Deer Ticks Positive for Lyme Disease in Chicago

In an effort to minimize risk for acquiring tickborne diseases, the Cook County Department of Public Health (CCDPH) is issuing a warning about the discovery of deer ticks in forest preserve settings in southwest suburban Cook County.

Testing done last month found ticks positive for Borrelia burgdorferi, the bacterium that causes Lyme disease, a potentially serious illness that can affect humans and animals. “The deer tick is uncommon throughout most of suburban Cook County and the risk of contracting Lyme disease remains low,” said CCDPH chief operating officer, Stephen A. Martin, Jr., Ph.D, M.P.H. “But several diseases can be transmitted by tick bites, so people living in densely wooded subdivisions or spending time outdoors need to know how to avoid tick bites.”

The risk of exposure to ticks is greatest in wooded or brushy areas. To contract Lyme disease, a person must be bitten by a deer tick that is infected with the Lyme disease bacteria. Ticks are most likely to spread disease during the nymph stage, when they are very small and can feed without being detected.

“Although deer ticks are generally active during warm weather, ticks can be found in the winter if the ground temperature reaches 40 F,” said Dr. Martin. ”With the weather constantly changing in our area, it is possible to have warm enough days, even during the winter, that could activate the tick population.” Early symptoms of Lyme disease include a characteristic "bulls-eye" rash, consisting of an expanding reddened area, sometimes with a clear area in the middle, at the original site of the tick bite. The rash may expand in size to cover a very large area, or even appear in several places on other parts of the body. Other symptoms may occur and can include fever, swollen lymph nodes, headache, chills, and pain in the muscles or joints. If left untreated, Lyme disease infection can spread to the musculoskeletal system, heart, and the nervous system.