Colorado tick fever (CTF) (also called mountain tick feverAmerican tick fever, and American mountain tick fever) is a viral infection (Coltivirus) transmitted from the bite of an infected Rocky Mountain wood tick (Dermacentor andersoni). It should not be confused with the bacterial tick-borne infection, Rocky Mountain spotted fever.

The type species of the genus Coltivirus, Colorado tick fever virus (CTFV) infects haemopoietic cells, particularly erythrocytes, which explains how the virus is transmitted by ticks and also accounts for the incidence of transmission by blood transfusion.


Symptoms of Colorado tick fever may include severe headaches, light sensitivity, muscle aches, skin tenderness, loss of appetite, nausea, vomiting, abdominal pain, fever, weakness, fatigue, muscle pain, chills and rash. These symptoms often begin within 3 to 6 days after a tick bite occurs. This period of time is referred to as the incubation period. Once symptoms develop, they usually go away within 10 days. 


Your doctor can make a Colorado tick fever diagnosis by doing a physical examination and performing various laboratory tests. These tests may include:

Complement Fixation Antibody Test

This test determines whether antibodies to the Colorado tick fever virus are present in the blood. Antibodies are special proteins that help fight off harmful substances, such as bacteria and viruses. If the antibodies to the Colorado tick fever virus are found, then a Colorado tick fever diagnosis is made. 

Complete Blood Count

This is a broad screening test that measures the amount of white blood cells, red blood cells, and platelets in the body. It is a simple blood test that can help doctors determine the exact cause of the symptoms.

Liver Function Tests

These tests evaluate how well the liver is working by measuring levels of proteins, liver enzymes, and bilirubin in the blood. Colorado tick fever can affect the liver, so impaired liver function may be a sign of the disease.


Treatment is rarely required, and most people make a full recovery without complications. The fever and muscles aches may be treated with acetaminophen, such as Tylenol, and other pain relief medications. Getting plenty of rest and staying hydrated are important as well. 

You will also need to remove the tick as soon as possible. Call your doctor if you are unable to remove the entire tick from your skin.

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