Treatment:

 PO – for rash, cranial nerve palsy, carditis, or arthritis
  • Doxycycline 100mg PO BID x 14 days
  • Amoxicillin  500mg PO TID x 14 days (use if pregnant)
  • Cefuroxime 500mg PO BID x 14 days
IV – for meningitis
  • Ceftriaxone 2gm qD x 14 days
  • Cefotaxime 2gm TID x 14 days

Cause:

  • Borrelia burgdorferi spirochete in the USA
  • Borrelia afzelli, Borelia garinii, Borellia burgdorferi spirochetes in Europe and Asia

Rash:

  • Most common symptoms
  • Erythema migrans
  • Begins as small papules and macules at site of tick bite 1-2 weeks after infection.
  • Other lesions may spring up elsewhere due to hemotogenous spread, and are typically smaller.
  • As lesions grow, central vesicles, necrotic areas, or clearing may occur. 75% do not have central clearing.
  • Asymptomatic, pruritic, or painful (lest likely)
  • Can grow as large as 2ft diameter and last 3-4 weeks.

Other symptoms:

  • fatigue
  • headache
  • arthralgia (most commonly knee)
  • myalgia
  • fever (less common)
  • facial nerve palsy
  • meningitis (mimics aseptic meningitis)
  • myocarditis, heart block

Testing:

Serologic testing (IgM & IgG antibodies) is inaccurate and can be negative in early disease. In addition, IgM levels can persist beyond acute infection even with treatment. Testing is not recommended. Antibiotic treatment is recommended based on clinical symptoms.

Incidence:

Highest age 5-14  and 40-50.

Geography:

  • New England
  • Mid-Atlantic
  • Northern Midwestern (Wisconsin and Minnesota)
  • Pacific coastal region (Oregon and Northern California)

Transmission: 

  • Natural hosts are mice, chipmunks, small mammals and birds.
  • Vector ticks bite the hosts, are carried on deer, and bite humans. (Ixodes scapularis and Ixodes pacificus)
  • Spring and summer bring high activity and correspond with the nymphal stage of the tick lifecycle.
  • No studies have ever shown evidence for congenital transmission of Lyme disease.

Source:

Shapiro ED. Clinical practice. Lyme disease. N Engl J Med. 2014;370(18):1724-31. PubMed
(ABEM LLSA 2017)

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