Colorado tick fever (CTF) is a self-limiting, often benign, febrile illness spread to humans through infected tick bites [1] [2]. A spurt in CTF cases is usually noticed from April until August as the ticks are active in these months. Ticks get infected with the virus when feeding on the blood of rodents such as mice, squirrels, and chipmunks, and then transmit the virus while feeding on either humans or animals. Rarely, the infection can be transmitted via blood transfusion, but otherwise, person to person transmission has not been reported. The onset of symptoms can occur anytime between 1 to 14 days after the tick bite.

The clinical presentation is non-specific with fever, malaise, myalgias, arthralgias, lassitude, fatigue, sore throat, nausea, or vomiting. A maculopapular rash with palatal spots may be present in some patients. Some patients may have the classic CTF "biphasic" or "saddleback" fever characterized by fever for a few days, followed by improvement in symptoms for the next few days, and then another short phase of fever with constitutional symptoms. A majority of patients have a self-limiting illness and recover without sequelae although the weakness can persist for several weeks. There have been rare reports of central nervous system involvement with meningitis and encephalitis in children [1] [2] [3] [4] [5], as well as in some adults [6]. Other uncommon clinical presentations include photophobia [7], diarrhea, hepatitis, epididymo-orchitis, arthritis, hemorrhagic diathesis, carditis, pneumonia, and even coma [1] [2] [8] [9].

• Splenomegaly

  Splenomegaly may occur. Some patients have altered sensorium or even coma. Complications of Colorado tick fever are unusual and rare. [emedicine.medscape.com]

• Fever

  This disease is caused by infection with the Colorado tick fever virus, a member of the Coltivirus genera. In the past, it has been named Mountain fever or American mountain fever. CTF virus was first isolated from human blood in 1944. [web.archive.org]

  Mountain tick fever; Mountain fever; American mountain fever Bolgiano EB, Sexton J. Tick-borne illnesses. In: Walls RM, Hockberger RS, Gausche-Hill M, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 9th ed. [nlm.nih.gov]

  Ecology of Colorado tick fever. Annu Rev Microbiol. 1988; 42 :49–64. [ PubMed ] [ Google Scholar ] Emmons RW, Oshiro LS, Johnson HN, Lennette EH. Intra-erythrocytic location of Colorado tick fever virus. [pubmedcentral.nih.gov]

  Part Descriptions LP18316-7 Colorado tick fever virus Colorado Tick Fever (CTF) also called (Mountain tick fever, Mountain fever, and American mountain fever) is an acute viral infection transmitted from the bite of an infected wood tick (Dermacentor [loinc.org]

• Chills

  ) Certain infectious and parasitic diseases Clinical Information A febrile illness characterized by chills, aches, vomiting, leukopenia, and sometimes encephalitis. [icd10data.com]

  Symptoms fever headache chills light sensitivity myalgias malaise fatigue and malaise, for weeks to months nausea, diarrhea light sensitivity rare pneumonitis myocarditis hepatitis Signs and tests Complement fixation antibody test Immunofluorescence antibody [whatislyme.com]

  Symptoms generally include acute onset of fever, headache, chills, and myalgias; illness often lasts for 3 weeks or more. [ncbi.nlm.nih.gov]

  The initial symptoms of the disease often include fever, chills, headache, muscular and skeletal pain, and malaise. Other symptoms may include nausea, vomiting, stomach pain, light sensitivity and sore throat. [aldf.com]

  Symptoms of Colorado tick fever include: Fever and chills. Headache, often severe. Muscle aches (myalgias). Sensitivity to light (photophobia). Medical treatment can help relieve the symptoms of Colorado tick fever. [myhealth.alberta.ca]

• Fatigue

  Initial clinical diagnosis of CTF is based on the patient's history of travel to endemic areas with probable tick bites followed by fever and fatigue. [symptoma.com]

  Symptoms fever headache chills light sensitivity myalgias malaise fatigue and malaise, for weeks to months nausea, diarrhea light sensitivity rare pneumonitis myocarditis hepatitis Signs and tests Complement fixation antibody test Immunofluorescence antibody [whatislyme.com]

  […] for a rare disease Colorado tick fever Disease definition Colorado tick fever (CTF) is an acute arboviral infection caused by a Coltivirus transmitted by an infected tick and characterized by a biphasic fever with headache, myalgias, arthralgias, and fatigue [orpha.net]

  People should let their doctors know of any weakness and fatigue lasting several weeks after the tick bite. Prevention Checking pets for ticks is recommended to minimise tick exposure. [medicalnewstoday.com]

