- This is the most common vector-borne disease in the United States and is a systemic illness of variable severity caused by the spirochete Borrelia burgdorferi.
- It is seen in endemic regions, including northeastern coastal states, the upper Midwest, and northern California.
- It has three distinct stages, which start after an incubation period of 7-10 days:
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.
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.
- Diagnosis rests on clinical suspicion in the appropriate setting but can be supported by two-tiered serologic testing (screening enzyme-linked immunosorbent assay [ELISA] followed by Western blot).
- A substantial degree of coinfection occurs with babesiosis and ehrlichiosis.
Treatment depends on stage and severity of disease.
- Oral therapy (doxycycline, 100 mg PO bid; amoxicillin, 500 mg PO tid; or cefuroxime axetil, 500 mg PO bid 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.
- Parenteral therapy (ceftriaxone, 2 g IV daily; cefotaxime, 2 g IV q8h; 14-28penicillin G, 3-4 million units IV q4h) for 14-28 days should be used for severe neurologic or cardiac disease, regardless of stage.
- Prophylactic doxycycline, 200 mg PO single dose, may reduce the risk of Lyme disease in endemic areas following a bite by a nymph-stage deer tick.