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Doxycycline is recommended for persons with Ixodes scapularis tick bites in certain geographic areas, if the tick had fed for at least 36 hours. Based on the scutal index, over 40% of I. scapularis tick bites from patients seen at the Lyme Disease Diagnostic Center did not warrant antibiotic prophylaxis.

Genetic diversity of Anaplasma phagocytophilum was assessed in specimens from 16 infected patients and 16 infected Ixodes scapularis ticks. A region immediately downstream of the 16S rRNA gene, which included the gene encoding SdhC, was sequenced. For the A. phagocytophilum strains from patients no sequence differences were detected in this region. In contrast, significantly fewer ticks had a sequence encoding SdhC that was identical to that of the human strains (11/16 vs. 16/16, p = 0.04). This variation is consistent with the premise that not all A. phagocytophilum strains present in nature are able to cause clinical illness in humans. A strain referred to as A. phagocytophilumVariant-1 that is regarded as non-pathogenic for humans was previously described using a different typing method. Data from the current study suggest that both typing methods are identifying the same non-pathogenic strains.

Ticks expend energy while host-seeking and must consume blood to advance to the next life stage. The energy required for activity is derived from the tick's lipid reserves, a valuable resource that sustains the tick until it finds the next host and can take another bloodmeal. The amount of lipid reserves in an unfed tick has been proposed as an index of tick biological age. Two different methods for aging nymphal blacklegged ticks, Ixodes scapularis Say, were analyzed in this study. To study lipid usage, colony-raised nymphs were held in lab-controlled chambers at 21.0 °C and ≥95% relative humidity, with a photoperiod of 12:12 (L:D) h. Samples of ticks were frozen at -80 °C every 2-3 wk, starting at 12-wk postmolt and continuing until 38-wk postmolt. Lipid reserves were determined indirectly through measurements of "physiological age" that estimate the energy a tick has based on the evaluation of morphometric size ratios of the tick scutum and alloscutum, and quantified directly through chloroform extractions of lipid from individual ticks. Morphometric age ratios and lipid amounts were compared to determine if morphometric measurements accurately estimated a tick's physiological state. Although the morphometric age ratio did correlate significantly with total tick lipid content, the predictive value of the ratio was not reliable; chloroform extraction results showed that lipid amounts declined steadily through the study and more accurately characterized the physiological condition of nymphal I. scapularis. The study of physiological aging of blacklegged ticks may lead to a better understanding of how changing environmental conditions affect tick longevity.

Ixodes scapularis Say, the blacklegged tick, vectors Borrelia burgdorferi Johnson et al. 1984, the bacterium that causes Lyme disease, the most important vector-borne disease in the United States. Efforts to reduce I. scapularis populations are shifting toward the development of biological control methods. Currently, only a few entomopathogenic fungal species are considered virulent to ticks. We hypothesized that these species may not represent the most abundant local taxa that would be pathogenic to ticks in situ. To identify potential entomopathogenic fungi at a study site in Westchester County, New York, we sampled soils and ticks, extracted and amplified the internal transcribed spacer region of nuclear ribosomal DNA (nrDNA), and compared sequences with those in GenBank. Over three sampling periods from June 2007 to May 2008, 70 fungal taxa were isolated and identified from soils (48 taxa) and ticks (27 taxa; 5 taxa were found both in soil and on ticks) collected in this study, encompassing species in 25 different genera. In laboratory bioassays, 15 fungal taxa were found to be significantly virulent, although none of these were previously considered common pathogens of I. scapularis. Two species, Hypocrea lixii Patouillard 1891 and Penicillium soppii K. M. Zalessky 1927, were tested in field trials by spraying suspensions on forested plots. Mean tick mortality was 71% after treatment with H. lixii, 58% after treatment with P. soppii, and 32% in the control plots. The complete diversity of entomopathogenic fungal species at this site is yet to be defined, but, in general, such fungi appear to be more common in forest habitats where I. scapularis resides than previously thought. Examination of intact fungal communities can provide information that serves as the foundation for site-specific biocontrol programs.