• Malaise

  Symptoms fever headache chills light sensitivity myalgias malaise fatigue and malaise, for weeks to months nausea, diarrhea light sensitivity rare pneumonitis myocarditis hepatitis Signs and tests Complement fixation antibody test Immunofluorescence antibody [whatislyme.com]

  Col·o·ra·do tick fever | \ ˌkäl-ə-ˈrad-(ˌ)ō-, -ˈräd- \ : a mild disease of the western United States and western Canada that is characterized by intermittent fever, malaise, headaches, myalgia, and the absence of a rash and is caused by a reovirus (species [merriam-webster.com]

  The initial symptoms of the disease often include fever, chills, headache, muscular and skeletal pain, and malaise. Other symptoms may include nausea, vomiting, stomach pain, light sensitivity and sore throat. [aldf.com]

  Symptoms, which are often non-specific, begin 3 to 5 days after the bite with an abrupt onset of fever and any of these: headaches, chills, malaise, photophobia, myalgias, nausea, vomiting, diarrhea and abdominal pain. [lymediseaseassociation.org]

  Signs and Symptoms Following infection, symptoms that may occur include fever, headache, chills, light sensitivity, muscle aches, malaise, nausea, vomiting, diarrhea, abdominal pain, and rarely a rash. [columbia-lyme.org]

• Biphasic Fever

  Abstract Colorado tick fever (CTF) virus elicits an acute illness in humans, producing nonspecific flu-like symptoms and a biphasic fever in approximately 50% of patients. [ncbi.nlm.nih.gov]

  Homepage Rare diseases Search Search for a rare disease Colorado tick fever Disease definition Colorado tick fever (CTF) is an acute arboviral infection caused by a Coltivirus transmitted by an infected tick and characterized by a biphasic fever with [orpha.net]

  […] presentation Influenza-like illness Rash – uncommon (can be macular, maculopapular, or petechial) In rare cases, life-threatening illnesses (difficulty breathing, hemorrhage, renal failure, neurological problems) or death Influenza-like illness, with frequent biphasic [arupconsult.com]

• Cough

  The typical symptoms include fever, headaches, chills, and muscle aches and sometimes cough and mental confusion. Usually, these symptoms occur within 1-2 weeks after a tick bite. Rashes may occur but are rare. [orkin.com]

• Nausea

  Symptoms fever headache chills light sensitivity myalgias malaise fatigue and malaise, for weeks to months nausea, diarrhea light sensitivity rare pneumonitis myocarditis hepatitis Signs and tests Complement fixation antibody test Immunofluorescence antibody [whatislyme.com]

  In some cases, macular, maculopapular, or petechial rash and/or stiff neck, nausea, vomiting, abdominal pain, diarrhea, and sore throat may also occur. [orpha.net]

  Symptoms, which are often non-specific, begin 3 to 5 days after the bite with an abrupt onset of fever and any of these: headaches, chills, malaise, photophobia, myalgias, nausea, vomiting, diarrhea and abdominal pain. [lymediseaseassociation.org]

  Signs and Symptoms Following infection, symptoms that may occur include fever, headache, chills, light sensitivity, muscle aches, malaise, nausea, vomiting, diarrhea, abdominal pain, and rarely a rash. [columbia-lyme.org]

• Vomiting

  In some cases, macular, maculopapular, or petechial rash and/or stiff neck, nausea, vomiting, abdominal pain, diarrhea, and sore throat may also occur. [orpha.net]

  Symptoms, which are often non-specific, begin 3 to 5 days after the bite with an abrupt onset of fever and any of these: headaches, chills, malaise, photophobia, myalgias, nausea, vomiting, diarrhea and abdominal pain. [lymediseaseassociation.org]

  Signs and Symptoms Following infection, symptoms that may occur include fever, headache, chills, light sensitivity, muscle aches, malaise, nausea, vomiting, diarrhea, abdominal pain, and rarely a rash. [columbia-lyme.org]

  Abdominal pain and vomiting occur occasionally. The first attack lasts about two days. [britannica.com]

• Abdominal Pain

  In some cases, macular, maculopapular, or petechial rash and/or stiff neck, nausea, vomiting, abdominal pain, diarrhea, and sore throat may also occur. [orpha.net]

  Symptoms, which are often non-specific, begin 3 to 5 days after the bite with an abrupt onset of fever and any of these: headaches, chills, malaise, photophobia, myalgias, nausea, vomiting, diarrhea and abdominal pain. [lymediseaseassociation.org]

