Question
Lyme disease
Answer
Lyme disease is a tick-borne zoonotic infection caused by the spirochete Borrelia burgdorferi (and related genospecies), transmitted by infected Ixodes ticks, which acquire the organism from a reservoir of small mammals and deer.
Clinical stages:
- Early localized: pathognomonic erythema migrans — an expanding, annular, erythematous “bull’s-eye” rash at the tick-bite site, appearing days to weeks after the bite, often with fever, malaise, and lymphadenopathy.
- Early disseminated (weeks to months): multiple secondary erythema migrans lesions, neurological involvement (facial nerve palsy, lymphocytic meningitis), and cardiac involvement (AV conduction block, myocarditis).
- Late stage (months to years): Lyme arthritis — recurrent/chronic large-joint mono/oligoarthritis; chronic neurological manifestations in a minority of untreated patients.
Laboratory diagnosis: primarily clinical in the erythema migrans stage; serology (two-tier testing — screening ELISA followed by confirmatory Western blot) for later/disseminated stages; PCR on synovial fluid/CSF in selected cases.
Treatment: doxycycline (or amoxicillin/cefuroxime in children and pregnant women) for early disease; IV ceftriaxone for neuroborreliosis or Lyme carditis.
Prevention: avoiding tick-infested areas, protective clothing, tick repellents, and prompt removal of attached ticks.