Remove a Tick

If a tick is found on your body, take hold of the tick with a tissue, disposable glove, or tweezers etc. Gently tug but do not twist or bend back and forth. Do not crush the tick with your bare hands. It could still be lodged in your skin and CTF could still be the result.

Other Tick-Bourne Diseases

Two other diseases in Colorado are primarily transmitted by tick bites: Rocky Mountain Spotted Fever and Relapsing Fever. Although common in some areas of the country, Rocky Mountain Spotted Fever is rare in Colorado. This disease is much more seriouos than Colorado Tick Fever but is fortunately treatable with antibiotics. The name "spotted fever" came from a rash that begins on the extremities and spreads to the rest of the body. It is important that persons who become ill after a tick exposure who develop a rash seek medical treatment immediately.

Relapsing Fever is another tick borne disease, caused by a soft tick, which is a night-time feeding tick usually found in old cabins. This disease characterized by an intermittent series of fevers, is also treatable with antibiotics.

If you get sick consult your physician

Persons who develop a fever after a tick exposure should consult with a physician. Diagnostic tests are available to differentiate CTF cases from treatable and more serious illnesses.

For Additional Information

Contact the Jefferson County Health Department, 260 L. Kipling St., Lakewood, CO 80226, 303-232-6301; the Colorado Department of Health, or your physician for more information about CTF.

Shirley Johnson