Lyme disease (named for the town of Lyme, Connecticut, where the disease was first identified in patients) is an infection caused by the bacteria Borrelia burgdorferi. This bacteria is a spirochete -- when you look at it under the microscope, it appears coil- or spiral-shaped. (The shape of the bacteria has little to do with its "relatives"; the best-known spirochete in medicine is Treponema pallidum, which causes syphilis. Other than the shape of the cells, there are no similarities between Treponema pallidum and Borrelia burgdorferi. Lyme disease is carried by ticks, especially Ixodes scapularis (Ixodes dammani) and Ixodes pacificus. People are infected after being bitten by a carrier tick.
Since Lyme disease is caused by a bacteria, in can be treated with antibiotics. The choice of antibiotics depends on the stage of the disease (early disease can be treated with oral antibiotics, but late stage disease may require IV antibiotics, especially if there is meningitis or if the nervous system is otherwise involved, or if a patient has recurrent arthritis. Antibiotics we use to treat Lyme disease include amoxicillin, cefuroxime, and doxycycline, as well as erythromycin (which some authorities think may not work as well). Lyme disease is much easier to treat if you start early; once you reach the late stages, the effects of Lyme disease may continue even after the bacteria is killed.
The US Food and Drug Administration approved a vaccine against Lyme disease in December, 1998. Like some commonly-used vaccines, including the hepatitis B vaccine, the Lyme disease vaccine was recombinant (it is made by gene splicing, rather than directly from the Borrelia bacteria). It was approved for use in patients age 15-70 (although many children 2-15 years old get Lyme disease, the vaccine was not tested completely for use with young children). The vaccine was given in 3 doses: the second was given 1 month after the first, while the third was given 1 year after the first dose. The most common side effects include swelling, soreness, and redness at the site of vaccine injection, as well as fever, chills, and muscle aches; these seem to happen most often in the first 1-2 days after the vaccine is given. Unfortunately, not many people wanted the vaccine, and it was removed from the market in 2002.
Even after three doses of vaccine, only about 78% of patients became effectively immune to Borrelia. (With two doses, the chance of being effectively immune is about 50%.) So, even if you had the vaccine, you still need to take precautions against ticks and tick bites.
If you are outdoors in a tick-infested area, be sure to wear long-sleeved shirts and long pants, both light-coloured. Wear socks and shoes, and tuck the cuffs of your pants into your socks. And you should spray your shirt, pants, and socks with a tick repellent, and apply tick repellent (such as DEET) to any exposed skin. After you come inside, take all of your clothes off and inspect all of your for ticks -- and do the same with your kids and your pets (except that you probably won't have to take off your pets' clothes).
If you find a tick on your skin, remove it -- but don't touch the tick when you remove it. You can use fine-pointed forceps or tweezers; some camping supply stores carry plastic gadgets that work well also.
If you do develop a red, circular or ring-shaped rash, even if you don't remember being bitten by a tick at that location, and even if you have been vaccinated, see your doctor as soon as possible. Lyme disease is much easier to treat if you start the treatment early.