As part of the Northeast Area-wide Tick Control Project (NEATCP), meta-analyses were performed using pooled data on the extent of tick-vector control achieved through seven concurrent studies, conducted within five states, using U.S. Department of Agriculture "4-Poster" devices to deliver targeted-acaricide to white-tailed deer. Although reductions in the abundance of all life-stages of Ixodes scapularis were the measured outcomes, this study focused on metrics associated with I. scapularis nymphal tick densities as this measure has consistently proven to directly correlate with human risk of acquiring Lyme disease. Since independent tick sampling schemes were undertaken at each of the five environmentally distinct study locations, a meta-analytic approach permitted estimation of a single true control-effect size for each treatment year of the NEATCP. The control-effect is expressed as the annual percent I. scapularis nymphal control most consistent with meta-analysis data for each treatment year. Our meta-analyses indicate that by the sixth treatment year, the NEATCP effectively reduced the relative density of I. scapularis nymphs by 71% on the 5.14 km(2) treatment sites, corresponding to a 71% lower relative entomologic risk index for acquiring Lyme disease.

Entomopathogenic fungi are commonly found in forested soils that provide tick habitat, and many species are pathogenic to Ixodes scapularis Say, the blacklegged tick. As a first step to developing effective biocontrol strategies, the objective of this study was to determine the best methods to isolate entomopathogenic fungal species from field-collected samples of soils and ticks from an Eastern deciduous forest where I. scapularis is common. Several methods were assessed: (1) soils, leaf litter, and ticks were plated on two types of media; (2) soils were assayed for entomopathogenic fungi using the Galleria bait method; (3) DNA from internal transcribed spacer (ITS) regions of the nuclear ribosomal repeat was extracted from pure cultures obtained from soils, Galleria, and ticks and was amplified and sequenced; and (4) DNA was extracted directly from ticks, amplified, and sequenced. We conclude that (1) ticks encounter potentially entomopathogenic fungi more often in soil than in leaf litter, (2) many species of potentially entomopathogenic fungi found in the soil can readily be cultured, (3) the Galleria bait method is a sufficiently efficient method for isolation of these fungi from soils, and (4) although DNA extraction from ticks was not possible in this study because of small sample size, DNA extraction from fungi isolated from soils and from ticks was successful and provided clean sequences in 100 and 73% of samples, respectively. A combination of the above methods is clearly necessary for optimal characterization of entomopathogenic fungi associated with ticks in the environment.

Blacklegged ticks (Ixodes scapularis) are one of the most important pathogen vectors in the United States, responsible for transmitting Lyme disease and other tick-borne diseases. The structure of a host's microbial community has the potential to affect the ecology and evolution of the host. We employed high-throughput sequencing of the 16S rRNA gene V3-V4 hypervariable regions in the first study to investigate the tick microbiome across all developmental stages (larvae, nymphs, adults). In addition to field-collected life stages, newly hatched lab-reared larvae were studied to determine the baseline microbial community structure and to assess transovarial transmission. We also targeted midguts and salivary glands due to their importance in pathogen maintenance and transmission. Over 100,000 sequences were produced per life stage replicate. Rickettsia was the most abundant bacterial genus across all sample types matching mostly the Ixodes rickettsial endosymbionts, and its proportion decreased as developmental stage progressed, with the exception of adult females that harbored a mean relative abundance of 97.9%. Lab-reared larvae displayed the lowest bacterial diversity, containing almost exclusively Rickettsia. Many of the remaining bacteria included genera associated with soil, water, and plants, suggesting environmental acquisition while off-host. Female organs exhibited significantly different β-diversity than the whole tick from which they were derived. Our results demonstrate clear differences in both α and β diversity among tick developmental stages and between tick organs and the tick as a whole. Furthermore, field-acquired bacteria appear to be very important to the overall internal bacterial community of this tick species, with influence from the host blood meal appearing limited. This article is protected by copyright. All rights reserved.

Background. Blacklegged ticks (Ixodes scapularis) are important disease vectors in the United States, known to transmit a variety of pathogens to humans, including bacteria, protozoa, and viruses. Their importance as a disease vector necessitates reliable and comparable methods for extracting microbial DNA from ticks. Furthermore, to explore the population genetics or genomics of this tick, appropriate DNA extraction techniques are needed for both the vector and its microbes. Although a few studies have investigated different methods of DNA isolation from ticks, they are limited in the number and types of DNA extraction and lack species-specific quantification of DNA yield. Methods. Here we determined the most efficient and consistent method of DNA extraction from two different developmental stages of I. scapularis-nymph and adult-that are the most important for disease transmission. We used various methods of physical disruption of the hard, chitinous exoskeleton, as well as commercial and non-commercial DNA isolation kits. To gauge the effectiveness of these methods, we quantified the DNA yield and confirmed the DNA quality via PCR of both tick and microbial genetic material. Results. DNA extraction using the Thermo GeneJET Genomic DNA Purification Kit resulted in the highest DNA yields and the most consistent PCR amplification when combined with either cutting or bead beating with select matrices across life stages. DNA isolation methods using ammonium hydroxide as well as the MoBio PowerSoil kit also produced strong and successful PCR amplification, but only for females. Discussion. We contrasted a variety of readily available methods of DNA extraction from single individual blacklegged ticks and presented the results through a quantitative and qualitative assessment.

