Prevalence of Ixodes dammini near the homes of Lyme disease patients in Westchester County, New York.

Cases of Lyme disease that occurred in Westchester County, an affluent suburb north of New York City, in 1983 were investigated in 1983 and 1984 to determine the presence of Ixodes dammini (Acari: Ixodidae) in the vicinity of the patients' homes. Small mammal trapping, drag cloth, and carbon dioxide-baited tick traps were used to sample ticks. In all but one of 11 cases investigated, I. dammini was found on or near well-maintained lawns in the immediate vicinity of the residences. A mark-release-recapture experiment to determine tick abundance in one 700 m2 lawn resulted in an estimate of 6800 adult ticks (approximately 1 per m2). Dark-field microscopic examination of tick midgut tissues revealed that 33% of nymphs and 55% of adult ticks from this lawn contained spirochetes. These data suggest that many cases of Lyme disease in Westchester County, New York, may be acquired at home as a result of activities on the lawn.