James Gathany; William Nicholson
The blacklegged ticks, I. pacificus, (depicted here), and I. scapularis, are known vectors for the zoonotic spirochetal bacteria Borrelia burgdorferi, which is the pathogenic bacteria responsible for causing Lyme disease. The ticks, inoculated with the bacterium when they bite infected mice, squirrels and other small animals, subsequently pass the pathogens to their human victims when they obtain a blood meal.B. burgdorferi bacteria can infect several parts of the body, producing different symptoms at different times. Not all patients with Lyme disease will have all symptoms, and many of the symptoms can occur with other diseases as well. If you believe you may have Lyme disease, it is important that you consult your health care provider for proper diagnosis.
The first sign of infection is usually a circular rash called “erythema migrans”, or EM. This rash occurs in approximately 70-80% of infected persons and begins at the site of a tick bite after a delay of 3-30 days. A distinctive feature of the rash is that it gradually expands over a period of several days, reaching up to 12 inches (30 cm) across. The center of the rash may clear as it enlarges, resulting in a bull’s-eye appearance. It may be warm but is not usually painful. Some patients develop additional EM lesions in other areas of the body after several days. Patients also experience symptoms of fatigue, chills, fever, headache, and muscle and joint aches, and swollen lymph nodes. In some cases, these may be the only symptoms of infection.