CDC

Colorado Tick Fever

Article
Diseases & Conditions
Infectious Diseases
Contributed byKrish Tangella MD, MBAFeb 24, 2020

What are the other Names for this Condition? (Also known as/Synonyms)

  • Arbivorous causing Colorado Tick Fever
  • CTF (Colorado Tick Fever)
  • Mountain Fever caused by Colorado Tick Fever Virus

What is Colorado Tick Fever? (Definition/Background Information)

  • Colorado Tick Fever (CTF) is an acute viral infection caused by Colorado tick fever virus, a member of the genus coltivirus, belonging to the family of Reoviridae
  • The disease is transmitted by bite of an infected tick, specifically the Rocky Mountain wood tick, called Dermacentor andersoni. This tick is only found in certain regions of the United States and Canada. It usually sticks to the host, once the ticks attach themselves to the host’s body
  • The infection usually spreads in the hottest summer months, especially between the months of April to June. CTF is identified by a two-staged fever that continues for 3 days, then diminishes and returns again, for another 1-3 days
  • CTF is generally not a serious condition and the period of signs and symptoms last only for a few weeks, unless any complications develop
  • The treatment of Colorado Tick Fever is symptomatic and the prognosis is excellent in most cases. Currently, there are no vaccines available to prevent this vector-borne infection

Who gets Colorado Tick Fever? (Age and Sex Distribution)

  • Any individual of any age can be affected by Colorado Tick Fever viral infection, if they are bitten by an infected tick
  • Overall, young men and campers are infected the most
  • The ticks that transmit American Mountain Tick Fever are typically blood-feeding parasites of animals in the Rocky mountain region of western United States, as well as Canadian provinces of British Columbia and Alberta. These ticks usually cause blood-related problems in animals and livestock. Hence, almost all incidents of CTF are confined to these geographical regions

What are the Risk Factors for Colorado Tick Fever? (Predisposing Factors)

The risk factors for Colorado Tick Fever include:

  • Living, staying, or traveling to the Rocky mountain areas (the endemic regions) of US and Canada; especially, in the summer months is a major risk factor
  • Trekking, camping, climbing these mountains at elevations 4,000-10,000 feet (most cases are observed at these elevations)
  • Any individual, who comes into contact with the infected ticks
  • Rarely, due to contaminated blood transfusions

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Colorado Tick Fever? (Etiology)

  • Colorado Tick Fever is a tick-borne infection that is caused by the Colorado tick fever virus (CTFV)
  • The major carrier of this virus is the Rocky Mountain wood tick, which is mostly found in the US (Colorado and certain other adjoining states) and Canada
  • Humans usually contract the condition, through the bite of an infected tick. The virus is also carried by small animals, like rats, squirrels and chipmunks
  • There have been some rare cases, where the virus has spread through blood transfusion
  • This acute viral infection is usually common in the summer seasons, generally observed between the months of March to September

What are the Signs and Symptoms of Colorado Tick Fever?

The first signs of Colorado Tick Fever are usually noticed 6 days after initial tick bite. In some cases, the incubation period can be, as long as 20 days. The infected individuals experience 2-stages of fever. The initial episodes of fever prolong for 3 days, which then diminish. The symptoms get better only for the fever to recur a few days later (also called saddleback fever).

Other common signs and symptoms of the condition are:

  • Fever with chills, headaches
  • Pain behind the eyes, light-sensitivity
  • Muscle pain, generalized malaise
  • Abdominal pain
  • Neck stiffness
  • Vomiting and nausea
  • Pimple-like rashes (faint and occasional) caused by focal hemorrhage on the skin

How is Colorado Tick Fever Diagnosed?

A diagnosis of Colorado Tick Fever may involve:

  • Complete physical examination with medical history evaluation (including any recent travel, camping details, if the physician suspects the condition based on its presentations)
  • Blood tests may be performed to detect the virus
  • Complete blood count (CBC)
  • Liver function tests (LFT)
  • CSF analysis may show increased white blood cells to increased protein
  • Polymerase chain reaction (PCR) test on blood may help in the diagnosis too

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Colorado Tick Fever?

Colorado Tick Fever, if left untreated, may severely affect the body systems and organs, causing the following complications:

  • Encephalitis (inflammation of the brain)
  • Aseptic meningitis (inflammation of the meninges, which cover the brain)
  • Hemorrhagic fever
  • Hepatitis (liver inflammation)
  • Lung infection (pneumonia)
  • Myocarditis (inflammation of heart)
  • Prolonged muscle weakness
  • Rarely, the infection can cause death, especially in children

How is Colorado Tick Fever Treated?

Currently, there is no definitive treatment available for Colorado Tick Fever; the treatment is usually symptomatic. However, the infection is self-limiting in most cases, unless any complications arise.

  • The tick should be completely removed from the body and after that analgesics, such as acetaminophen may be administered to relieve of any pain and fever
  • If the individual is dehydrated, then IV fluids may be needed
  • Generally, if signs and symptoms are noted, the affected individuals should visit a healthcare provider, as soon as possible. Hospitalization may be necessary with severe complications
  • Children should not be given aspirin, since certain viral infections can lead to Reye’s syndrome in them
  • Salicylates should not be given, due to the risk of thrombocytopenia (decrease in number of platelets in blood)

How can Colorado Tick Fever be Prevented?

A few preventive measures for Colorado Tick Fever include:

  • Avoid tick-infested regions, mainly during the summer months
  • If you are travelling or visiting such tick-infested areas, then wear light-colored clothes so that the ticks may be easily spotted. The dresses worn should be long-sleeved and with full pants, covering ones’ arms and legs to prevent tick bites
  • Walk in the center of trails, to protect yourself from overhanging bushes/grass
  • Ticks are usually found in the underarms, thighs, and legs; thus, the clothes (and your body) should be checked very often, while in tick-prone areas. The ticks, if any attached or found, have to be removed immediately
  • Individuals, who have been diagnosed with CTF, should not donate blood for a period of 6 months
  • Use of insect repellents with DEET on skin and permethrin on clothing is very effective to control tick bites
  • An individual acquires lifelong immunity to the virus, once infected. However, prevention of tick bites is very important
  • Currently, there are no vaccines available to prevent Colorado Tick Fever

What is the Prognosis of Colorado Tick Fever? (Outcomes/Resolutions)

  • Colorado Tick Fever is usually self-limiting and the prognosis excellent, even when patients have severe neurological problems. In most cases, the symptoms do not last for more than 10 days, and children recover faster (within a week or so)
  • Only in very rare cases do individuals suffer from thrombocytopenia (decrease in platelets in blood) and disseminated intravascular coagulation (clotting of blood). There have been reports of some fatalities, with severe complications

Additional and Relevant Useful Information for Colorado Tick Fever:

  • Steps for tick removal:
    • Grasp the tick by its head, right at the point where they enter the skin, using a pair of pointed tweezers (it is the best method to use)
    • Pull firmly and steadily in an outward direction. Do not twist or squeeze the tick, or apply any other product on the skin
    • Place the tick in a jar containing alcohol to kill the tick
    • Clean the bite wound using a disinfectant
  • Colorado Tick Fever should not be confused with Rocky Mountain spotted fever (RMSF). RMSF is different from CTF. In fact, sometimes both CTF and RMSF may be present together causing confusion in diagnosis. This is known as co-infection with RMSF
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Krish Tangella MD, MBA

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