Ticks and whole blood were collected from American black bears (Ursus americanus Pallas) between October 2011 and October 2012 across four counties in northwestern New Jersey, an area where blacklegged ticks (Ixodes scapularis Say) and their associated tick-borne pathogens are prevalent. Adult American dog ticks (Dermacentor variabilis Say) were the most frequently collected tick species in late spring, whereas adult and nymphal blacklegged ticks were found in both the late spring and fall months. Additionally, for blacklegged ticks, we determined the quality of bloodmeals that females acquired from black bears compared with bloodmeals from white-tailed deer (Odocoileus virginianus Zimmerman), the most important host for the adult stage of this tick species. Measures of fecundity after feeding on each host species were not significantly different, suggesting that the bloodmeal a female blacklegged tick acquires from a black bear is of similar quality to that obtained from a white-tailed deer. These results establish the American black bear as both a host and quality bloodmeal source to I. scapularis. Thus, black bears may help support blacklegged tick populations in areas where they are both present. In addition, samples of black bear blood were tested for DNA presence of three tick-borne pathogens. Anaplasma phagocytophilum Foggie and Babesia microti Franca were found in 9.2 and 32.3% of blood samples, respectively. All blood samples were quantitative polymerase chain reaction-negative for Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt, & Brenner. Although circulating pathogens were found in blood, the status of black bears as reservoirs for these pathogens remains unknown.

Pathogen prevalence within blacklegged ticks (Ixodes scapularis Say, 1821) tends to vary across sites and geographic regions, but the underlying causes of this variation are not well understood. Efforts to understand the ecology of Lyme disease have led to the proposition that sites with higher host diversity will result in lower disease risk due to an increase in the abundance of inefficient reservoir species relative to the abundance of species that are highly competent reservoirs. Although the Lyme disease transmission cycle is often cited as a model for this "dilution effect hypothesis", little empirical evidence exists to support that claim. Here we tested the dilution effect hypothesis for two pathogens transmitted by the blacklegged tick along an urban-to-rural gradient in the northeastern United States using landscape fragmentation as a proxy for host biodiversity. Percent impervious surface and habitat fragment size around each site were determined to assess the effect of landscape fragmentation on nymphal blacklegged tick infection with Borrelia burgdorferi and Anaplasma phagocytophilum. Our results do not support the dilution effect hypothesis for either pathogen and are in agreement with the few studies to date that have tested this idea using either a landscape proxy or direct measures of host biodiversity.

Understanding the role that nymphal and female ticks, Ixodes scapularis, have in the epidemiology of Lyme disease is essential to the development of successful prevention programs. In this study, the authors sought to evaluate the seasonal and annual relations between tick densities and patientsor = 16 years of age diagnosed with erythema migrans (EM), the rash associated with early Lyme disease. Ticks were collected weekly by drag sampling throughout most of the year from 1991 to 1996 in Westchester County, New York. The number of EM cases was based on patients diagnosed at the Westchester County Medical Center using Centers for Disease Control and Prevention (CDC) criteria. No patients with EM were diagnosed from January through April, when only adult ticks were active. Correlation analysis between monthly tick densities and EM incidence was significant for nymphs (r = 0.87, p0.01), but not for adult ticks (r = -0.57, p0.05). There was a strong, although not significant, correlation between peak annual number of patients with EM and peak nymphal tick abundance (r = 0.76, p = 0.08). These data indicate that bites from adult I. scapularis only rarely result in Lyme disease, and that annual nymphal tick abundance determines exposure. This suggests that annual fluctuations in Lyme disease case numbers are largely due to natural changes in tick abundance and, therefore, that control of nymphal I. scapularis should be a major component of Lyme disease prevention efforts.

