Borrelia burgdorferi is the species of spirochete bacteria responsible for Lyme Disease. It is transmitted by Ixodes ticks (also known as deer ticks) and was recognized by the mid 1930s and at that time was called tick-borne meningoencephalitis.
In the United States, Lyme disease was not recognized until the early 1970s, as an outbreak of childhood arthritis took place in the Lyme, CT area. This was investigated by Allen Steere, MD, and others from Yale. The acknowledgment that the patients in the United States had ECM led to the realization that Lyme arthritis was one manifestation of the same tick-borne condition known in Europe. After Willy Burgdorfer, MD, discovered a borrelial organism in Ixodes ticks, it was found in patients with clinical Lyme disease, substantiating it as the responsible agent. This led to the development of antibody tests for the disease. Several different strains of Borrelia are recognized, which explains why the clinical manifestations of Lyme disease are varied in the United States and Europe.
Here are some pictures of Borrelia burgdorferi that I found at lymephotos.com. Take a look at their site as they have many more pictures.
Here is another great image which details the structure and morphology of Borrelia burgdorferi.
