Colorado tick fever

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  • Abbreviation: CTF
  • Also called mountain tick fever, American tick fever
  • Caused by RNA virus of genus Coltivirus in family Reoviridae
  • Principal vector is Rocky Mountain wood tick (Dermacentor andersoni)
  • Principal zoonotic reservoirs include deer, marmots, porcupines
  • Endemic in western mountainous regions of the U.S. and Canada (e.g. Colorado, Idaho)
  • Develops March to September, most cases occur in April, May, June [1]

Clinical features

  • Incubation time ranges from 1-14 days
  • Onset of illness characterized by fever (may be biphasic), chills, headache, myalgias, malaise, photophobia
  • Less commonly sore throat, vomiting, abdominal pain, skin rash (macular or petechial)
  • Rarely, patients may develop severe illness that affects central nervous system with symptoms including neck stiffness and confusion [2]

Differential diagnosis

Tick Borne Illnesses


  • Clinical diagnosis


  • Supportive care


See also


  1. Colorado tick fever. MedlinePlus. Retrieved 9/9/2017.
  2. Colorado tick fever. Center for Disease Control and Prevention. 13 Jan 2015. Retrieved 9/9/2017.