Tick-Borne Diseases

Tick-Borne Diseases

 

Tick-borne diseases in the United States include Lyme disease, human ehrlichiosis (human monocytic ehrlichiosis [HME] and human granulocytic anaplasmosis [HGA]), Rocky Mountain spotted fever, babesiosis and Colorado tick fever.  (See separate topics for Borrelia burgdorferi [Lyme disease], Babesia microti [Babesiosis] and Rickettsia rickettsii [Rocky Mountain Spotted Fever].)

Ehrlichiosis

  • Epidemiology
    • Transmission
      • HGA – tick: Ixodes scapular; species: white-footed mouse and white-tailed deer
      • HME – tick: Amblyomma americanum and Dermatocentor variabilis; species: white-tailed deer
  • Organism
    • HGA – Anaplasma phagocytophilum
    • HME – Ehrlichia chaffeensis
  • Risk Factors
    • Exposure in regions where tick is endemic
      • HGA – upper Midwest and northeast U.S.; May through August
      • HME – south central and southeast U.S.; May through August
  • Clinical Presentation
    • Influenza-like – headache, myalgias, fever, chills, malaise, cough
    • Rash – macular, maculopapular or petechial
      • Rare in HGA
  • Diagnosis
    • Wright stained smear – presence of morulae
    • Culture
    • Seroconversion by IFA
  • Treatment
    • Antibiotics

Colorado Tick Fever

  • Epidemiology
    • Incidence – Rocky Mountains
    • Transmission – tick: Dermatocentor andersoni; species: small rodents
  • Organism
    • Double-stranded DNA arbovirus
  • Clinical Presentation
    • Identical to Ehrlichiosis, no rash
  • Diagnosis
    • Blood smears (stained with immunofluorescence)
  • Treatment
    • Supportive

See Also