Bioassays to evaluate non-contact spatial repellency, contact irritancy, and acute toxicity of permethrin-treated clothing against nymphal Ixodes scapularis ticks

Abstract

Summer-weight clothing articles impregnated with permethrin are available as a personal protective measure against human-biting ticks in the United States. However, very few studies have addressed the impact of contact with summer-weight permethrin-treated textiles on tick vigor and behavior. Our aim was to generate new knowledge of how permethrin-treated textiles impact nymphal Ixodes scapularis ticks, the primary vectors in the eastern United States of the causative agents of Lyme disease, human anaplasmosis, and human babesiosis. We developed a series of bioassays designed to: (i) clarify whether permethrin-treated textiles impact ticks through non-contact spatial repellency or contact irritancy; (ii) evaluate the ability of ticks to remain in contact with vertically oriented permethrin-treated textiles, mimicking contact with treated clothing on arms or legs; and (iii) determine the impact of timed exposure to permethrin-treated textiles on the ability of ticks to move and orient toward a human finger stimulus, thus demonstrating normal behavior. Our results indicate that permethrin-treated textiles provide minimal non-contact spatial repellency but strong contact irritancy against ticks, manifesting as a “hot-foot” effect and resulting in ticks actively dislodging from contact with vertically oriented treated textile. Preliminary data suggest that the contact irritancy hot-foot response may be weaker for field-collected nymphs as compared with laboratory-reared nymphs placed upon permethrin-treated textile. We also demonstrate that contact with permethrin-treated textiles negatively impacts the vigor and behavior of nymphal ticks for > 24 h, with outcomes ranging from complete lack of movement to impaired movement and unwillingness of ticks displaying normal movement to ascend onto a human finger. The protective effect of summer-weight permethrin-treated clothing against tick bites merits further study.

Management Options for Ixodes ricinus-Associated Pathogens: A Review of Prevention Strategies

“…Repellents can also dramatically decrease the risk of tick attachment [60,61] and for optimal benefit, proper application of repellents should include consideration for the concentration of active compound and the duration of activity. Modern synthetic anti-tick repellents which can be applied directly on the human skin frequently contain N,N-diethyl-m-toluamide (DEET), ethyl butylacetyl-aminopropionate (IR3535) or 1-piperidinecarboxylic acid (picardin), as primary active ingredients.…”

Impact of Wearing and Washing/Drying of Permethrin-Treated Clothing on Their Contact Irritancy and Toxicity for NymphalIxodes scapularis(Acari: Ixodidae) Ticks

“…1) and placed within a horizontal petri dish, for a predetermined period of time. In this study, ticks were held in continuous contact with test textiles (prevented from moving off of the test textile) for 30, 60, or 120 s. These contact durations were found previously to severely impact the vigor of I. scapularis nymphs (Eisen et al 2017b). For trials with laboratory-reared nymphs, each combination of test textile and exposure time was challenged with three groups of 10 ticks, for a total of 30 ticks (grand total of 2,320 ticks).…”

“…The contact irritancy and toxicity bioassays used to evaluate the impact of test textiles on I. scapularis nymphs were conducted using methods described in detail previously (Eisen et al 2017b). Briefly, the contact irritancy assay employed a playing card (64 mm wide by 89 cm tall) covered by a solid piece of test textile (Fig.…”

“…A seminal study by Miller et al (2011), where human volunteers allowed themselves to receive tick bites, demonstrated that wearing permethrin-impregnated clothing (shoes, socks, shorts, and shirts) not only reduced the number of laboratory-reared I. scapularis nymphs that attached to human volunteers but also led to the majority of attached nymphs dying within hours of their attachment. We further demonstrated that permethrin-impregnated clothing, in the form of shirts, pants, and socks from Insect Shield, LLC (Greensboro, NC), has both contact irritant and toxicant effects on I. scapularis nymphs (Eisen et al 2017b, Prose et al 2018). However, published studies are lacking for how wearing and washing/drying of permethrin-impregnated clothing may impact their contact irritancy and toxicity for I. scapularis nymphs.…”

Essential oils as tick repellents on clothing

“…They work, generally, by producing an irritant effect which causes questing ticks to avoid treated clothing or skin completely, or to fall off soon after contact with the treated surface (Halos et al 2012). This definition is akin to 'contact irritancy', defined by Grieco et al (2007) for mosquito repellents, which has recently been used in the context of ticks (Eisen et al 2017). In practice a repellent could also describe a compound that simply prevents acquired ticks from biting, although this form of repellency is rarely encountered (Halos et al 2012).…”