Colorado tick fever is an uncommon viral disease you can get from a Rocky Mountain wood tick bite. This virus originally infects small animals like squirrels, chipmunks, and mice. Ticks get infected by biting these small animals and can then pass the infection on to you if they bite you. This disease is usually mild, but it can cause severe complications.
What Is Colorado Tick Fever?
Colorado tick fever is also known as mountain fever and mountain tick fever. Ticks that live in the western U.S. spread this disease. If you get infected, you're likely to become mildly ill, experiencing muscle aches, fever, and headaches. You can typically expect to recover within a week, though some cases last longer.
The Colorado tick fever virus is a double-stranded RNA virus belonging to the coltivirus family. Colorado tick fever is most common in the Rocky Mountain area in the U.S. Rocky Mountain wood ticks (Dermacentor andersoni) transmit it to humans through their bites.
Wyoming reports the most cases in the U.S. Colorado tick fever is also common in Colorado, Idaho, Montana, Oregon, and Utah. These six states report 80% of all cases in the U.S. Most cases will occur between May and July. Fewer than 10 cases are reported in the U.S. each year, though it is believed that more go undiagnosed. Additionally, this disease has been reported in the Canadian provinces of Alberta and British Columbia.
The Colorado tick fever virus stays in the bloodstream for several months, meaning that it can be transmitted by blood transfusions and bone marrow transplants. If you've had this illness, you shouldn't donate bone marrow or blood for at least 6 months. Outside of these donations, the virus is not passed from person to person.
Colorado Tick Fever Symptoms
Symptoms manifest within two weeks after you were bitten by a tick. The usual symptoms include:
- Fever
- Chills
- Headache
- Malaise
- Muscle pain
- Abdominal pain
- Sore throat
- Vomiting
- A rash
You may experience general weakness and feel tired for a long time. Colorado tick fever is also often biphasic — you may have two periods of illness separated by a few days when you feel better. This pattern of illness is sometimes called "Saddleback fever" and happens in about half of people with this disease.
Complications are rare but can include meningitis (inflammation of the membranes covering the brain), encephalitis (inflammation of the brain), pericarditis (inflammation of the membrane surrounding the heart), myocarditis (inflammation of the heart muscle), pneumonia, or a coma.
Most people recover from Colorado tick fever. Life-threatening disease and death are rare. Children, though, can develop bleeding disorders leading to death. Older people with other medical disorders are also at risk for severe disease and death.
Colorado Tick Fever Diagnosis
Your doctor will correlate your symptoms with your location or recent traveling. Your activities, occupation, and likelihood of tick exposure will all be factored in. Your doctor may also send samples for laboratory testing, including methods such as:
- Viral RNA detection
- Antibody tests. The results of these tests may not be conclusive for up to 14 to 21 days.
- Reverse-transcriptase polymerase chain reaction (RT-PCR). These results are likely to return more quickly than those of antibody tests.
If such laboratory tests are not available locally, your doctor may have to send your specimens to the Centers for Disease Control and Prevention (CDC) Arbovirus Diagnostic Laboratory.
The symptoms of Colorado tick fever are similar to those of Lyme Disease and Rocky Mountain Spotted Fever. Like Colorado tick fever, these illnesses are also spread by ticks. It's important to make an accurate diagnosis, though, because Lyme Disease and Rocky Mountain Spotted Fever are bacterial diseases that require antibiotic treatment.
Colorado tick fever also resembles a tick-borne relapsing fever caused by Borrelia hermsii. This relapsing fever causes several episodes of fever with longer intervals compared to the biphasic fever of Colorado tick fever, which has a first and second phase that are only separated by an interval of one or two days.
Colorado Tick Fever Treatment
There are no medicines that can cure this viral disease. Your doctor will instead prescribe medicines to relieve your fever, muscle pain, and other symptoms. If you have a severe case, your doctor may prescribe intravenous fluids and other supportive treatment.
Colorado tick fever sets in abruptly, and the fever is high. The disease is described as intense, and 31% of people require hospitalization.
Colorado Tick Fever Prevention
There isn't a vaccine available for this viral disease. However, you can keep yourself safe by taking precautions to avoid tick bites:
- Avoid areas known to be tick-infested.
- Ticks lurk on trees, shrubs, and long grass, so stay on clear paths and avoid contact with greenery.
- Wear clothing that covers most of your skin. Trousers and long-sleeved shirts are protective.
- Use light-colored clothes so that you can easily see any ticks.
- Ticks can climb up your legs. Tuck your trousers into your socks to prevent that.
- If you're going into a tick-infested area, treat your clothes, shoes, and camping gear with an insecticide.
Also, apply insect repellent on all exposed skin areas. The Environmental Protection Agency (EPA) registers recommended formulas that contain diethyltoluamide (DEET), oil of lemon eucalyptus, para-menthane-diol, picaridin, or IR3535.
After visiting a tick-infested area, look for ticks on your skin. They tend to be found under your arms, in and around your ears, inside your belly button, between your legs, behind your knees, and around your waist. If you see any ticks on your skin, remove them with tweezers or special instruments. Don't crush or squeeze a tick or apply heat, nail polish, or petroleum jelly. After removing the tick, clean the bite area (if there is one) and your hands with alcohol or soap and water.