Spatial repellents transfluthrin and metofluthrin affect the behavior of Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis in an in vitro vertical climb assay

Authors: SIEGEL, ERIC - University Of Massachusetts; OLIVERA, MARCOS - Institute Technology Of Buenos Aires (ITBA); ROIG, ESTEBAN - Institute Technology Of Buenos Aires (ITBA); PERRY, MELYNDA - The Us Army Combat Capabilities Development Command Soldier Center; Li, Andrew; D'HERS, SEBASTIAN - Institute Technology Of Buenos Aires (ITBA); ELMAN, NOEL - Gearjump Technologies, Llc; RICH, STEPHEN - University Of Massachusetts

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2022
Publication Date: 11/8/2022
Citation: Siegel, E.L., Olivera, M., Roig, E.M., Perry, M., Li, A.Y., D'Hers, S., Elman, N.M., Rich, S.M. 2022. Spatial repellents transfluthrin and metofluthrin affect the behavior of Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis in an in vitro vertical climb assay. PLOS ONE. 17(11):e0269150. https://doi.org/10.1371/journal.pone.0269150.
DOI: https://doi.org/10.1371/journal.pone.0269150

Interpretive Summary: Ticks are the principal arthropod vectors of a variety of human, livestock, and companion animal disease in North America, such as Lyme disease, Anaplasmosis, and Babesiosis. Chemical repellents, including volatile spatial repellents, have been used effectively as a personal protection measure against mosquitoes and other blood-feeding flying insects. Due to ticks’ unique host-seeking behavior, it is hard to measure the effectiveness of chemical repellents in reducing the risk of tick bites. USDA-ARS scientists joined a research team including university, industry, and international researchers to develop a novel tick bioassay technique for evaluation of spatial repellents against three medically important tick species (the blacklegged tick, the lone star tick, and the American dog tick) in the northeastern United States. Data generated from combined use of a vertical tick climbing assay and a computer-based video tracking and analysis system indicate all repellent compound inhibited tick climbing. Two volatile repellent compounds, transfluthrin and metofluthrin, were particularly effective against the lone star tick and the American dog tick. This was the first attempt to understand how ticks respond to spatial repellents in a laboratory setting. The results generated from this study would aid efforts in developing new controlled release repellent products to better protect the U.S. military personnel and public health.

Technical Abstract: Repellents serve an important role in bite protection. Tick repellents largely rely on biomechanisms that induce responses with direct contact, but synthetic pyrethroids used as spatial repellents against insects have received recent attention for potential use in tick protection systems. An in vitro vertical climb assay was designed to assess spatial repellency against Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis adult, female ticks. Climbing behavior was assessed with and without the presence of two spatial repellents, transfluthrin and metofluthrin. Repellency parameters were defined to simulate the natural questing behavior of ambushing ticks, including measures of detachment, pseudo-questing duration, climbing deterrence, and activity. Significant effects were observed within each parameter. D. variabilis showed the greatest general susceptibility to each repellent, followed by A. americanum, and I. scapularis. The most important and integrative measure of repellency was climbing deterrence–a measure of the spatial repellent’s ability to disrupt a tick’s natural propensity to climb. Transfluthrin deterred 75% of D. variabilis, 67% of A. americanum, and 50% of I. scapularis. Metofluthrin was slightly more effective, deterring 81% of D. variabilis, 73% of A. americanum, and 72% of I. scapularis. The present study poses a novel paradigm for repellency and reports a preliminary assessment of spatial repellent effect on tick behavior. Further research will assess spatial repellency in a more natural setting, scale exposure conditions, and incorporate host cues.