Lyme Disease

GENERAL PRINCIPLES

Lyme borreliosis is a systemic illness of variable severity caused by the spirochete Borrelia burgdorferi and is the most common vector-borne disease in the US.

• Prophylactic doxycycline 200 mg PO (single dose) is recommended within 72 hours of removal of a high-risk tick bite meeting the following criteria: (1) an Ixodes spp. tick was identified, (2) the bite occurred in a highly endemic region, and (3) the tick was attached for ≥36 hours.⁴²

DIAGNOSIS

Clinical Presentation

Lyme disease has three distinct clinical stages, following an incubation period of 7-10 days:

• Stage 1 (early local disease) is characterized by mild constitutional symptoms and erythema migrans, a slowly expanding macular rash >5 cm in diameter, classically with central clearing (often not seen). This may be difficult to differentiate from Southern tick-associated rash illness, caused by the bite of the lone star tick (Amblyomma americanum), which presents with an erythema migrans-like lesion in the Midwest and Southern US.

• Stage 2 (early disseminated disease) occurs within several weeks to months and includes multiple erythema migrans lesions, neurologic symptoms (e.g., seventh cranial nerve palsy, meningoencephalitis), cardiac symptoms (atrioventricular block, myopericarditis), and asymmetric oligoarticular arthritis, most commonly affecting the knee.

• Stage 3 (late disease) occurs after months to years and includes chronic dermatitis, neurologic disease, and asymmetric monoarticular or oligoarticular arthritis. Chronic fatigue is not seen more frequently in patients with Lyme borreliosis than in control subjects.

Diagnostic Testing

Diagnosis rests on clinical suspicion in the appropriate setting but can be supported by two-tiered testing (e.g., enzyme immunoassay or indirect fluorescent antibody test followed by IgM and IgG immunoblots) with acute and convalescent serologies.

TREATMENT

• Treatment depends on stage and severity of disease. Oral therapy (doxycycline 100 mg PO q12h, amoxicillin 500 mg PO q8h, or cefuroxime axetil 500 mg PO q12h for 10-21 days) is used for early localized or disseminated disease without neurologic or cardiac involvement. The same agents, given for 28 days, are recommended for late Lyme disease. Doxycycline has the added benefit of covering potential coinfection with ehrlichiosis. In the setting of true β-lactam allergy and if doxycycline cannot be given, macrolides are an alternative with a lower cure rate (~80%).

• Parenteral therapy (e.g., ceftriaxone 2 g IV qday, cefotaxime 2 g IV q8h, penicillin G 3-4 million units IV q4h) for 14-21 days is preferred over oral therapy for severe neurologic or cardiac disease, regardless of the stage.⁴²