Borrelia burgdorferi is a species of Gram-negative bacteria. It can be found across much of North America and Europe. It is also the cause of Lyme disease which is a zoonotic, vector-borne disease transmitted by ticks.
The Lyme disease bacterium is spread through the bite of infected ticks. The blacklegged tick (or deer tick, Ixodes scapularis) spreads the disease in the northeastern, mid-Atlantic, and north-central United States, and the western blacklegged tick (Ixodes pacificus) spreads the disease on the Pacific Coast.