Abstract
As human cases of tick-borne disease continue to increase, there is a heightened imperative to collect data on human-tick encounters to inform disease prevention. Passive tick surveillance programs that encourage members of the public to submit ticks they have encountered can provide a relatively low-cost means of collecting such data. We report the results of 11 years of tick submissions (2006–2016) collected in Monmouth County, New Jersey, an Atlantic coastal county long endemic for Lyme disease. A total of 8,608 ticks acquired in 22 U.S. states were submitted, 89.7% of which were acquired in Monmouth County, from 52 of the County’s 53 municipalities. Seasonal submission rates reflected known phenology of common human-biting ticks, but annual submissions of both Amblyomma americanum and Dermacentor variabilis increased significantly over time while numbers of Ixodes scapularis remained static. By 2016, A. americanum had expanded northward in the county and now accounted for nearly half (48.1%) of submissions, far outpacing encounters with I. scapularis (28.2% of submissions). Across all tick species and stages the greatest number of ticks were removed from children (ages 0–9, 40.8%) and older adults (ages 50+, 23.8%) and these age groups were also more likely to submit partially or fully engorged ticks, suggesting increased risk of tick-borne disease transmission to these vulnerable age groups. Significantly more people (43.2%) reported acquiring ticks at their place of residence than in a park or natural area (17.9%). This pattern was more pronounced for residents over 60 years of age (72.7% acquired at home). Education that stresses frequent tick checks should target older age groups engaged in activity around the home. Our results strongly suggest that encounter rates with ticks other than I. scapularis are substantial and increasing and that their role in causing human illness should be carefully investigated.
Highlights
Lyme disease (LD), caused by the bacterium Borrelia burgdorferi, is the most commonly reported vector-borne disease in the United States with most cases reported from areas of traditionally high incidence in the Northeast, mid-Atlantic, and upper Midwest regions where case rates have remained stable or decreased during the reporting period 2008–2015 [1]
After analysis showed no autocorrelation for series (P > 0.05), we examined correlation between numbers of LD-infected I. scapularis nymphs and reported LD case rates for Monmouth County and total tick submissions over time using Pearson correlation coefficients [37]
We observed a dramatic change in the species composition of tick submissions over time, with submissions of both A. americanum and D. variabilis increasing over the period 2006–2016 while I. scapularis submissions remained comparatively flat
Summary
Lyme disease (LD), caused by the bacterium Borrelia burgdorferi, is the most commonly reported vector-borne disease in the United States with most cases reported from areas of traditionally high incidence in the Northeast, mid-Atlantic, and upper Midwest regions where case rates have remained stable or decreased during the reporting period 2008–2015 [1]. Additional focus in recent years has centered on underrecognition of ehrlichiosis cases [6, 7] and emergence of new viruses [8] transmitted by the lone star tick, Amblyomma americanum. Many of these expanding and emerging disease agents have been identified in ticks collected from New Jersey [9, 10]. Pepin et al [11] demonstrated a positive correlation between density of infected nymphs in I. scapularis and LD across more than 300 locations in the Northeast and Midwest, but were unable to consistently predict LD cases using tick collection data in areas where LD was emergent
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