Effects of deer exclusion on abundance of immature Ixodes scapularis Say parasitizing small and medium-sized mammals, and the role mammals have in introducing ticks to exclosure areas, were examined at two sites in Westchester County, New York. In total, 686 mammal captures representing nine species were obtained, with white-footed mice, Peromyscus leucopus Rafinesque, composing > 80% of all captures, followed by raccoons, Procyon lotor (L.); opossums, Didelphis virginiana (Kerr); and striped skunks, Mephitis mephitis Schreber. At the Near Archives site, 14% of 81 individual mice, 46% of raccoons, and 33% of opossums captured were found to cross the exclosure fence, as did 12% of 50 mice and 38% of raccoons at the Hudson Pines site. Skunks apparently did not cross the fence at either site. Mice captured exclusively outside the Near Archives exclosure hosted significantly more larvae than mice captured inside only, with fence crossers hosting an intermediate number of larvae. At Hudson Pines, numbers of larvae on fence-crossing mice and those captured solely inside the exclosure were equivalent, with tick loads on mice captured outside the exclosure significantly greater. The number of larvae per raccoon did not differ significantly with capture location (inside, outside, or both sides of exclosure fence) at either site. Densities of host-seeking larvae and nymphs were significantly higher outside the exclosure than inside at Near Archives, though not at Hudson Pines. Differences in tick density inside and outside exclosures declined with each successive developmental stage so that adult density inside exclosures tended to converge with that outside at both sites. Although deer exclosures can have a significant impact on nymphal I. scapularis abundance, they may not reduce the risk of encountering infected adults. Mice, raccoons, and opossums have a role in introducing potentially infective ticks to areas where deer have been excluded, though the level of immigration of ticks into the area will likely depend on the density of ticks outside the exclosure.

The effect of deer exclosures upon the numbers of immature Ixodes scapularis Say, the vector of Lyme disease in the eastern United States, was examined at five sites in Westchester County, NY. Study areas ranged in size from 6 to 101 ha where deer had been excluded for a period of 25 yr by > 2.4-m-high fencing that surrounded each site. A total area of 40,506 m2 was drag-sampled during the study to measure tick abundance. Nymphal densities (ticks per 1,000 m2) averaged 4.6 (range, 1.3-9.6) inside exclosures and 27.7 (range, 7.3-79.4) outside. Larval densities averaged 36.7 (range, 1.2-132.1) inside exclosures and 354.4 (range, 7.5-914.5) outside. Comparisons between exclosure sites and outside areas immediately adjacent to the exclosure fence, where deer had unrestricted access, revealed that exclosures had 83% fewer host-seeking nymphs and 90% fewer host-seeking larvae. Tick numbers inside exclosures did not always decline with increasing distance from the fence. There was no significant difference in the rate of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner infection for host-seeking ticks collected inside (20%, n = 50) exclosures compared with ticks collected outside (26%, n = 50) exclosures. Deer fencing may provide a means of significantly reducing the abundance of I. scapularis and the risk of Lyme disease in relatively large areas without the need to reduce or eliminate the deer population.

The efficacy of topically treating white-tailed deer with an acaricide was evaluated in a Lyme disease-endemic community of southern New York State. Twenty-four 4-Poster feeders were placed in a 5.2 km(2) treatment area in Bedford, NY, while a site in Lewisboro, NY, 4.8 km distant, served as control. Treatment periods ran from 15 September to 15 December each fall from 1997 to 2001, and from 15 March to 15 May each spring from 1998 to 2002. Corn consumption averaged 15,779 kg in fall sessions and 9054 kg in spring sessions, and a mean of 89.6% of deer in the study area showed evidence of using the feeders. Deer densities, estimated by aerial snow counts, averaged 22 and 28 deer per km(2) in Bedford and Lewisboro, respectively, over a 3-year period. Significant reductions in tick numbers on deer captured in the treatment area were noted in fall 1999 compared to deer captured at the control site. Drag sampling for nymphal host-seeking ticks indicated 63.6% control in 2001, which dropped to 54.8% the following year, but reached 80% in 2003. Higher-than-normal acorn production in 2001 that likely caused a drop in deer visitation to the feeders may have reduced efficacy against larval ticks in 2002. The 4-Poster effectively reduced the density of Ixodes scapularis, though the level of control is dependent on environmental factors that affect feeding behavior of white-tailed deer.

