Effects of Tick-Control Interventions on Tick Abundance, Human Encounters with Ticks, and Incidence of Tickborne Diseases in Residential Neighborhoods, New York, USA

Abstract

L yme disease is an emerging zoonosis caused by the spirochete bacterium Borrelia burgdorferi, which is transmitted between vertebrate hosts, including humans, by ticks in the Ixodes ricinus complex. Annual cases of Lyme disease in the United States, as reported to the Centers for Disease Control and Prevention (1), have grown from a few hundred in the early 1980s to >30,000 in recent years. A recent study estimated that actual clinician diagnoses of Lyme disease in the past decade exceed 450,000 per year (2,3). Increasing incidence over the past few decades reflects both upward trends in case numbers within Lyme diseaseendemic locations and a dramatic geographic spread from both northeastern and Midwestern foci (4-6). Beyond the effects of Lyme disease on human health, economic costs of patient care are estimated at ≈$1 billion/year in the United States (7).Preventing exposure to B. burgdorferi and other tickborne pathogens can be aided by personal practices such as applying repellents, checking for ticks, and avoiding tick habitats. However, the efficacy of these methods is unclear, and considerable differences in effects have been reported (8,9). Although specific methods of property and wildlife management (e.g., deer hunting) are advocated by some agencies (10), knowledge of the effectiveness of these recommendations in reducing human encounters with ticks and incidence of tickborne diseases (TBDs) is limited (11-13).

Risk of tick-borne pathogen spillover into urban yards in New York City

“…It is important to note that while we identify risk factors for tick presence in residential yards, reducing the acarological hazard alone does not necessarily result in a concomitant decrease in the incidence of tick-borne disease. In a recent experiment conducted over 4 years in a residential neighborhood in NYC, two tick control methods effectively reduced the number of questing ticks, ticks on rodents and TBD in pets, but they had no discernable effect on the incidence of human TBDs [ 120 ]. While small sample size per neighborhood, relatively few TBD cases over the study period and variation in human preventative behaviors may have all played a role in decoupling tick abundance from human incidence [ 120 ], the present study highlights the need to better understand the coupling between tick distribution and human exposure behaviors across human-dominated landscapes in order to evaluate where exposure is most frequently occurring.…”

Balsam fir (Abies balsamea) needles and their essential oil kill overwintering ticks (Ixodes scapularis) at cold temperatures

“…Other studies have noted that applications of acaricides prior to re-activation of ticks in the spring can significantly reduce the numbers of early season ticks 11 , suggesting that reducing overwintering survival will reduce numbers in the spring 60 . For example, Rand et al 61 found that a low toxicity acaricide (i.e., IC2™, formulation based on rosemary essential oil) sprayed in October substantially reduced the number of I. scapularis ticks in the following spring.…”

Vector-Borne Viral Diseases as a Current Threat for Human and Animal Health—One Health Perspective

“…Inside the traps, animals are brushed with acaricids. This method was found to effectively reduce the population of larval stages of ticks [ 163 ]. Although chemical control methods proved to be effective in vector-borne disease control, there are growing concerns about their further use due to their potential negative effect on human health and the emergence of resistance in targeted vector populations [ 164 ].…”