Colorado tick fever

Definition

Colorado tick fever is an acute viral infection spread by the bite of the Dermacentor andersoni wood tick.

Alternative Names

Mountain tick fever; Mountain fever; American mountain fever

Causes, incidence, and risk factors

This disease is usually seen between March and September. Most cases occur in April, May, and June.

Risk factors are recent outdoor activity and recent tick bite.

Colorado tick fever is seen most often in Colorado. Up to 15% of campers have been exposed to the virus that causes the disease. The disease is much less common in the rest of the United States.

Symptoms

Symptoms of Colorado tick fever start 3 to 6 days after getting the tick bite. A sudden fever continues for 3 days, goes away, then comes back 1 to 3 days later for another few days. Other symptoms include:

• Generalized weakness
• Headache behind the eyes
• Muscle aches
• Nausea and vomiting
• Rash (may be light-colored)
• Sensitivity to light ( photophobia)
• Skin pain
• Sweating

Signs and tests

Tests are done to confirm the infection. These may include:

• Complement fixation antibody test
• Immunofluorescence antibody test

Other blood tests may include:

• Complete blood count (CBC)
• Creatine kinase
• Liver function tests

Treatment

Make sure the tick is fully removed from the skin. Take a pain reliever if necessary (do not give aspirin to children -- it is associated with Reye syndrome in some viral illnesses). If complications develop, treatment will be aimed at controlling the symptoms.

Support Groups

Expectations (prognosis)

Colorado tick fever usually goes away by itself and is not dangerous.

Complications

Complications include aseptic meningitis, encephalitis, and hemorrhagic fever.

Calling your health care provider

Call your health care provider if you are unable to fully remove a tick embedded in the skin, if you or your child develop symptoms of this disease, if symptoms worsen or do not improve with treatment, or if new symptoms develop.

Prevention

When walking or hiking in tick-infested areas, wear closed shoes, long sleeves, and tuck long pants into socks to protect the legs. Wear light-colored clothing, which shows ticks more easily than darker colors, making them easier to remove.

Check yourself and your pets frequently. If you find ticks, remove them immediately by using a tweezers, pulling carefully and steadily. Insect repellent may be helpful.

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References

Naides SJ. Arthropod-borne viruses causing fever and rash syndromes. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 405.