Excerpted from Reuters Health: (01/18/2016)
Ticks that can spread Lyme disease now live in almost half of U.S. counties, according to a new study from the Centers for Disease Control and Prevention.
Varieties of the blacklegged tick that may carry bacteria responsible for Lyme disease are present in 45 percent of counties nationwide, compared with just 30 percent in 1998, researchers found.
“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 CDC, said by email.
Lyme disease is a bacterial infection spread by the blacklegged tick, Ixodes scapularis, also known as deer ticks, and the western blacklegged tick, Ixodes pacificus. These ticks are typically found in wooded and grassy areas.
Bacteria called Borrelia burgdorferi cause Lyme disease. Common symptoms can include fever, headache, and fatigue, all of which can be easily confused with the flu. Some patients, but not all, develop a characteristic “bull’s eye” rash soon after the tick bite.
If caught early, Lyme disease can be treated with antibiotics. But untreated Lyme disease can lead to lasting cognitive problems, joint and muscle pain and mood disorders.
To assess changes in the tick population, researchers analyzed data reported by counties using the same surveillance methods from 1998.
They found deer ticks in 1,420 out of 3,110 counties in the continental U.S., or about 46 percent of counties, and found western blacklegged ticks in 111 counties, or about 4 percent. Combined, this is a 45 percent increase from 1998 when ticks were reported in 1,058 counties.
Deer ticks are now established in 842 counties across 35 states, compared with 396 counties in 32 states in 1998. These ticks used to be concentrated in northeastern states but have move west and south.
Western blacklegged ticks are now established in 95 counties across six states, up from 90 counties in 1998. These ticks remain concentrated in Pacific coast states.
Outside of the U.S., ticks carry the disease in forested areas of Asia, northwestern, central and eastern Europe, according to the World Health Organization.