New research shows dry‑ice tick traps can capture more ticks than traditional cloth‑dragging, suggesting a faster and potentially more effective way to monitor tick‑borne disease risks. Here, a BanfieldBio research prototype tick trap is deployed by a Texas A&M University team at a field site in Montgomery County, Texas. Trap components from the bottom up are a molded plastic base, a card with downward-facing sticky masking tape, and a foam plastic hamburger container holding 250 grams of dry ice. (Photo by Gabriel Hamer, Ph.D.)

By Ed Ricciuti

Ed Ricciuti

A group of scientists from academia and the private sector hope that the old adage, “Build a better mousetrap, and the world will beat a path to your door”—wrongly attributed to Ralph Waldo Emerson—holds for tick traps, too.

In a study published in December in the Journal of Medical Entomology, they describe how a new commercially viable configuration of an existing research trap could be a more effective tool for surveillance of ticks than the method presently favored, which is to sweep a light-colored piece of fabric through vegetation, either dragging or waving it like a flag.

Tick sampling in the field is a key public health practice for gauging the risk of human exposure to tick-borne diseases (TBDs). These illnesses account for at least three-quarters of the vector-borne infections in the U.S. The national economic burden of diagnosed cases of tick-borne Lyme disease, for example, could be about $1 billion annually.

As the incidence of TBDs rises, so have efforts to improve surveillance techniques, which the public health sector generally admits are far from perfect. The researchers who trialed the new trap say it beats the time-honored dragging and flagging.

Scientists from Washington State University and Texas A&M University collaborated with consultants and a Washington-based research and development company, BanfieldBio, Inc., on the study. Banfield has applied for a patent on a commercial version of the trap, which is lighter and more compact and has other features suitable for commercial use.

Sampling by dragging and flagging is the traditional method for tick surveillance. Here, BanfieldBio research entomologist Jill Joiner, Ph.D., drags for questing ticks. However, new research shows dry‑ice tick traps can capture more ticks than traditional cloth dragging and could serve as an “alternative or supplement to current surveillance methods, pending development of a cost-effective commercial trap.” (Photo by Christopher Downs)

Sampling by dragging and flagging is the only collection method approved by the U.S. Centers for Disease Control and Prevention (CDC) for the four objectives of tick surveillance. These are demonstrating the presence of a tick species and human pathogens in its population, classifying a given county as harboring a particular tick species, establishing the prevalence of human pathogens in tick populations in a county, and documenting cyclical patterns in tick host-seeking behavior and biology. The CDC also considers that dragging and flagging approximates a human walking through tick-infested habitat, says John Borden, Ph.D., a science consultant and senior author of the study.

“Our results strongly suggest that trapping has promise for replacing or supplementing dragging and flagging as a tick surveillance tactic,” Borden and colleagues write. Trapping captured 5.3 times more ticks overall and 1.8 times more ticks per person-hour compared to dragging. The target ticks were so-called hard ticks of the family Ixodidae.

The new research was conducted in Texas, Oklahoma, and Wisconsin, for up to 100 days in spring and summer 2023 across eight sampling sites in each state, and the findings challenge the present wisdom about trapping. Dragging and flagging, say the researchers, are more labor intensive, in that personnel must tromp through the brush covering as much ground as possible, while traps can be left on their own and checked periodically.

Traps potentially catch ticks over long periods of time, even several days, while dragging and flagging snag only ticks that happen to be there at the moment, and could alter habitat, say the researchers. Worse yet, workers engaged in dragging and flagging are vulnerable to catching ticks on their bodies as well as on the cloth they employ.

Of 25,596 ticks collected by the research team, 84.2 percent were caught in traps baited with dry ice, while dragging captured only 15.8 percent. Traps were more effective for catching all life stages of lone star ticks (Amblyomma americanum) and showed similar or superior results for blacklegged ticks (Ixodes scapularis) and American dog ticks (Dermacentor variabilis).

New research shows dry‑ice tick traps can capture more ticks than traditional cloth‑dragging, suggesting a faster and potentially more effective way to monitor tick‑borne disease risks. Shown here is a sticky card removed from a research prototype trap after 24 hours at a research site in Oklahoma, showing a ring of lone star ticks captured on the downward-facing masking tape surface at the apex of the trap base. (Photo by Daniel Marshall, Ph.D.)

One of several findings suggesting that well-designed trapping programs can boost the contribution of tick surveillance to combatting TBDs is that trapping works well when tick numbers are low. The ability of trapping to capture larger numbers of ticks than dragging also suggests that it would be a preferred method to use in estimating the percentage of a tick population that harbors a pathogen at low levels.

When the Lyme disease spirochete Borrelia burgdorferi exists in a large proportion of a tick population, for example, sampling a few hundred ticks may establish the prevalence of infection. At low levels, thousands of ticks may have to be collected and tested to reasonably estimate infection.

The research team described how the traps worked. A bowl served as the base, which had a plastic sheet affixed to it that was sticky on the bottom side. Atop the whole contraption was a reservoir releasing dry ice. Why dry ice? Because, in effect, dry ice expresses itself to a tick’s sensory apparatus as a human or other host on which to fasten and feast. Dry ice is actually compressed and cooled carbon dioxide; when it warms, it sublimates directly to its gaseous form, mimicking the exhalation of a host.

Tiny pits on the first pair of a tick’s forelegs, called Haller’s organs, can detect carbon dioxide from as far a couple of yards. The signal sends a tick questing for a meal, increasing its gait and waving its forelegs for something to grab.

The CDC does recognize traps that use carbon dioxide as a means of documenting the presence of a particular tick or pathogen. The potential downside is that traps tend to catch some species and life stages of ticks more than others and are generally less effective.

“We have been in touch with the CDC,” says Borden. “The CDC is interested in using traps such as ours to determine incidence of pathogen harborage and risk of disease, particularly when populations are low and there is a greater likelihood of capturing a sufficiently large sample by trapping than by dragging.”

There is a hitch to the trap designed by the researchers, which they readily concede: Dry ice is expensive and “poses logistical challenges for field use,” they say; it costs about 60 cents for each 250-gram lure used in the experimental traps. It also must be stored at minus 109.3 degrees Fahrenheit and in a setting that is properly ventilated. Out in the field, this typically means an insulated container that may be too heavy for a long-haul lug. Handlers must also then be careful to avoid frostbite.

The trap tested contained a much smaller amount of dry ice than used by other researchers, making it easier to store and transport and an easier way to contain it. Despite its drawbacks, says Borden, “For the pest control industry, using dry ice is feasible. It can be stored in a cooler in a service truck as long as it is ventilated, with a minimal carry distance to locations where traps may be deployed.” Carbon dioxide also has been produced in traps by various chemical concoctions and fermentation from a mix of yeast and sugar water.

Borden says that the research described in the paper is a partnership between a private company and collaborating researchers common in the medical field but less so in the natural sciences. “Far too often researchers in the natural sciences leave their research too far upstream to attract immediate interest by industry,” he says. “BanfieldBio closes the gap and creates a smooth continuum from curiosity-driven research to commercialization.”

Ed Ricciuti is a journalist, author, and naturalist who has been writing for more than a half century. His most recent book is called Bears in the Backyard: Big Animals, Sprawling Suburbs, and the New Urban Jungle (Countryman Press, June 2014). His assignments have taken him around the world. He specializes in nature, science, conservation issues, and law enforcement. A former curator at the New York Zoological Society, and now at the Wildlife Conservation Society, he may be the only man ever bitten by a coatimundi on Manhattan’s 57th Street.