Robert A. Jordan

Relative Encounter Frequencies and Prevalence of Selected Borrelia, Ehrlichia, and Anaplasma Infections in Amblyomma americanum and Ixodes scapularis (Acari: Ixodidae) Ticks from Central New Jersey

Abstract To evaluate their relative importance in tick-borne disease transmission in New Jersey, host-seeking Amblyomma americanum (L.) and Ixodes scapularis Say adults and nymphs were collected during spring activity periods in 2003 and 2004 to determine relative frequencies at which these ticks were encountered from an area known to be hyperendemic for Lyme disease. Although similar numbers of the two species were encountered during early spring of both years, A. americanum were encountered more often later in the season and exhibited a longer activity period than I. scapularis. A. americanum nymphs were collected at frequencies between 2.6 and 7.3 times higher than I. scapularis nymphs. Polymerase chain reaction (PCR) analysis of 121 A. americanum adults yielded infection prevalences of 9.1% for Borrelia lonestari, 12.3% for Ehrlichia chaffeenensis, and 8.2% for E. ewingii, and coinfection prevalences of 4.1% for E. chaffeensis/E. ewingii and 0.8% for E. chaffeensis/B. lonestari. Infection prevalences in 147 I. scapularis adults were 50.3% for B. burgdorferi, 6.1% for Anaplasma (Ehrlichia) phagocytophilum, and 1.4% for a recently described novel Borrelia species, whereas the coinfection prevalences were 2.7% for B. burgdorferi/A. phagocytophilum, 0.7% for B. burgdorferi/novel Borrelia, and 0.7% for A. phagocytophilum/novel Borrelia. The B. burgdorferi infection prevalence in I. scapularis was considerably higher than that in A. americanum. However, the higher A. americanum encounter frequencies compared with I. scapularis may result in increased risk of acquiring exposure to A. americanum-transmitted pathogens. The potential public health implications of these results are discussed.

Effects of Selected Meteorological Factors on Diurnal Questing of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae)

Abstract The diurnal questing behavior of adult Ixodes scapularis Say and Amblyomma americanum (L.) were monitored in the field to determine whether ticks would be collected with greater frequency during certain times of the day and under certain ambient meteorological conditions. Temperature and relative humidity explained a significant amount of the total variation in tick collections. Although both species were collected during every period, I. scapularis adults tended to quest earlier and later in the day when temperatures were lower and relative humidity higher, whereas A. americanum were collected with greater frequency in late morning and early afternoon during periods of higher temperatures and lower humidity. Questing of I. scapularis adults was observed at temperatures as low as -0.6°C, whereas no adult A. americanum were collected below 4.4°C. The questing temperature threshold for I. scapularis adults observed in this study was below that reported previously. The implications of these temporal activity patterns on the assessment of disease transmission risk and sampling bias are also discussed.

Ability of Two Natural Products, Nootkatone and Carvacrol, to Suppress Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) in a Lyme Disease Endemic Area of New Jersey

ABSTRACT We evaluated the ability of the natural, plant-derived acaricides nootkatone and carvacrol to suppress Ixodes scapularis Say and Amblyomma americanum (L.) (Acari: Ixodidae). Aqueous formulations of 1 and 5% nootkatone applied by backpack sprayer to the forest litter layer completely suppressed I. scapularis nymphs through 2 d. Thereafter, the level of reduction gradually declined to ≤50% at 28 d postapplication. Against A. americanum nymphs, 1% nootkatone was less effective, but at a 5% concentration, the level of control was similar or greater to that observed with I. scapularis through 21 d postapplication. Initial applications of 0.05% carvacrol were ineffective, but a 5% carvacrol formulation completely suppressed nymphs of both species through 2 d and resulted in significant reduction in I. scapularis and A. americanum nymphs through 28 and 14 d postapplication, respectively. Backpack sprayer applications of 5% nootkatone to the shrub and litter layers resulted in 100% control of I. scapularis adults through 6 d, but the level of reduction declined to 71.5% at 28 d postapplication. By contrast, high-pressure applications of 2% nootkatone to the litter layer resulted in 96.2–100% suppression of both I. scapularis and A. americanum nymphs through 42 d, whereas much lower control was obtained from the same formulation applied by backpack sprayer. Backpack sprayer application of a 3.1% nootkatone nanoemulsion resulted in 97.5–98.9 and 99.3–100% reduction in I. scapularis and A. americanum nymphs, respectively, at 1 d postapplication. Between 7 d and 35 d postapplication, the level of control varied between 57.1% and 92.5% for I. scapularis and between 78.5 and 97.1% for A. americanum nymphs. The ability of natural products to quickly suppress and maintain significant control of populations of these medically important ticks at relatively low concentrations may represent a future alternative to the use of conventional synthetic acaricides.

