The Lyme bacteria seen in North America is called Borrelia burdorferi. Borrelia is the genus and burdorferi is the species. It is a small spiral shaped bacteria which has the abitlity to morph into a cystic form, which is spore like, and an L-form or spheroblast, which is intracellular (lives inside cells). It is carried by ticks of the Ixodes genus. The organism resides in mammals like deer and white footed mice. These are called the reservoir. The vehicle, tick in this case, which transmits the infection from the reservoir hosts to the human hosts is called a vector. Since it a bacteria which causes disease it is called pathogenic. Many other species of bacteria do not cause disease in humans. The spirochete responsible for Lyme disease has been around for thousands of years, but Lyme disease is considered a new and emerging illness. In the 1970s a group of children with what looked like an epidemic of juvenile rheumatoid arthritis were studied by doctors called epidemiologists along with other experts. It was determined that the cause was a vector borne illness. The bacteria was not identified until 1982 when Dr. Burderferi first saw the spirochete under the microscope. This initial outbreak occurred in Lyme Connecticut, hence the name. At first Lyme was associated with arthritis and its characteristic rash. Over time there was an increased understanding of its diverse clinical manifestations and it was seen as a multi system disease. Since its discovery in the 1980s much work has been done to study the basic science of this microorganism. Much has been learned about its structure, life cycle and biological features. Thousands of studies have been published in major medical journals over the last 30 years. Much of the science indicates that it is hard to diagnose and is resistant to eradication with antibiotics. There have only been a few clinical studies which address the effects of long term antibiotics on persistent Lyme symptoms. The most recent studies support the use of long term antibiotics.
Co-infections such as Ehrlychia, Babesia and Bartonella are even newer than Lyme. The importance of these infections and the need to treat them aggressively remains an area of much debate.
The tick vectors, Ixodes, are frequently called deer ticks. This is a bit misleading. Adult ticks are frequently found on deer but most human infections are caused by immature forms of the tick called nymphs. The tick itself has a two year life cycle. Larval forms are the size of a dot; nymph forms are the size of a poppy seed and adult forms which are visible, but still very small, may all transmit Lyme disease. It is generally believed that the tick must be in contact with the skin for 48 hours to transmit the infection. But this too is open for debate. In general, the tick bites are not seen. When they are observed it may not be possible to accurately gauge how long the tick was on the skin. For every tick that is seen they may be many more which go unobserved.