What are the initial treatment steps for a patient with a tick bite that may be infected with Lyme disease, prior to confirmation of the disease?

Initial Management of Suspected Lyme Disease Tick Bite

For a patient with a tick bite that might be bearing Lyme disease, prophylactic antibiotic therapy should only be given within 72 hours of tick removal if the bite meets all criteria for being high-risk; otherwise, a wait-and-watch approach is recommended. 1

Assessment of Tick Bite Risk

• A tick bite is considered high-risk only when it meets ALL three criteria:

  • The tick is identified as an Ixodes species vector (blacklegged tick)
  • The bite occurred in a highly endemic area for Lyme disease
  • The tick was attached for ≥36 hours (based on engorgement or known time of attachment) 1

• Testing the tick for B. burgdorferi is not recommended as it does not reliably predict the likelihood of clinical infection 1

• Diagnostic testing of asymptomatic patients following tick bites is not recommended 1

Management Algorithm

If High-Risk Bite (all criteria met) AND Within 72 Hours of Removal:

• Administer a single dose of oral doxycycline:

  • Adults: 200 mg single dose
  • Children ≥8 years: 4.4 mg/kg (maximum 200 mg) single dose 1

• Doxycycline is contraindicated in:

  • Pregnant women
  • Children <8 years of age 1

• Amoxicillin is NOT recommended as prophylaxis for those who cannot take doxycycline due to:

  • Lack of data on effective short-course regimens
  • Need for multi-day regimen (with associated adverse effects)
  • Excellent efficacy of treatment if infection develops
  • Low risk of serious complications from recognized tick bites 1

If Low-Risk Bite OR Beyond 72-Hour Window:

• Do NOT administer prophylactic antibiotics 1
• Prophylaxis after Ixodes pacificus bites (Western blacklegged tick) is generally not necessary due to low infection rates with B. burgdorferi in most endemic regions 1
• Animal studies show prophylaxis is ineffective when delivered ≥2 days after tick removal 2

Monitoring and Follow-up Instructions

• Monitor for symptoms for 30 days after the tick bite 3, 4:

  • Watch for erythema migrans (expanding red rash, sometimes with "bull's-eye" appearance) at the bite site
  • Monitor for flu-like symptoms (fever, headache, fatigue, muscle/joint pain)

• Seek immediate medical attention if:

  • An expanding skin lesion (erythema migrans) develops at the bite site
  • Flu-like symptoms develop within several weeks of the bite 3, 4

If Lyme Disease Develops (Erythema Migrans Present)

• For patients with erythema migrans, recommended treatments include:

  • Doxycycline: 10-day course (adults and children ≥8 years)
  • Amoxicillin: 14-day course (preferred for pregnant women and children <8 years)
  • Cefuroxime axetil: 14-day course (alternative option) 1

• Macrolide antibiotics (e.g., azithromycin) are not recommended as first-line therapy as they are less effective, but may be used if patients cannot tolerate the preferred options 1

Prevention of Future Tick Bites

• Use EPA-registered repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus, or 2-undecanone on exposed skin 3, 4
• Apply permethrin to clothing for additional protection 3
• Wear protective clothing (long-sleeved shirts, pants, closed-toe shoes) 4
• Perform regular tick checks after outdoor activities 4, 5

Important Caveats

• The 72-hour time limit for prophylaxis is based on lack of data on efficacy beyond this window 1
• The 20% infection rate threshold for prophylaxis generally occurs in parts of New England, mid-Atlantic states, Minnesota, and Wisconsin 1
• Previous Lyme disease vaccination or prior infection does not provide reliable long-term protection 1
• Doxycycline may cause photosensitivity; patients should avoid excessive sunlight exposure and use sunscreen 5