Meteorologically Mediated Diurnal Questing of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) Nymphs

Abstract Questing Ixodes scapularis Say and Amblyomma americanum (L.) nymphs were collected in the field by drag sampling to determine whether ticks would be collected in greater numbers during certain times of the day and under certain ambient meteorological conditions. Ticks were collected hourly for 16 h on 4 d and counts were contrasted with simultaneous measurements of ambient temperature and relative humidity, and with similar measurements made within the leaf litter. Peak numbers of questing I. scapularis and A. americanum nymphs were collected at distinctly different times of day, suggesting that the two species were responding to different environmental conditions. Both species demonstrated responses to diel changes in local meteorological conditions. Numbers of ticks were correlated with ambient temperature and humidity and with conditions recorded in the leaf litter that appeared to play a significant role in mediating questing behavior of both species. The time of day when tick sampling is conducted might significantly bias population estimates for sympatric species and the assessment of tick-borne disease transmission risk.

Efficacy of Granular Deltamethrin Against Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) Nymphs

Abstract A single barrier application of granular deltamethrin to the woodland edges of a forested residential community in late spring significantly reduced the abundance of Ixodes scapularis Say nymphs. The application also suppressed the population of Amblyomma americanum (L.) nymphs, which recently became established in the study area. The efficacy of deltamethrin is compared with other commonly used acaricides.

Effects of Reduced Deer Density on the Abundance of Ixodes scapularis (Acari: Ixodidae) and Lyme Disease Incidence in a Northern New Jersey Endemic Area

Abstract We monitored the abundance of Ixodes scapularis Say (Acari: Ixodidae) and the Lyme disease incidence rate after the incremental removal of white-tailed deer, Odocoileus virginianus Zimmermann, within a suburban residential area to determine whether there was a measurable decrease in the abundance of ticks due to deer removal and whether the reduction in ticks resulted in a reduction in the incidence rate within the human population. After three seasons, the estimated deer population was reduced by 46.7%, from the 2002 postfawning estimate of 2,899 deer (45.6 deer per km2) to a 2005 estimate of 1,540 deer (24.3 deer per km2). There was no apparent effect of the deer culling program on numbers of questing I. scapularis subadults in the culling areas, and the overall numbers of host-seeking ticks in the culling areas seemed to increase in the second year of the program. The Lyme disease incidence rate generated by both passive and active surveillance systems showed no clear trend among years, and it did not seem to vary with declining deer density. Given the resources required to mount and maintain a community-based program of sufficient magnitude to effectively reduce vector tick density in ecologically open situations where there are few impediments to deer movement, it may be that deer reduction, although serving other community goals, is unlikely to be a primary means of tick control by itself. However, in concert with other tick control interventions, such programs may provide one aspect of a successful community effort to reduce the abundance of vector ticks.

Effects of Microscale Habitat Physiognomy on the Focal Distribution of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) Nymphs

Abstract The focal distribution of Ixodes scapularis Say and Amblyomma americanum (L.) was measured at 10-m intervals across the 1-ha study area placed within a mixed hardwood-pine forest with a sparse to dense shrub layer. At each of the resulting 100 locations, 1-m2 plots were established and, following characterization of vegetation and edaphic conditions, were periodically flagged throughout the nymphal tick season. I. scapularis and A. americanum nymphs appeared to be nonrandomly distributed within the forested study area. Although only a few I. scapularis nymphs were collected overall, several locations consistently yielded more A. americanum nymphs than the remaining sites. I. scapularis was found in plots with substantial shrub density, extensive leaf litter, and deep soil duff layers, all of which contribute to creating high-humidity conditions for questing ticks. Questing A. americanum were more frequently encountered in more open canopy situations with less dense shrub layers and significantly reduced litter and duff layers. A. americanum appears to be more tolerant of desiccating conditions and so is able to occupy microsites or microhabitats that are less favorable for sympatric I. scapularis. The implications of these findings on the ability to sample ticks and estimate disease transmission risk are discussed.

