Ticked Off: USU Biologists Seek Lyme Disease-Carrying Ticks in Utah
Ryan Davis, USU Extension arthropod diagnostician, suits up in protective gear for 'tick dragging,' a tick collection technique using a flannel drag net. He and USU colleagues completed a survey to update CDC maps of the state’s tick distribution.
The bad news is Lyme disease can be a debilitating, hard-to-diagnose and hard-to-treat illness. The good news is your likelihood of contracting the bacterial infection from ticks in Utah is low.
Those are findings of Utah State University scientists, who conducted an exhaustive three-year, multi-county tick survey at the request of the Utah Department of Health and Utah Bureau of Epidemiology. USU Extension Utah Pests arthropod diagnostician Ryan Davis and entomologist Ricardo Ramirez, along with USU undergraduate Laine Anderson and epidemiologist Scott Bernhardt, assistant professor in USU’s Department of Biology, published research results in the August 17, 2015, early online edition of the Journal of Medical Entomology.
The team’s efforts, funded by USU’s Extension Grants Program, provide long-overdue, much-needed information about Utah for U.S. Centers for Disease Control maps indicating the geographic distribution of ticks that bite humans. Tick-borne diseases, including Lyme disease, are the most commonly reported vector-borne diseases in the United States. A 2015 study by the Johns Hopkins Bloomberg School of Public Health estimates Lyme disease costs the health care system in the United States between $712 million and $1.3 billion each year.
“Tracking vector-borne disease is challenging,” says Bernhardt, a faculty member in the USU Department of Biology’s Public Health program. “In the case of tick-borne diseases, we have to carefully study the population distribution and abundance of the vector — in this case, ticks. In addition, we needed to survey for specific tick species capable of carrying and transmitting Borrelia burgdorferi, the Lyme disease-causing bacterium, as well as the presence of the bacterium itself.”
The USU study was prompted by a cluster of potential Lyme disease cases reported in Lehi, Utah, in 2010. Though Lyme disease was ruled out as the cause of most of the cases and the few positive cases appear to have been contracted out of state, the scientists, in partnership with the state of Utah and the CDC, set out to carefully survey ticks throughout the state and update maps not revised since the 1960s.
A first step in the study was gathering ticks from more than 150 sites of varied vegetation and terrain in southern, central and northern Utah. Over three field seasons, the researchers covered more than 90 miles on foot manually collecting nearly 350 of the tiny, six-legged arachnids using square-meter-sized flannel drag nets.
“It was a physically demanding undertaking,” Davis says, “But a necessary endeavor to collect accurate survey results.”
Though very similar in appearance, not every tick was of the same species. And determining the species of every single tick was crucial for the survey.
“Not every species of tick is vector-competent — that is, not all tick species possess the ability for Borrelia burgdorferi to survive and multiply in the tick and be transmitted to a new human host,” Bernhardt says. “So, all collected ticks were individually stored in vials and transported back to our lab in Logan for identification.”
The researchers meticulously photographed each tick, examined each critter under a microscope and identified four different species. Of the ticks collected, the team found 119 of the Ixodes pacificus species, the sole Lyme bacterium carrier of the survey. Undergrad Anderson performed DNA tests on each of the potential carriers and found no Borrelia burgdorferi.
“This is good news for Utahns,” Davis says. “However, our survey doesn’t state that borrelial-infected, vector-competent ticks don’t exist in Utah.”
The researchers caution that, under the right habitat and climatic conditions, Lyme disease-carrying ticks could proliferate in the Beehive state.
“As climate changes and the state’s population grows and more people recreate in tick-infested areas, it’s important to continue to monitor for these tick vectors,” he says.
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Contact: Scott Bernhardt, 435-797-3721, scott.bernhardt@usu.edu
Writer: Mary-Ann Muffoletto, 435-797-3517, maryann.muffoletto@usu.edu
In the lab, USU scientists, from left, Ricardo Ramirez, Scott Bernhardt, Laine Anderson and Ryan Davis, identify collected ticks' species and test for Lyme disease-causing bacteria. The team published findings in the 'Journal of Medical Entomology.’
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