We evaluated the effects of tick control by acaricide self-treatment of white-tailed deer on the infection prevalence and entomologic risk for three Ixodes scapularis-borne bacteria in host-seeking ticks. Ticks were collected from vegetation in areas treated with the "4-Poster" device and from control areas over a 6-year period in five geographically diverse study locations in the Northeastern United States and tested for infection with two known agents of human disease, Borrelia burgdorferi and Anaplasma phagocytophilum, and for a novel relapsing fever-group spirochete related to Borrelia miyamotoi. Overall, 38.2% of adults and 12.5% of nymphs were infected with B. burgdorferi; 8.5% of adults and 4.2% of nymphs were infected with A. phagocytophilum; and 1.9% of adults and 0.8% of nymphs were infected with B. miyamotoi. In most cases, treatment with the 4-Poster device was not associated with changes in the prevalence of infection with any of these three microorganisms among nymphal or adult ticks. However, the density of nymphs infected with B. burgdorferi, and consequently the entomologic risk for Lyme disease, was reduced overall by 68% in treated areas compared to control areas among the five study sites at the end of the study. The frequency of bacterial coinfections in ticks was generally equal to the product of the proportion of ticks infected with a single bacterium, indicating that enzootic maintenance of these pathogens is independent. We conclude that controlling ticks on deer by self-application of acaricide results in an overall decrease in the human risk for exposure to these three bacterial agents, which is due solely to a reduction in tick density.

From 1997 to 2002, the U.S. Department of Agriculture's Northeast Area-wide Tick Control Project used acaricide-treated 4-Poster Deer Treatment Bait Stations in five eastern states to control ticks feeding on white-tailed deer. The objectives of this host-targeted technology were to reduce free-living blacklegged (Ixodes scapularis Say) and lone star (Amblyomma americanum [L.]) tick populations and thereby to reduce the risk of tick-borne disease. During 2002 to 2004, treatments were suspended, and tick population recovery rates were assayed. Subsequently, the major factors that influenced variations in efficacy were extrapolated to better understand and improve this technology. Treatments resulted in significant reductions in free-living populations of nymphal blacklegged ticks at six of the seven sites, and lone star ticks were significantly reduced at all three sites where they were present. During the study, maximal significant (p < or = 0.05) efficacies against nymphal blacklegged and lone star ticks at individual sites ranged from 60.0 to 81.7 and 90.9 to 99.5%, respectively. The major environmental factor that reduced efficacy was the occurrence of heavy acorn masts, which provided an alternative food resource for deer. Although the 4-Poster technology requires 1 or more years to show efficacy, this host-targeted intervention was demonstrated to be an efficacious, economical, safe, and environment-friendly alternative to area-wide spraying of acaricide to control free-living populations of these tick species.

Summary Ixodes scapularis ticks play an important role in the transmission of a wide variety of pathogens between various mammalian species, including humans. Pathogens transmitted by ticks include Borrelia, Anaplasma and Babesia. Although ticks may harbour both pathogenic and non-pathogenic microflora, little is known about how the diversity of the microflora within ticks may influence the transmission of pathogens. To begin addressing this question, we examined the composition of bacterial communities present in Ixodes scapularis collected from Westchester and Dutchess Counties, New York State, at different developmental and nutritional stages. Genetic fingerprints of bacterial populations were generated by temporal temperature gradient gel electrophoresis (TTGE) separation of individual polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments, followed by DNA sequence analysis for bacterial identification. The fingerprints of the TTGE bands were grouped into five clusters. The most abundant DNA sequence found in all the samples was Rickettsia, followed by Pseudomonas and Borrelia. Ralstonia, Anaplasma, Enterobacterias, Moraxella, Rhodococcus and uncultured proteobacterium were present as well. We also determined the prevalence of Anaplasma phagocytophilum and Borrelia burgdorferi by PCR and DNA sequence analysis. Statistical analyses indicated significant variations in the bacterial communities depending on tick developmental stage and degree of engorgement. We suggest that these two elements affect microbial diversity within the tick and may in turn influence pathogen transmission to humans and animals after tick bite.

Rodent trapping and drag sampling in Van Cortlandt Park, New York City, yielded all stages of Ixodes scapularis, the deer tick vector of Lyme disease and human granulocytic ehrlichiosis (HGE). Polymerase chain reaction analyses of the ticks showed Borrelia burgdorferi and the Ehrlichia sp. that causes HGE.

