Lyme disease, the most common ahropod-borne disease in the United States, is primarily caused by the bacterium Borrelia burgdorferi. It is a spirochete, helically shaped, motile. Lyme disease is characterized by three clinical stages. The first stage is characterized by erythema chronicum migrans (ECM), an erythematous eruption at the location of the bite. The second stage occurs when the disease disseminates, producing ahritis, and cardiac manifestations. The third stage, the last and infectious stage, is characterized by ocular and joint findings. Borrelia parkeri cause relapsing fevers. Epidemic or louse-borne relapsing fever is caused by Borrelia recurrentis. Tick-borne relapsing fever is caused by Borrelia hermsii.