The BiteBarrier perimeter: A passive spatial device for tick control and bite prevention

Abstract

Tick-borne diseases (TBDs) impact human and animal health on a global scale. Prevention of TBDs relies primarily on prevention of tick bites. New bite-prevention technologies are needed as an alternative to current approaches such as topical repellents and treated clothing which suffer low user compliance. To date, no passive spatial devices have been commercialized for area protection against ticks. The BiteBarrier (formerly the Personal Insect Repellent Kit, PIRK), a passive, lightweight device that emits transfluthrin, offers to fill this gap. In a previous study, we demonstrated contact toxicity of the BiteBarrier substrate to three tick species, Ixodes scapularis, Dermacentor variabilis and Amblyomma americanum, and reported differences in efficacy depending on species and short-range spatial efficacy against I. scapularis adult females. Here, we extended analyses and demonstrated modest spatial activity of the BiteBarrier substrate against A. americanum and D. variabilis adult females. Using a dual-choice behavioral assay, we showed that the three tick species preferred an area of untreated substrate. Lastly, we present a novel perimeter assay, developed to assess the efficacy of the BiteBarrier ground-based prototype against ticks. At short-range in a Peet Grady-style chamber, the BiteBarrier perimeter induced greater than 90% knockdown of I. scapularis adult females at 1 and 2 h post-exposure and 90% mortality at 48 h post-exposure. Taken together, study findings indicate the potential of the BiteBarrier perimeter to control ticks at near range and potentially, to protect against tick bites.

Keywords: BiteBarrier; Ixodes scapularis; Passive spatial device; Tick; Tick-bite prevention; Transfluthrin.

Graphical abstract

Fig. 1

Schematic of the horizontal behavioral choice assay to assess the capability of the BiteBarrier substrate to disrupt host-seeking and bite behaviors of adult female I. scapularis, A. americanum, and D. variabilis, in the presence of a host. The assay consists of a Petri dish lined with treated substrate and untreated (control) substrate (no AI). The Introduction zone comprises a 1.5 × 1.5 cm square of untreated filter paper placed on the substrates in the center of the dish. The finger of a volunteer is introduced via a hole in the lid of the Petri dish. The location of ticks (Introduction zone, BiteBarrier treated substrate + Host Zone, BiteBarrier substrate Control (no AI) Zone) is recorded at 1-min intervals for up to 5 min. All assays comprise n = 3 technical replicates per biological replicate, with n = 3 biological replicates (three individual volunteers/biological replicate, and same volunteers for control and treated ticks).

Fig. 2

Schematic of the perimeter assay to assess the spatial activity of the BiteBarrier perimeter to I. scapularis adult females. The BiteBarrier perimeter comprising either untreated substrate (control) or treated BiteBarrier, dimensions: 12.5 cm width; 125 cm length × 125 cm height, was placed on a white ground sheet, edged with duct tape, which had the sticky surface exposed to prevent the escape of ticks. The BiteBarrier was acclimated for 2 h, and 10 adult female ticks were introduced and placed in the lower-left corner at 1 cm equidistance from the edge of the substrate.

Fig. 3

Spatial efficacy and repellency of the BiteBarrier substrate (location in the test arena) to A. americanum and D. variabilis adult females in an enclosed test arena assessed using a modular assay. The bar graphs indicate the percent of ticks located in each of the four quadrants (Q1-Q4) at 30-min intervals up to 120 min during exposure of A. americanum (A, B) and D. variabilis (C, D) in the test arena. Q1 is the quadrant closest (colored in red) and Q4 the farthest (colored in gray) to the BiteBarrier substrate. Bar graph colors correspond to Q1-Q4. Error bars are cut at the y-axis maximum.

Fig. 4

Spatial efficacy of the BiteBarrier substrate (location and knockdown in test arena) to D. variabilis and A. americanum adult females in an enclosed chamber assessed using a modular assay. A Bar graph indicating the percent of control and treated D. variabilis females located in each of the four quadrants of the test arena at 30 min exposure. B Bar graph indicating the percent knockdown (KD) of A. americanum females at 10-min intervals up to 120 min exposure in the test arena. Q1 is the quadrant closest and Q4 the farthest to the BiteBarrier substrate. The results represent n = 3 independent biological replicates, with n = 3 technical replicates per biological replicate. Two-way ANOVA with Šídák’s multiple comparison test (P < 0.05) was used to compare the two groups (∗P < 0.05; ∗∗P < 0.005; ∗∗∗∗P < 0.0001).

Fig. 5

Impact of the BiteBarrier substrate on the location of adult I. scapularis, A. americanum and D. variabilis in the test arena during forced exposure in the horizontal behavioral choice assay. Bar graphs show the percent of adult females of I. scapularis (A), A. americanum (B), and D. variabilis (C) in the different locations of the test arena (Introduction Zone, BiteBarrier substrate + Host Zone, BiteBarrier substrate Control (no AI) Zone) at 1-min intervals up to 5 min. Results represent n = 3 independent biological replicates (15 ticks/biological replicate). Error bars are cut at the y-axis maximum. See Supplementary Tables S3–S5 for statistical analyses.

Fig. 6

Impact of the BiteBarrier perimeter on the location of adult I. scapularis females at the end of the forced exposure period in a Peet Grady-style Chamber. The bar graph shows the percent of ticks in the different areas of the test arena (inner area, perimeter device, outer area) at the start and at the end of the 120-min exposure. Results represent n = 3 independent biological replicates (10 ticks/biological replicate). Error bars are cut at the y-axis maximum. Two-way ANOVA with Tukey’s multiple comparison test (P < 0.05) was used to compare the location of I. scapularis females in the test arena (inner area, perimeter device, outer area) at 120 min for control and treated groups (∗P < 0.05). Abbreviations: C, control; T, treated (BiteBarrier-exposed).

Fig. 7

Spatial efficacy of the BiteBarrier perimeter to I. scapularis adult females in a forced exposure assay in a Peet Grady-style chamber. Bar graphs show percent KD (A) and percent mortality (B) of ticks at 1, 2, 24, and 48 h post-exposure for control and treated groups. Error bars are cut at the y-axis maximum. The results represent n = 3 independent biological replicates with n = 3 technical replicates per biological replicate. Two-way ANOVA with Šídák’s multiple comparison test (P < 0.05) was used to compare the two groups (∗P < 0.05; ∗∗P < 0.005; ∗∗∗∗P < 0.0001).