Government-Academic Partnership Gathers Tick Data

FIA crewmembers – such as the one shown here working his way through a blackberry thicket – often refer to November to February as tick season. Scientists collected ticks throughout the year, however, to include variation in tick species encounters. Photo by J.T. Vogt, USFS.

As an intern with the USDA Forest Service, I’ve had my fair share of run-ins with ticks. My first trip into the field took me deep into a relatively untamed forest. The other three interns tagging along were surprisingly serene about the bounty of insects and spiderwebs everywhere; I was constantly swatting away bugs and checking my socks and pants for ticks every few minutes.

While my aversion to bugs might be extreme, some caution is certainly a good idea. Ticks are present in relatively high concentrations during the summer, and they cause ailments such as Lyme disease, Rocky Mountain spotted fever, and Ehrlichiosis.

Scientists are well aware of this. In fact, a recent study by University of Tennessee Associate Professor of Entomology Rebecca Trout Fryxell and Forest Service biological scientist J.T. Vogt tackled the tick problem through surveillance.

They established a government-academic partnership for USDA field crews to self-monitor for ticks and for the University of Tennessee to identify the ticks. Their findings were published in the Journal of Medical Entomology.

The scientists saw a unique opportunity in the USDA Forest Service Forest Inventory and Analysis (FIA) program, in which trained crews gather an extensive list of data from around 130,000 plots in U.S. forests year-round.

“The idea is to have the FIA crews voluntarily self-examine for ticks on their clothing or on themselves,” explains Vogt. “We gave them vials to put ticks in, forceps to help remove them, and ethanol for preservation.” FIA crews working in thirteen southeastern states, including North Carolina, South Carolina, Tennessee, and Texas, submitted ticks for the study.

Multiple things about the FIA program made it a good candidate for surveillance. For one, the fact that the crews were trained in forest safety and data collection increased the likelihood that they would be astute and safe in their tick collecting. There were enough plots and crew visits to the plots to provide a large dataset.

FIA crews sample a portion of plots in every state each year. These data provide an annually update estimate of forest resources and conditions. Photo by J.T. Vogt, USFS.

In addition, the specific FIA plots the crews were sampling yielded detailed information about tick locations. “The crews checked for ticks when they began working on a plot and again when they exited it, so we could say with a reasonable degree of certainty where those ticks came from,” notes Vogt.

From July 2014 to November 2017, field crews collected 1,180 ticks. FIA headquarters sent the 198 vials of ticks to the Medical and Veterinary Entomology laboratory at the University of Tennessee, Knoxville, where Trout Fryxell’s research team identified their species, sex, and life stages.

The data were used to make presence maps, showing concentrations and locations of tick species based on the time of year. Descriptive statistics and encounter frequencies for certain life stages and species were also calculated.

The study establishes baseline data for tick encounters, which can provide a comparison for future years.

The study also has safety implications for those in the field. “This could give us a better idea of when to warn crews of higher tick concentrations,” Vogt says. “Dr. Trout Fryxell and I also think it’s reasonable to suspect that the crews that are heavily participating might be better off, since they’re checking themselves for ticks more.”

Trout Fryxell and Vogt are planning more research in the future. “We hope to improve on the spatial data by improving FIA crew volunteer rates,” says Vogt. “We’re missing data in Georgia, Mississippi, and Alabama, so we want to gather more data in those areas. As we move forward, we will also be doing landscape-level work to test the predictive value of FIA plot variables, such as forest type, for tick population densities.”

Read the full text of the article.

For more information, email J.T. Vogt at james.t.vogt@usda.gov.

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