Lyme Disease: Diagnosis and Treatment
Prophylaxis After Tick Bite
For high-risk tick bites, administer a single dose of doxycycline 200 mg (adults) or 4.4 mg/kg up to 200 mg (children ≥8 years) within 72 hours of tick removal. 1
Criteria for Prophylactic Doxycycline (ALL must be met):
- Identified Ixodes scapularis tick (reliable species identification) 1
- Tick attached ≥36 hours (based on engorgement or known exposure time) 1
- Prophylaxis started within 72 hours of tick removal 1
- Endemic area with ≥20% tick infection rate (parts of New England, mid-Atlantic, Minnesota, Wisconsin) 1
- No contraindications to doxycycline 1
Key Points on Prophylaxis:
- Do NOT use prophylaxis for equivocal or low-risk bites—use wait-and-watch approach instead 1
- Do NOT test asymptomatic patients for Borrelia exposure after tick bite 1
- Do NOT substitute amoxicillin for doxycycline prophylaxis in contraindicated patients—observation is preferred given low risk of serious complications 1
- Submit tick for species identification to confirm Ixodes species 1
Diagnosis of Early Localized Disease (Erythema Migrans)
Diagnose erythema migrans clinically without laboratory testing in patients with compatible skin lesions and tick exposure in endemic areas. 1
Diagnostic Approach:
- Clinical diagnosis alone is sufficient for typical erythema migrans lesions 1
- Laboratory testing NOT recommended for typical presentations—serology is often negative early in disease 1
- Consider antibody testing only for atypical lesions (acute-phase serum, followed by convalescent-phase 2-3 weeks later if negative) 1
- Do NOT delay treatment while awaiting laboratory confirmation 2
Treatment of Early Localized Disease (Erythema Migrans)
Treat adults with doxycycline 100 mg orally twice daily for 10 days as first-line therapy. 1, 2, 3
First-Line Oral Regimens for Adults:
- Doxycycline 100 mg twice daily for 10 days (preferred—shorter duration, covers HGA co-infection) 1, 2, 3
- Amoxicillin 500 mg three times daily for 14 days (alternative first-line) 1, 2, 3
- Cefuroxime axetil 500 mg twice daily for 14 days (alternative first-line) 1, 2, 3
Doxycycline Administration:
- Take with 8 ounces of fluid to reduce esophageal irritation 2, 4
- Can be taken with food to reduce GI intolerance 2, 4
- Advise sun avoidance due to photosensitivity risk 2, 4
Treatment for Children Under 8 Years
For children <8 years, use amoxicillin 50 mg/kg/day in 3 divided doses (maximum 500 mg per dose) for 14 days as first-line therapy. 4, 3
Pediatric First-Line Options:
- Amoxicillin 50 mg/kg/day in 3 divided doses (max 500 mg/dose) for 14 days 4, 3
- Cefuroxime axetil 30 mg/kg/day in 2 divided doses (max 500 mg/dose) for 14 days 4, 3
Evolving Evidence on Doxycycline in Young Children:
- Doxycycline is increasingly used in children <8 years for Lyme disease 5, 6
- Short courses (≤3 weeks) appear safe with minimal tooth staining risk 5, 6
- Amoxicillin remains preferred for non-neurological disease in young children, but doxycycline is a safe alternative when needed 5
Treatment for Pregnant or Lactating Women
Treat pregnant and lactating women identically to non-pregnant patients, but avoid doxycycline—use amoxicillin or cefuroxime axetil instead. 1, 3
Regimens for Pregnancy/Lactation:
- Amoxicillin 500 mg three times daily for 14 days 1, 3
- Cefuroxime axetil 500 mg twice daily for 14 days 1, 3
- Doxycycline is relatively contraindicated in pregnancy and lactation 1, 2
Treatment of Disseminated Neurologic Disease
For Lyme meningitis or radiculopathy, use parenteral ceftriaxone 2 g IV daily for 14 days (range 10-28 days). 1
Neurologic Manifestations:
- Meningitis or radiculopathy: Parenteral regimen (ceftriaxone or penicillin G) for 14 days (10-28 days) 1
- Cranial nerve palsy alone: Oral regimen (doxycycline, amoxicillin, or cefuroxime) for 14 days (14-21 days) 1
- Oral doxycycline 200-400 mg/day in 2 divided doses for 10-28 days is an acceptable alternative to IV therapy for neurologic disease 2
Critical Pitfall:
- Screen for subtle neurologic symptoms (distal paresthesias, memory impairment) before initiating oral therapy—these patients may develop neuroborreliosis and require IV ceftriaxone 3
Treatment of Cardiac Involvement
For Lyme carditis, use oral or parenteral regimens for 14 days (14-21 days) depending on severity. 1
Cardiac Disease Approach:
- Oral regimen acceptable for mild cardiac involvement 1
- Parenteral regimen recommended for advanced atrioventricular heart block 1
- Duration: 14 days (range 14-21 days) 1
Second-Line Agents (Use Only When First-Line Contraindicated)
Macrolides (azithromycin, clarithromycin, erythromycin) are less effective than doxycycline and should only be used when first-line agents are not tolerated. 2, 3
Macrolide Regimens:
- Azithromycin 500 mg daily for 7-10 days (7 days preferred in US) 1, 3
- Clarithromycin 500 mg twice daily for 14-21 days 3
- Erythromycin 500 mg four times daily for 14-21 days 3
Critical Pitfalls to Avoid
Ineffective Antibiotics (NEVER USE):
- First-generation cephalosporins (cephalexin) are completely ineffective against B. burgdorferi 2, 4, 3
- Fluoroquinolones, carbapenems, vancomycin, metronidazole, trimethoprim-sulfamethoxazole are not recommended 1
- Benzathine penicillin G is ineffective 1
Treatment Duration Errors:
- Do NOT extend treatment beyond 21 days for early Lyme disease—no evidence of benefit 2
- Do NOT use pulsed-dosing or long-term antibiotic therapy 1
Co-infection Considerations
Consider co-infection with Anaplasma phagocytophilum (HGA) or Babesia microti in patients with severe symptoms, high fever >48 hours despite treatment, or unexplained cytopenias. 1, 3
When to Suspect Co-infection:
- High-grade fever persisting >48 hours despite appropriate Lyme treatment 1, 3
- Unexplained leukopenia, thrombocytopenia, or anemia 1, 3
- More severe initial symptoms than typical for Lyme disease alone 1
- Resolved erythema migrans but worsening viral-like symptoms 1