Ixodes scapularis , the tick vector of Lyme disease and human granulocytic ehrlichiosis (HGE), is prevalent in much of southern New York state. The distribution of this species has increased, as have reported cases of both Lyme disease and HGE. The unreliability of case reports, however, demonstrates the need for tick and pathogen surveillance in order to accurately define areas of high risk. In this study, a total of 89,550 m 2 at 34 study sites was drag sampled in 1995 and a total of 51,540 m 2 at 40 sites was sampled in 1996 to determine tick and pathogen distribution in southern New York state. I. scapularis was collected from 90% of the sites sampled, and regionally, a 2.5-fold increase in nymphal abundance occurred from 1995 to 1996. I. scapularis individuals from all sites were infected with Borrelia burgdorferi in 1995, while an examination of ticks for both B. burgdorferi and the agent of HGE in 1996 confirmed that these organisms were present in all counties; the average coinfection rate was 1.9%. No correlation was found between estimated risk and reported cases of Lyme disease. The geographic disparity of risk observed among sites in this study underscores the need for vector and pathogen surveillance on a regional level. An entomologic risk index can help identify sites for targeted tick control efforts.

Timing of oviposition and larval eclosion for fall- and spring-fed female blacklegged tick, Ixodes scapularis Say, and effect of temperature on those events in southern New York state, where Lyme disease is endemic, were determined in the field. We also examined seasonal pattern of larval host-seeking activity, as well as rate of survival for overwintering, unfed larvae. Totals of 9 and 8 replete female I. scapularis were released in fall 1988 and spring 1989, respectively. For the 10 females that oviposited, egg laying began in mid-to-late May, regardless of when ticks had fed. Likewise, larval eclosion was synchronized in July for all egg masses. Microhabitat temperatures experienced by females were not reliable indicators of female reproductive success, in terms of either presence or absence of eggs, or numbers of larvae recovered. However, average body size was significantly greater for females that oviposited successfully than for those that did not. The percentage of unfed larvae surviving the 8-mo overwintering period from late August to early May ranged from 1.9 to 31.4, with a mean survival rate of 10.4%. Concurrent drag sampling through the year indicated a bimodal pattern of larval abundance marked by a relatively small early peak of activity in late May that extended into early July. Because the first peak of larval activity occurred during the period of oviposition, 8 wk before onset of larval eclosion, it appears that bimodality represents activity of 2 consecutive cohorts, with the early peak composed of overwintering survivors. These data imply variation in timing of reproduction and larval activity from 1 geographic area to another. Efforts to devise a comprehensive scheme for the life cycle of I. scapularis must consider that population differences may exist.

Changes in the abundance of immature Ixodes scapularis Say, the primary vector of Lyme disease, were assessed over a 7-yr period in Westchester County, New York, where the disease is endemic. In total, 4,000 m2 were drag sampled at each of 6 study sites in June and July of 1984 and 1991. The abundance of nymphs collected from all sites was 2.6-fold greater in 1991 than in 1984. Four of the 6 sites had significantly more nymphs in 1991, with increases ranging from 1.1- to 46.5-fold. The abundance of larvae collected from all sites was 34.2-fold higher in 1991 than in 1984. Five of the sites sampled had significantly more larvae in 1991, with increases ranging from 2.7- to 681-fold. These data demonstrate that populations of immature I. scapularis in Westchester County have, overall, increased during the 7-yr period from 1984 to 1991. However, the magnitude of increase is not uniform from site to site.

To the Editor: Human granulocytic ehrlichiosis (HGE), first described in 1994 (1), is the second-most common tick-borne disease in the United States; Lyme disease is the most prevalent. Both diseases are transmitted by blacklegged ticks (Ixodes scapularis Say) that are abundant in southern New York state (2). Factors that influence the risk for infection, particularly the role of wildlife in transmitting the etiologic agent, Anaplasma (formerly Ehrlichia) phagocytophilum (3,4), to vector ticks are not well understood. In the absence of transovarial transmission (5,6), acquisition of A. phagocytophilum by its vector must result either from feeding on the blood of reservoir-competent hosts or by cofeeding of uninfected ticks in close proximity to infected ticks (7).

To the Editor: Human granulocytic ehrlichiosis, a newly discovered tick-borne infection originally described in the upper Midwest,1 has recently been reported in 29 patients from Westchester County, New York.2 We used the polymerase chain reaction (PCR) to examine 173 host-seeking ticks (Ixodes scapularis) collected from vegetation in Westchester County for the presence of the agent of human granulocytic ehrlichiosis, as well as the agent of Lyme disease, Borrelia burgdorferi. After extracting DNA from dissected tissues, we used the 23S ribosomal DNA (rDNA) primers of Schwartz et al.3 for B. burgdorferi and the 16S rDNA primers of Pancholi . . .