Lyme Disease-Carrying Ticks Now Found in Nearly Half of US Counties

Ticks carrying Lyme disease can now be found in nearly half of all U.S. counties, the CDC found in a new study.

"It’s important for people to be aware that there may be ticks in areas where they haven’t seen them previously so that they can take steps to help protect themselves and their families," lead study author Rebecca Eisen, a research biologist at the Centers for Disease Control and Prevention, told Reuters.

Since 1998, the blacklegged tick that may carry the bacteria responsible for Lyme disease has gone from living in 30 percent of U.S. counties to living in 45 percent of U.S. counties.

That means the ticks can now be found in 35 states, primarily concentrated in the northeast. The ticks appear to be moving west and south, however.

"Warmer temperatures, increases in rainfall, and milder winters can favor tick survival," said Dr. Bobbi Pritt, director of clinical parasitology at the Mayo Clinic in Rochester, Minnesota. "These factors can also favor survival and expansion of the mammals and birds that the ticks feed on."

Typically, both species of ticks that may carry the disease — deer ticks and the western blacklegged tick — are found in wooded and grassy areas. The ticks are thought to carry bacteria called Borrelia burgdorferi, which can cause fever, headache, and fatigue. Symptoms are often confused with flu symptoms, however some tick bites result in a so-called "bull's eye" rash.

Left untreated, Lyme disease can cause cognitive problems, joint and muscle pain, and mood disorders. If caught early enough, Lyme disease can be treated with antibiotics.

Overall, the number of reported Lyme cases has more than tripled since the late 1990s.

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