  Stiff neck, retroorbital pain, photophobia [1], nausea and vomiting, abdominal pain, diarrhea, and sore throat all have been reported in a minority of patients. [emedicine.medscape.com]

  Signs and Symptoms Following infection, symptoms that may occur include fever, headache, chills, light sensitivity, muscle aches, malaise, nausea, vomiting, diarrhea, abdominal pain, and rarely a rash. [columbia-lyme.org]

• Diarrhea

  Symptoms fever headache chills light sensitivity myalgias malaise fatigue and malaise, for weeks to months nausea, diarrhea light sensitivity rare pneumonitis myocarditis hepatitis Signs and tests Complement fixation antibody test Immunofluorescence antibody [whatislyme.com]

  In some cases, macular, maculopapular, or petechial rash and/or stiff neck, nausea, vomiting, abdominal pain, diarrhea, and sore throat may also occur. [orpha.net]

  Symptoms, which are often non-specific, begin 3 to 5 days after the bite with an abrupt onset of fever and any of these: headaches, chills, malaise, photophobia, myalgias, nausea, vomiting, diarrhea and abdominal pain. [lymediseaseassociation.org]

  Signs and Symptoms Following infection, symptoms that may occur include fever, headache, chills, light sensitivity, muscle aches, malaise, nausea, vomiting, diarrhea, abdominal pain, and rarely a rash. [columbia-lyme.org]

• Loss of Appetite

  Symptoms of Colorado tick fever include: fever up to 105°F chills severe headache light sensitivity muscle aches skin tenderness loss of appetite nausea vomiting abdominal pain weakness and fatigue faint rash It’s important to note that symptoms of Colorado [healthline.com]

  The symptoms of Heartland virus are headaches, muscle aches, diarrhea, loss of appetite and nausea. 364D Richettsiosis This disease is found in California and other west coast areas where the Pacific Coast tick is found. [orkin.com]

  The fever may be accompanied by: a headache (usually behind the eyes) chills and sweating sensitivity to light skin or muscle pain malaise (a general feeling of being unwell) extreme fatigue Other symptoms may include: weakness nausea loss of appetite [medicalnewstoday.com]

• Petechiae

  Petechiae occur in rare cases and may be complicated by thrombocytopenia. A palatal enanthema is sometimes present. Nuchal rigidity is found in 15-20% of cases. Splenomegaly may occur. Some patients have altered sensorium or even coma. [emedicine.medscape.com]

• Myalgia

  Symptoms generally include acute onset of fever, headache, chills, and myalgias; illness often lasts for 3 weeks or more. [ncbi.nlm.nih.gov]

  Symptoms fever headache chills light sensitivity myalgias malaise fatigue and malaise, for weeks to months nausea, diarrhea light sensitivity rare pneumonitis myocarditis hepatitis Signs and tests Complement fixation antibody test Immunofluorescence antibody [whatislyme.com]

  Col·o·ra·do tick fever | \ ˌkäl-ə-ˈrad-(ˌ)ō-, -ˈräd- \ : a mild disease of the western United States and western Canada that is characterized by intermittent fever, malaise, headaches, myalgia, and the absence of a rash and is caused by a reovirus (species [merriam-webster.com]

• Arthralgia

  […] diseases Search Search for a rare disease Colorado tick fever Disease definition Colorado tick fever (CTF) is an acute arboviral infection caused by a Coltivirus transmitted by an infected tick and characterized by a biphasic fever with headache, myalgias, arthralgias [orpha.net]

  The clinical presentation is non-specific with fever, malaise, myalgias, arthralgias, lassitude, fatigue, sore throat, nausea, or vomiting. A maculopapular rash with palatal spots may be present in some patients. [symptoma.com]

  Common flulike symptoms include the following: Headache Myalgias Arthralgias Fatigue In addition, a nonspecific evanescent rash may be present (5-15% of cases), sometimes with a palatal enanthema. [emedicine.medscape.com]

• Photophobia

  Sensitivity to light (photophobia). Medical treatment can help relieve the symptoms of Colorado tick fever. Current as of: July 30, 2018 Author: Healthwise Staff Medical Review: William H. [myhealth.alberta.ca]

  Symptoms, which are often non-specific, begin 3 to 5 days after the bite with an abrupt onset of fever and any of these: headaches, chills, malaise, photophobia, myalgias, nausea, vomiting, diarrhea and abdominal pain. [lymediseaseassociation.org]

  Other uncommon clinical presentations include photophobia, diarrhea, hepatitis, epididymo-orchitis, arthritis, hemorrhagic diathesis, carditis, pneumonia, and even coma. [symptoma.com]

