Study finds you probably can’t get Lyme disease from Utah ticks
Not all tick species are vector-competent, meaning not all possess the ability for the Lyme disease-causing bacterium to survive and multiply in their body and be transmitted to a human host. Ixodes pacificus is a vector-competent species, though all ticks of this species by USU scientists tested negative for Borrelia burgdorferi, the Lyme disease bacterium.
The map on the left shows the 157 sites where Utah State University researchers looked for ticks during a state survey. The map on the right shows where the researchers recovered the Western blacklegged ticks, the only tick species that can potentially carry Lyme disease in the region. The dark circles represent ticks recovered in the study and the gray dots represent historical collections.
Utah State University entomologist Jared Kunz uses a meter-square flannel drag net to collect ticks at a Utah study site. The USU team collected ticks from more than 150 sites in southern, central and northern Utah to update information about the state for U.S. Centers for Disease Control maps indicating the geographic distribution of ticks that bite humans. USU’s three-year, multi-county survey provided information that hadn’t been updated since the 1960s.
Ryan Davis, Utah State University 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 maps of the state’s tick distribution.
Back in the lab, Utah State University scientists, from left, Ricardo Ramirez, Scott Bernhardt, Laine Anderson and Ryan Davis, identify collected tick species and test for Lyme disease-causing bacteria. The team published findings in the ‘Journal of Medical Entomology.’
Not all tick species are vector-competent, meaning not all possess the ability for the Lyme disease-causing bacterium to survive and multiply in their body and be transmitted to a human host. Ixodes pacificus is a vector-competent species, though all ticks of this species by USU scientists tested negative for Borrelia burgdorferi, the Lyme disease bacterium.
Utahns have many reasons to despise ticks. They’re blood-sucking parasites, they’re a hassle to pluck off the skin and sometimes they’re bearers of awful maladies.
But new research offers some relief. It suggests that Utah ticks probably won’t give you Lyme disease.
Lyme disease comes from bacteria certain ticks carry and transmit to a host’s blood. It’s painful, it’s debilitating, it’s hard to diagnose, it’s hard to treat and it costs the U.S. healthcare system up to $1.3 billion a year.
An extensive survey conducted by Utah State University, however, revealed it’s hard to find ticks carrying the disease in the state. After covering nearly 100 miles from Logan to St. George over three seasons, dragging square-meter-sized flannel nets, the researches caught only 350 ticks total, showing there aren’t many ticks in Utah, period.
“We knew numbers couldn’t be all that high. If they were higher, people would talk about ticks more,” Bernhardt said. “I’ve done lots of outdoor activities and I’ve never had a tick on me. The only time I’ve had a tick is when I’ve gone out to try to collect them.”
That’s partly because Utah is hot and dry, and partly because there aren’t enough animal hosts for the ticks to feed on, like deer and rodents.
“If you go to the Northeast where Lyme disease is a real issue, you can walk a football field and collect as many ticks as we did in our entire study,” Bernhardt said. “The habitat is not present here. We do have ticks, but not in that type of concentration.”
Among the collected specimens, only 119 were western black-legged ticks, the only species that carry Lyme disease bacteria. And none of those ticks had the bacteria. Bernhardt said he wasn’t too surprised. There hasn’t been a documented case confirming that Lyme disease came from a Utah tick. But that’s not to say Utah’s completely in the clear.
“We didn’t find it, but that’s not to say it doesn’t exist. If it does, it’s very rare,” Bernhardt said. “It’s not unusual to see Lyme disease-positive ticks. But if we saw a lot in Utah, I’d expect for us to see more human cases than what we’re seeing.”
Ryan Davis with the Utah State University Extension had the idea to conduct the tick survey after a spout of Lyme disease outbreaks in Lehi. Those cases were later determined to have come from out-of-state ticks, but Davis also realized a statewide tick survey hasn’t been conducted in almost 50 years.
The surveys provide information the U.S. Centers for Disease Control use to map where ticks can bite and potentially infect humans in Utah. Davis, Bernhardt and two other researchers worked on the overdue, updated survey.
“Now mind you … we did not look at the entire state,” Bernhardt said. “It’s not feasible. We went where the majority of human population is located.”
Geography was the tick survey’s major limitation, but all the recovered western black-legged ticks with the potential to carry Lyme disease came from the St. George area and southwest of Provo.
Findings from the survey are published in the Journal of Medical Entomology.
