II. Pathophysiology

  1. Deer Tick (Ixodes Scapularis) Image derived from CDC
    1. IDVectorDeerTicks.jpg
  2. Deer Ticks have four stage life cycle over 2 years
    1. Egg
    2. Larva
    3. Nymph (most common form to transmit disease)
    4. Adult
  3. Transmission of disease
    1. Transmission unlikely before attached for 1-2 days
    2. Engorged nymph most likely to transmit disease

III. Pathophysiology: Diseases transmitted by the Deer Tick

IV. Differential Diagnosis

  1. American Dog Tick (Dermacentor variabilis)
    1. Twice the size of Deer Ticks
    2. Not associated with Lyme Disease
    3. Associated with Babesiosis

V. Management: Deer Tick Bite

  1. Prompt Tick Removal
    1. See Tick Removal
    2. Borrelia Burgdorferi infection transmission 1% at under 24 hours
    3. Borrelia Burgdorferi infection transmission 20% at over 72 hours
  2. Observe for Tick Borne Illness for 30 days after bite
    1. Erythema Migrans (Lyme Disease)
    2. If fever occurs, consider additional conditions
      1. Babesiosis
      2. HGA (previously known as Ehrlichiosis)
  3. Antibiotic Prophylaxis After Known Deer Tick Bite
    1. Routine prophylaxis is not recommended outside of Lyme Disease endemic areas
    2. Following known deer Tick Bite in endemic area
      1. Early Lyme DiseaseIncidence: 1.2%
    3. Antibiotics after deer Tick Bite in endemic area
      1. Doxycycline
        1. Dose within 72 hours of Tick Bite
          1. Adults: 200 mg orally for one dose
          2. Child >8 years: 4 mg/kg (max: 200 mg) orally for one dose
        2. Efficacy in preventing Lyme Disease: 87%
        3. References
          1. Nadelman (2001) N Engl J Med 345:133-4 [PubMed]
      2. No other antibiotic is indicated in prophylaxis
        1. Prior study showed some efficacy with Amoxicillin
          1. Shapiro (1992) N Engl J Med 327:1769 [PubMed]

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