  Sudden fever Excessive sweating Severe muscle aches Joint stiffness Headache Photophobia (sensitivity to light) Nausea and vomiting Generalized weakness Complement fixation to Colorado tick virus Immunofluorescence for Colorado tick fever -- will be positive [doctor-clinic.org]

  Other symptoms include: Feeling weak all over and muscle aches Headache behind the eyes Lethargy (sleepiness) or confusion Nausea and vomiting Rash (may be light colored) Sensitivity to light ( photophobia ) Skin pain Sweating The health care provider [nlm.nih.gov]

• Retroorbital Pain

  Stiff neck, retroorbital pain, photophobia [1], nausea and vomiting, abdominal pain, diarrhea, and sore throat all have been reported in a minority of patients. [emedicine.medscape.com]

• Headache

  Symptoms generally include acute onset of fever, headache, chills, and myalgias; illness often lasts for 3 weeks or more. [ncbi.nlm.nih.gov]

  The initial symptoms of the disease often include fever, chills, headache, muscular and skeletal pain, and malaise. Other symptoms may include nausea, vomiting, stomach pain, light sensitivity and sore throat. [aldf.com]

  Symptoms fever headache chills light sensitivity myalgias malaise fatigue and malaise, for weeks to months nausea, diarrhea light sensitivity rare pneumonitis myocarditis hepatitis Signs and tests Complement fixation antibody test Immunofluorescence antibody [whatislyme.com]

  Typical symptoms include fever, headache, abdominal pain, vomiting and muscle pain. A rash may develop after a few days. In some cases, a rash does not appear at all. [orkin.com]

• Lethargy

  LOCATION Mountains or highlands regions of western states and western Canada that contain rocky surfaces with moderate shrub cover and scattered pines CAUSE Acute and benign disease from getting bitten by a tick SYMPTOMS High fever Headache Muscle aches Lethargy [crittercontrolhamiltoncounty.com]

  Other symptoms include: Feeling weak all over and muscle aches Headache behind the eyes Lethargy (sleepiness) or confusion Nausea and vomiting Rash (may be light colored) Sensitivity to light ( photophobia ) Skin pain Sweating The health care provider [nlm.nih.gov]

  Other symptoms include: Feeling weak all over and muscle aches Headache behind the eyes Lethargy (sleepiness) or confusion Nausea and vomiting Rash (may be light-colored) Sensitivity to light ( photophobia ) Skin pain Sweating Exams and Tests The health [ufhealth.org]

• Neck Stiffness

  Cerebrospinal fluid analysis may be warranted in CTF patients presenting with neck stiffness or features of encephalitis and may reveal mild protein elevation with lymphocytic pleocytosis. [symptoma.com]

  CNS illnesses are commonly characterized by severe headache, sensory impairment, neck stiffness and light sensitivity. Diagnosis An initial diagnosis is based on the patient’s signs and symptoms and confirmation depends on laboratory testing. [aldf.com]

Initial clinical diagnosis of CTF is based on the patient's history of travel to endemic areas with probable tick bites followed by fever and fatigue. Physical examination findings are not specific although a maculopapular rash and nuchal rigidity may be present. Routine laboratory tests like complete blood count, erythrocyte sedimentation rate, and liver function tests are ordered. Atypical lymphocytes [7], relative lymphocytosis, thrombocytopenia, and leukopenia are often noticed in CTF patients. Certain patients may have elevated levels of liver transaminases. The diagnosis of CTF can be confirmed with the detection of viral RNA and specific immunoglobulins in serum. Reverse-transcriptase polymerase chain reaction (RT-PCR) is a more useful test in early phases of the disease since serological tests may not be positive until 2-3 weeks after the patient's initial clinical presentation. Cerebrospinal fluid analysis may be warranted in CTF patients presenting with neck stiffness or features of encephalitis and may reveal mild protein elevation with lymphocytic pleocytosis. Finally, genetic material can be isolated from the tick to confirm the presence of a virus [10].

Radiological investigations are not helpful in the diagnosis or management of CTF except in cases of central nervous system involvement. Magnetic resonance imaging can be considered in cases presenting with features of encephalitis or other serious neurological diseases.

