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Tick-Borne Diseases, Colorado: Differential Diagnoses & Workup

Author: Jonathan A Edlow, MD, Associate Professor of Medicine, Department of Emergency Medicine, Harvard Medical School; Vice Chairman, Department of Emergency Medicine, Beth Israel Deaconess Medical Center
Contributor Information and Disclosures

Updated: Dec 9, 2008

Differential Diagnoses

CBRNE - Q Fever
Tick-Borne Diseases, Q Fever
Tick-Borne Diseases, Ehrlichiosis
Tick-Borne Diseases, Relapsing Fever
Tick-Borne Diseases, Introduction
Tick-Borne Diseases, Rocky Mountain Spotted Fever
Tick-Borne Diseases, Lyme
Tick-Borne Diseases, Tularemia

Workup

Laboratory Studies

  • Laboratory studies are not helpful.
  • The WBC count is mildly depressed (mean, about 3900 per mm3) in about 66% of patients. Leukopenia may suggest the diagnosis. Rarely, thrombocytopenia occurs.
  • Occasionally, patients with Colorado tick fever have elevated hepatic transaminase levels (in the mid-hundreds range).
  • CSF analysis may show mild-to-moderate lymphocytic pleocytosis (up to 300 cells/mm3) and mildly elevated protein levels.

Other Tests

  • Because the clinical features of Colorado tick fever are nonspecific, establish the diagnosis in the proper epidemiologic context. Confirmation is based on serologic test results or virus inoculation in mice. In addition, newer reverse transcriptase polymerase chain reaction (PCR) techniques exist and may be helpful in diagnosing the disease in the first 5 days of illness.
    • Neutralizing antibodies appear in about one third of cases by day 10 and in nearly all patients by 1 month after infection.
    • A 4-fold increase in titers between specimens drawn during the acute phase and those from convalescence is observed in nearly all patients.
    • The assay, with complement fixation or immunofluorescent techniques, must be performed in a laboratory with experience in performing this test.
    • Antibodies to the Colorado tick virus frequently are found in perennial campers who frequent endemic areas; thus, single elevated titers of immunoglobulin G do not necessarily indicate acute infection. This finding also suggests asymptomatic seroconversion.
  • Although viral testing is not routinely available, the virus can be detected in the blood for 2-4 weeks after infection.

More on Tick-Borne Diseases, Colorado

Overview: Tick-Borne Diseases, Colorado
Differential Diagnoses & Workup: Tick-Borne Diseases, Colorado
Treatment & Medication: Tick-Borne Diseases, Colorado
Follow-up: Tick-Borne Diseases, Colorado
Multimedia: Tick-Borne Diseases, Colorado
References
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References

  1. Emmons RW. Ecology of Colorado tick fever. Annu Rev Microbiol. 1988;42:49-64. [Medline].

  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. Mar 1978;88(3):303-10. [Medline].

  3. Klasco R. Colorado tick fever. Med Clin North Am. Mar 2002;86(2):435-40, ix. [Medline].

  4. Leiby DA, Gill JE. Transfusion-transmitted tick-borne infections: a cornucopia of threats. Transfus Med Rev. Oct 2004;18(4):293-306. [Medline].

  5. Romero JR, Simonsen KA. Powassan encephalitis and colorado tick fever. Infect Dis Clin North Am. Sep 2008;22(3):545-59, x. [Medline].

  6. Spruance SL, Bailey A. Colorado Tick Fever. A review of 115 laboratory confirmed cases. Arch Intern Med. Feb 1973;131(2):288-93. [Medline].

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Further Reading

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Keywords

tick-borne diseases, Colorado tick fever, tick bite,  Dermacentor andersoni, D andersoni, Orbivirus, vector-borne disease, wood tick, Coltivirus, RNA virus, tick-borne viral diseases, tick-borne virus, Rocky Mountain spotted fever, tick bite, viral infection

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Contributor Information and Disclosures

Author

Jonathan A Edlow, MD, Associate Professor of Medicine, Department of Emergency Medicine, Harvard Medical School; Vice Chairman, Department of Emergency Medicine, Beth Israel Deaconess Medical Center
Jonathan A Edlow, MD is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Medical Editor

Dan Danzl, MD, Chair, Department of Emergency Medicine, Professor, University of Louisville Hospital
Dan Danzl, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, Kentucky Medical Association, Society for Academic Emergency Medicine, and Wilderness Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Jon Mark Hirshon, MD, MPH, Associate Professor, Department of Emergency Medicine, University of Maryland School of Medicine
Jon Mark Hirshon, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Public Health Association, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center
John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Chief Editor

Rick Kulkarni, MD, Medical Director, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: WebMD Salary Employment

 
 
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