What is Lyme Disease?

Lyme disease is an infection caused by Borrelia burgdorferi, a type of bacterium called a spirochete (pronounced spy-ro-keet) that is carried by deer ticks. An infected tick can transmit the spirochete to the humans and animals it bites. Untreated, the bacterium travels through the bloodstream, establishes itself in various body tissues, and can cause a number of symptoms, some of which are severe.

The disease manifests itself as a multi-system inflammatory disease that affects the skin in its early, localized stage, and spreads to the joints, nervous system and, to a lesser extent, other organ systems in its later, disseminated stages. If diagnosed and treated early with antibiotics, lyme diseaseis almost always readily cured. Generally, in its later stages can also be treated effectively, but because the rate of disease progression and individual response to treatment varies from one patient to the next, some patients may have symptoms that linger for months or even years following treatment. In rare instances, it causes permanent damage.

Although lyme disease is now the most common arthropod-borne illness in the U.S. (more than 150,000 cases have been reported to the Centers for Disease Control and Prevention [CDC] since 1982), its diagnosis and treatment can be challenging for clinicians due to its diverse manifestations and the limitations of currently available serological (blood) tests.

The prevalence of lyme disease in the northeast and upper mid-west is due to the presence of large numbers of the deer tick's preferred hosts - white-footed mice and deer - and their proximity to humans. White-footed mice serve as the principal "reservoirs of infection" on which many larval and nymphal (juvenile) ticks feed and become infected with the lyme disease spirochete. An infected tick can then transmit infection the next time it feeds on another host (e.g., an unsuspecting human).