Submitted to: Proceedings of the Entomological Society of Washington
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2005
Publication Date: 10/3/2005
Citation: Carroll, J.F., Cyr, T.L. 2005. A note on the densities of ixodes scapularis (acari: ixodidae) and white-tailed deer on the campus of the National Institute of Standards and Technology, Maryland USA. Entomological Society of America Proceedings. 107:973-976. Interpretive Summary: In many parts of the U.S., the blacklegged tick, Ixodes scapularis, is the principal vector of the pathogen causing Lyme disease. In locations where ticks are plentiful there are generally many white-tailed deer, the primary host for adult I. scapularis. The campus of the National Institute of Standards and Technology (NIST) is located in a county in Maryland where I. scapularis is common. The fenced NIST campus has been so densely populated with deer that an experimental contraceptive program was initiated in the 1990s. Only recently, however, have NIST employees complained about ticks. We conducted a tick survey at NIST in 2003 and 2004, and found an unusually low density of I. scapularis. Furthermore, the few adult I. scapularis we captured had a high infection rate for the Lyme disease pathogen, whereas all the nymphs captured tested negative. Habitat degradation caused by an over abundance of deer appears to have created conditions unfavorable for many species normally fed upon by larval and nymphal I. scapularis. Thus, there were few I. scapularis nymphs and adults in spite of a high density of deer. These findings are of interest to ecologists and epidemiologists because the NIST situation represents an extreme perturbation of the host-parasite-pathogen equilibriums typical of less disturbed and fragmented ecosystems.
Technical Abstract: Mesic woodlots at the campus of the National Institute of Standards and Technology (NIST), Gaithersburg, MD were surveyed for ticks by flagging in 2003 and 2004. Although the campus is in a county whre the blacklegged tick, Ixodes scapularis, principal vector of the agent causing Lyme disease, is common in suitable habitats, few nymphs and adults were captured. Densities of white-tailed deer, Odocoileus virginianus, primary host of adult I. scapularis, at the fenced NIST campus were high, ranging from 80-120 deer/km sq over the past 10 yr. Unlike nymphs and adults that were found at about only hald the sampling sites, I. scapularis larvae were present in moderate numbers at all sampling sites. In PCR tests, all adult I. scapularis captured were positive for Borrelia burdgorferi,causative agent of Lyme disease, whereas none of the nymphs captured were positive. Sever degradation of fragmented habitat by an excessively dense population of deer may have made the NIST campus unsuitable for many and nymphal host species normally occurring in Maryland woodlots and unfavorable for survival of free-living I. scapularis. The low tick densities and unusual infection rates at NIST may be a manifestation the ostensibly depauperate host community.