REDUCED ABUNDANCE OF IXODES-SCAPULARIS (ACARI, IXODIDAE) AND LYME-DISEASE RISK BY DEER EXCLUSION

The effect of deer exclosures upon the numbers of immature Ixodes scap ularis Say, the vector of Lyme disease in the eastern United States, w as examined at five sites in Westchester County, NY. Study areas range d in size from 6 to 101 ha where deer had been excluded for a period o f 25 yr by >2.4-m-high fencing that surrounded each site. A total area of 40,506 m(2) was drag-sampled during the study to measure tick abun dance. Nymphal densities (ticks per 1,000 m(2)) averaged 4.6 (range, 1 .3-9.6) inside exclosures and 27.7 (range, 7.3-79.4) outside. Larval d ensities averaged 36.7 (range, 1.2-132.1) inside exclosures and 354.4 (range, 7.5-914.5) outside. Comparisons between exclosure sites and ou tside areas immediately adjacent to the exclosure fence, where deer ha d unrestricted access, revealed that exclosures had 83% fewer host-see king nymphs and 90% fewer host-seeking larvae. Tick numbers inside exc losures did not always decline with increasing distance from the fence . There was no significant difference in the rate of Borrelia burgdorf eri Johnson, Schmid, Hyde, Steigerwalt & Brenner infection for host-se eking ticks collected inside (20%, n = 50) exclosures compared with ti cks collected outside (26%, n = 50) exclosures. Deer fencing may provi de a means of significantly reducing the abundance of I. scapularis an d the risk of Lyme disease in relatively large areas without the need to reduce or eliminate the deer population.