New tool may offer better way to prevent tick bites

controlled-release device (CRD). Credit: one more (2022). DOI: 10.1371/journal.pone.0269150

When it comes to preventing tick bites—especially dramatically, in light of the decade-long increase in tick-borne diseases—bug sprays help but are less than optimal.

For example, DEET was designed to prevent fast-moving mosquitoes from landing on their host, where they bite and fly away in seconds. Ticks, on the other hand, do not fly, but ambush and then slowly climb onto their host until they embed, feed and can live for several days.

“Unfortunately, most repellents were developed for mosquitoes more than 75 years ago and not for tick“Vector-borne disease specialist Stephen Rich, professor of microbiology at the University of Massachusetts Amherst and executive director of the UMass Amherst-based New England Center of Excellence in Vector-borne Diseases (NEWVEC). Works, but a holy grail would be to have another repellent tool—not a contact repellent like DEET, but a spatial repellent—that works as well or better than DEET against ticks.”

Experiments at the Rich Laboratory of Medical Zoology used a new controlled-release device developed by scientist-entrepreneur Noel Allman. Rich and colleagues tested the effects on ticks after dropping the synthetic pyrethroids transfluthrin and metofluthrin into a small, transparent chamber equipped with three vertical climbing sticks. Ticks do not come into direct contact with repellents; Rather, the active ingredients create more of a “force field” that alters and slows the tick’s progress toward their target.

Experimental setup. The controlled release device was placed in the upper left corner of the experiment chamber. Three vertical climbing sticks were placed along the top face. A camera recorded tick climbing from the perspective shown for quantitative behavioral analysis based on vertical movement. Credit: one more (2022). DOI: 10.1371/journal.pone.0269150

The results, published today, November 8, in the journal one morefound that two spatial repellents were effective in changing the behavior of ticks, making them less likely to climb vertically and more likely to detach or fall off the stick.

“While we still have much work to do, these innovative findings substantiate the theory that these spatial repellants alter behavior in a way that we hope will reduce tick bitesays senior author Rich.

The paper’s lead author, Eric Siegel, helped design the vision system that accurately tracked tick movement in the experiment room. “People throw the term ‘repelency’ around a lot, and we’ve made it a goal to redefine tick protection and find ways to measure it,” says Siegel, a lab technician who holds her Ph.D. Studies in microbiology under Rich. “There’s a lot we still don’t know about tick olfaction [smell] more delicious [taste] mechanism, and this was the biggest challenge in these experiments, as in the development of protective products as a whole.”

The compounds were tested against three main human-biting ticks in the US: I. scapularis (black-legged or deer tick), which can spread Lyme disease and anaplasmosis, among other diseases; D. variabilis (American dog tick), which can transmit Rocky Mountain spotted fever and tularemia; and A. americanus (lone star tick), which can spread ehrlichiosis and is linked to an allergy to red meat.

Concentration gradient from CFD simulation, 25 min after release. Concentration gradients produced from CFD simulations of (a) transfluthrin, and (b) metofluthrin, were plotted at 25 min after release. Concentrations represent tick exposure halfway through the test (5 min), accounting for an induction time of 20 min prior to tick introduction. A vertical concentration gradient was observed, with high concentrations (warm colors) present at the bottom of the chamber and low concentrations (cold colors) at the top. Two perspectives were depicted: viewing the chamber from the camera’s point of view (right) and the side with the CRD (left). The CRD was located in the upper left corner from the right box perspective and in the upper middle of the side perspective. Credit: one more (2022). DOI: 10.1371/journal.pone.0269150

Experiments found that transfluthrin killed 75% of D. variabilis, 67% A. americanum and 50% I. scapularis stopped. Metofluthrin was slightly more effective, 81% in D. Variabilis, 73% of A. American and 72% I. Inhibits scapularis.

“We were impressed not only with the repellent but behavior change in ticks,” says co-author Ellman, founder and CEO of GearJump Technologies, which designed a controlled-release device that can attach to soldiers’ boots. Many ticks in experiments were slower-moving, less mobile, and on paper. According to it appeared in a “drunken state”.

Elman contacted Rich a few years ago to design and run experiments using the device with various repellents. The next step is to experiment with real animal hosts.

“Repellents probably won’t stop ticking us off,” Rich says. “We hope the repellent will help them stay on us, and that’s where the battle lines really need to be drawn.”

Researchers can imagine a day when such devices will be commercially available to the general public. Until then the research will continue. “We still mostly don’t know how the chemicals we use work,” Siegel says. “When we do that, we can develop and refine these measures in a more targeted way.”