Medical Dictionary

Lyme disease

1. A subacute inflammatory disorder caused by infection with Borrelia burgdorferi, a nonpyogenic spirochete transmitted by Ixodes scapularis, the deer tick, in the eastern U.S. and I. pacificus, the western black-legged tick, in the western U.S. The characteristic skin lesion, erythema chronicum migrans, is usually preceded or accompanied by fever, malaise, fatigue, headache, and stiff neck. Neurologic, cardiac, or articular manifestations may occur weeks to months later. Tick nymphs are thought to be responsible for about 90% of transmission to human beings. Nymphs and larvae feed especially on the white-footed mouse, Peromyscus leucopus, while the preferred host of adults is the white-tailed deer, Odocoileus virginianus. Infected reservoir animals and ticks do not become ill. Residual articular or neurologic symptoms, which may persist for months or years after the initial infection, presumably reflect an immune response to the organism. Variations in clinical features or severity from one patient to another may be due to inborn variations in immune response, perhaps linked to the human lymphocytic antigen (HLA) system.

Syn: Lyme borreliosis

[Lyme, CT, where first observed]