• Leukopenia

  Colorado tick fever should be clinically suspected in patients presenting with a biphasic febrile illness and leukopenia following tick exposure in the appropriate geographic area. [ncbi.nlm.nih.gov]

  Atypical lymphocytes, relative lymphocytosis, thrombocytopenia, and leukopenia are often noticed in CTF patients. Certain patients may have elevated levels of liver transaminases. [symptoma.com]

  […] sensitivity to light) Nausea and vomiting Generalized weakness Complement fixation to Colorado tick virus Immunofluorescence for Colorado tick fever -- will be positive if the person has the disease Diagnostic tests A complete blood count demonstrating leukopenia [doctor-clinic.org]

  Leukopenia, a decrease in the number of circulating white blood cells, is the most common laboratory finding in CTF. [aldf.com]

If complications develop, treatment will be aimed at controlling the symptoms. Colorado tick fever usually goes away by itself and is not dangerous. [nlm.nih.gov]

Other blood tests may include: Complete blood count ( CBC ) Liver function tests Treatment There are no specific treatments for this viral infection. The provider will make sure the tick is fully removed from the skin. [ufhealth.org]

What is the treatment for CTF? There is no specific treatment for CTF. Symptomatic relief includes treatment of fever and pain with acetominophen and analgesics. [web.archive.org]

Prognosis The prognosis for patients with Colorado tick fever is excellent, even in cases complicated by neurologic symptoms. Although prompt recovery is the expected outcome, rare fatalities have been reported. [emedicine.com]

The reverse transcriptase PCR method is a promising tool for the early diagnosis of CTF viral infection, or for ruling out CTF virus as the etiologic agent, in order to facilitate appropriate medical support. [ncbi.nlm.nih.gov]

The Epstein-Barr virus has been implicated as an etiological agent in some cases of Hodgkin's lymphoma. Herpes simplex infections are one of the few viral infections that can be controlled with chemotherapeutic agents. [quizlet.com]

Pathophysiology and Etiology The cause of Colorado tick fever is infection with the causative agent that is transmitted by a tick bite. This agent is a double-stranded RNA virus of the genus Coltivirus in the family Reoviridae. [emedicine.com]

Additional descriptive epidemiologic data were obtained by medical record abstraction. Ninety-one cases were identified from 1995 to 2003, resulting in an overall annual incidence of 2.7 per 1,000,000 population. [ncbi.nlm.nih.gov]

Colorado tick fever: clinical, epidemiologic, and laboratory aspects of 228 cases in Colorado in 1973-1974. Ann Intern Med. 1978 Mar. 88(3):303-10. [Medline]. Crowder CD, Rounds MA, Phillipson CA, et al. [emedicine.com]

Pathophysiology and Etiology The cause of Colorado tick fever is infection with the causative agent that is transmitted by a tick bite. This agent is a double-stranded RNA virus of the genus Coltivirus in the family Reoviridae. [emedicine.com]

Heightened awareness for the disease and tick prevention messages should be part of public health measures to further decrease the incidence of disease. [ncbi.nlm.nih.gov]

Prevention of tick-borne diseases. Med Clin North Am. 2002 Mar. 86(2):219-38. [Medline]. Centers for Disease Control and Prevention. Colorado Tick Fever: Prevention. Available at http://www.cdc.gov/coloradotickfever/prevention.html. [emedicine.com]

1. Spruance SL, Bailey A. Colorado tick fever: a review of 115 laboratory confirmed cases. Arch Intern Med. 1973;131:288-293
2. Goodpasture HC, Poland JD, Francy DB, et al. Colorado tick fever: clinical, epidemiologic, and laboratory aspects of 228 cases in Colorado in 1973-1974. Ann Intern Med.1978;88(3):303-310.
3. Fraser CH, Schiff DW. Colorado tick fever encephalitis: report of a case. Pediatrics. 1962;29:187-190
4. Florio L, Miller MS, Mugrage ER. Colorado tick fever: recovery of virus from human cerebrospinal fluid. J. infect Dis. 1952; 91:285-289
5. Silver HK, Meiklejohn G, Kempe CH. Colorado tick fever. An J Dis Child. 1961;101: 30-36
6. Romero JR, Simonsen KA. Powassan encephalitis and colorado tick fever. Infect Dis Clin North Am. 2008;22(3):545-559,
7. Meagher KE, Decker CF. Other tick-borne illnesses: tularemia, Colorado tick fever, tick paralysis. Dis Mon. 2012;58 (6):370-376.
8. Hierholzer WJ, Barry DW. Colorado tick fever pericarditis. JAMA. 1971;217:825
9. Emmons RW, Schade HI. Colorado tick fever simulating acute myocardial infarction. JAMA.1972;222:87-88
10. Crowder CD, Rounds MA, Phillipson CA, et al. Extraction of total nucleic acids from ticks for the detection of bacterial and viral pathogens. J Med Entomol. 2010;47(1):89-94.