The Use of Deer Vehicle Accidents as a Proxy for Measuring the Degree of Interaction between Human and Deer Populations and Its Correlation with the Incidence Rate of Lyme Disease

Article excerpt

Introduction

The transmission of Lyme disease is well documented. The spirochete that causes Lyme disease, Borrelia burgdorferi, is transmitted by ticks of the genus Ixodes (Burgdorfer et al., 1982; Spielman, Wilson, Levine, & Piesman, 1985; Steere, Broderick, & Malawista, 1978) specifically Ixodes scapularis in the north central and northeastern U.S., and Ixodes pacificus in the western U.S. (Oliver et al., 1993). In the northeast, white-footed mice (Peromys cus leucopus), the major reservoir for B. burgdorferi, are the host to immature I. scapularis, while white-tailed deer (Odocoileus virginianus) are the primary host to adult I. scapularis (Bosler, Ormiston, Coleman, Hanrahan, & Benach, 1984; Spielman et al., 1985). White-tailed deer are an incompetent reservoir for B. burgdorferi, but serve as the primary blood meal for most adult female I. scapularis in the northeast (Rand et al., 2003; Wilson, Telford, Piesman, & Spielman, 1988).

The incidence and geographical distribution of Lyme disease in humans has been correlated with the distribution, abundance, and annual fluctuations in I. scapularis populations infected with B. burgdorferi (Mather, Nicholson, Donnelly, & Matyas, 1996; Stafford, Cartter, Magnarelli, Ertel, & Mshar, 1998). The nymphal I. scapularis become active during the summer months, and Lyme disease symptoms are seen approximately 7-21 days later in humans following a tick bite (Bacon, Kugeler, Mead, & Centers for Disease Control and Prevention [CDC], 2008). Lyme disease features a common clinical characteristic, a target lesion called erythema chronicum migrans and manifests symptoms of arthritis, myocarditis, uveitis, and meningoneuritis (Steere, 1986, 1994; Steere et al., 1977). The abundance of I. scapularis has been correlated with the number of deer in a geographic region (Wilson, Adler, & Spielman, 1985). As the deer population is a proxy for the presence of tick vectors, the presence of deer among humans has been hypothesized to be a risk of Lyme disease infection (Steere, Taylor, Wilson, Levine, & Spielman, 1986).

Much of New England has the four critical components necessary for human infection of B. burgdorferi: a population of I. scapularis, a population of white-tailed deer, a prevalence of B. burgdorferi in white-footed mice, and a human population that lives in proximity with deer. In areas in which Lyme disease is prevalent, specifically in forested residential areas, exposure to I. scapularis often occurs in the vicinity of people's homes (Lastavica, Wilson, Berardi, Spielman, & Deblinger, 1989; Steere, 1986). The number of deer living near these homes should influence the number of adult I. scapularis and the incidence of Lyme disease in the human population (Lastavica et al., 1989).

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An accurate method for quantifying the interaction between humans and deer in a geographic area has been lacking. Interaction between humans and deer simply means the co-residence of deer and humans and the inevitable resulting indirect contact, such as exposure to the same or bordering habitats. Currently, the main methods of documenting human and deer interaction are through hunter and residential deer surveys (Rand et al., 2003; Rand, Lacombe, Smith, Gensheimer, & Dennis, 1996; Wilson, Levine, & Spielman, 1984). Human-to-deer interaction surveys are the only measure that correlates with the incidence of Lyme disease in humans; all other measures found to correlate with Lyme disease are specific to Ixodes spp., and therefore only serve to explain the relationship of Lyme disease within a habitat and do not correspond to the human population. A useful correlative measure of Lyme disease incidence would be significant as it would have many public health implications in relation to the control of Lyme disease. Public health departments could direct Lyme prevention resources toward specific geographic areas based on the degree of correlation of the measure. …