Ticks are a nuisance across many areas of the U.S., capable of spreading harmful pathogens to both animals and humans. A new study led by researchers at Penn State analyzed the effectiveness of a simple, inexpensive strategy for controlling ticks that homeowners can use in their backyards.
The researchers examined the efficacy of tick tubes for removing ticks from mice. Tick tubes are small cardboard tubes stuffed with cotton batting treated with specialized permethrin, a commonly used insecticide extracted from the chrysanthemum flower that kills ticks but is safe for humans and mammals. Mice gather the treated cotton batting to line their nests, which transfers the permethrin to their fur. This is then fatal for ticks that attempt to feed on the treated mice.
The study, recently published in the Journal of Medical Entomology, found that the tubes were effective at reducing the number of ticks on mice within one season, and that mice's use of tick tubes increased over time, suggesting that mice become more comfortable using them the longer they remain in the area.
Additionally, the researchers found that tubes needed to be replaced, on average, every month to ensure consistent availability of treated cotton.
Erika Machtinger, associate professor of entomology in the College of Agricultural Sciences and co-author on the study, said she hopes the findings will give homeowners the confidence to participate in tick management around their homes and yards.
"Tick tubes are one of the few options for tick management a homeowner can use by themselves without hiring a certified pesticide applicator," Machtinger said. "Other measures can include removal of lawn debris and keeping grass mowed, as well as making sure to use personal protective behaviors like tick checks and permethrin-treated clothing."
Vector-borne disease cases continue to increase in the United States, the researchers said, with ticks being the most common culprit. In the Northeast and mid-Atlantic states, Lyme disease is the most frequently reported tick-borne condition, and it also represents the most frequently reported vector-borne disease nationwide, with more than 400,000 cases estimated per year.
Rodents - such as mice - are reservoirs for many of these tick-borne pathogens, including the bacteria that causes Lyme disease and the parasite that causes babesiosis, among others. There has been a lot of interest in strategies such as tick tubes that interrupt this transmission cycle, the researchers said, but the research on the efficacy of these strategies has had mixed results.
Machtinger said that previous studies were conducted in areas that have many chipmunks as well as white-footed mice. While both chipmunks and mice are good hosts for the pathogen that causes Lyme disease and can feed a lot of ticks, only mice use the cotton that is found in the tick tubes.
"We knew that here in central Pennsylvania, we don't have the same populations of chipmunks as other sites, such as those in suburban New England that were used in previous research," Machtinger said. "We thought it would be a good idea to take a look at how mice use these tubes in an area that has a different ecology."
For the current study, the researchers wanted to explore how the timing and seasonality of putting out tick tubes, as well as the distance between deployed tick tubes, affected how much cotton mice used from the tubes and whether this decreased tick burdens on mice.
Over two years, the team deployed tick tubes at five forested sites in central Pennsylvania at different times of year, with researchers setting out tubes in separate areas beginning in the spring, summer or fall. They then checked the tubes every two weeks to measure how much cotton was removed and assessed tick burdens on mice every two months.
In addition to their other findings, the researchers found that cotton use from tick tubes was highest in late September and October, coinciding with peak mouse populations and increased demand for nesting materials. Machtinger said that consistent deployment and replacement of tick tubes throughout the year, or targeting cooler months with high cotton use, appeared to be more important for effectiveness than the specific season of initial deployment.
The researchers noted that while their study found that tick tubes reduce the number of ticks on mice, ticks also feed on many other animals. Therefore, there is a possibility that the tick numbers in the environment will not be affected as dramatically as those on the mice.
"However, many other wildlife species do not carry the pathogens that cause Lyme disease and other tick-borne diseases, whereas mice are very good hosts for those pathogens and for ticks," Machtinger said. "By killing ticks feeding on mice, those ticks will not have a chance to pass on infection, so we hope to see a reduction in ticks in the environment being infected with tick-borne pathogens."
Moving forward, Machtinger said the next step will be to develop a large-scale, multi-year evaluation of tick tubes that examines levels of ticks in the environment. The project is set to begin next summer.
Hannah Tiffin, University of Kentucky; Kylie Green, University of Georgia; and Edwin R Burgess IV, University of Florida, also co-authored the study. Machtinger also expressed gratitude for the members of the Veterinary Entomology Laboratory who worked on this project and others, as well as the Pennsylvania Game Commission for authorizing these studies in the game lands around State College.
Thermacell Repellents Inc. helped support this research.