Integrated Use of 4-Poster Passive Topical Treatment Devices for Deer, Targeted Acaricide Applications, and Maxforce TMS Bait Boxes to Rapidly Suppress Populations of Ixodes scapularis (Acari: Ixodidae) in a Residential Landscape

Abstract In fall 2003, we began testing an integrated control strategy to rapidly achieve and sustain reduced numbers of Ixodes scapularis Say (Acari: Ixodidae) in a residential area. We combined two host-targeted technologies in conjunction with single, barrier acaricide applications to sequentially attack each postembryonic life stage of the tick. Granular deltamethrin applied to the lawn–forest interface of participant properties resulted in 100% control of host-seeking nymphs. Nymphal and larval tick burdens on targeted small mammal hosts at treated properties were reduced by 92.7 and 95.4%, respectively, after the first year (2004) of combined interventions. Over the same period, populations of host-seeking nymphs, larvae, and adults were reduced by 58.5, 24.8, and 77.8%, respectively. After interventions in 2005, tick burdens on small mammals were maintained at similar levels, whereas control of host-seeking nymphs, larvae, and adults increased to 94.3, 90.6, and 87.3%, respectively. Prospects for widespread use of these technologies to protect the public’s health are discussed.

Influence of Meso- and Microscale Habitat Structure on Focal Distribution of Sympatric Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae)

Abstract We compared the distribution of sympatric Ixodes scapularis Say and Amblyomma americanum (L.) within several suitable forested habitats at different spatial scales and characterized differences in microhabitat features accounting for the observed distribution of questing ticks. We used automatic data loggers placed in the shrub and litter layers to contrast mesoclimate and microclimate conditions experienced by questing ticks. Larger numbers of I. scapularis were collected at sites where the forest canopy was more fragmented and where the canopy contained more hardwood species than pitch pine, Pinus rigida Mill. Dominance of pine in the canopy affected the character of the shrub layer vegetation and composition of the litter layer, which concomitantly affected the microclimate conditions experienced by questing ticks. Pitch pine-dominated habitats were drier and hotter than those under a broad-leaved canopy, and questing ticks experienced increased saturation deficit in the later spring and summer in pine forest sites. The shrub layer vegetation seemed to have a moderating effect on the microclimate experienced by questing ticks and subtle differences in vegetation structure resulted in substantially different conditions as encountered by questing ticks over the space of a few meters. In contrast to questing I. scapularis, all three stages of questing A. americanum exhibited poor relationships with microclimate variables recorded in the litter and shrub layers. Further research is required to determine which environmental conditions and which habitats are most likely to support this species.

Effects of Barrier Application of Granular Deltamethrin on Subadult Ixodes scapularis (Acari: Ixodidae) and Nontarget Forest Floor Arthropods

Abstract We evaluated the effects of a single application of granular deltamethrin made against nymphal Ixodes scapularis Say on the diversity and abundance of forest arthropods taken in pitfall traps in oak forest sites for 16 wk after treatment in central New Jersey. Control of I. scapularis subadults on treated plots ranged between 97 and 100% and continued at least 12 wk postapplication. Significant short-term changes in arthropod assemblages were detected at one of three study sites within 4 wk posttreatment. Effects were not distributed equally across taxa. Seasonal changes in numbers and diversity of forest arthropods in the study areas may have affected the impact of the acaricide in the treatment area. Comparison with control areas indicated that reductions in abundance of some arthropod taxa in the treatment area were detectable 12 wk after treatment. Total arthropod species diversity was not significantly affected by the application, and no treatment effects were detected 16 wk postapplication, suggesting that the arthropod community had recovered from the effects of the application. The merits of barrier applications in integrated tick control programs are discussed.