infectious diseases
Lyme Disease
Key Points
In the US, > 90% of Lyme disease cases occur from Maine to Virginia and in Wisconsin, Minnesota, and Michigan;Ixodes scapularis(the deer tick) is the primary vector in these areas. In the US, the white-footed mouse is the primary animal reservoir forBorrelia burgdorferiand the preferred host for nymphal and larval forms of the deer tick; deer are hosts for adult ticks but do not carryBorrelia. Lyme disease has 3 stages: early localized, early disseminated, and late. Erythema migrans is the first and best clinical indicator; it occurs in ≥ 75% of patients. In endemic areas, few patients who have arthralgias, fatigue, difficulty concentrating, or other nonspecific symptoms but who have had no history of erythema migrans or other symptoms of early-localized or early-disseminated Lyme disease actually have Lyme disease. Diagnose clinically if typical rash is present; otherwise, do acute and convalescent serologic testing (C6 ELISA confirmed by enzyme immunoassay or Western blot). Treat with oral or parenteral antibiotics depending on disease manifestations. 