The arrival of warm weather this year means we have to start worrying a little bit about Lyme Disease. Most people are aware of the association between tick bites and Lyme disease, but few know exactly what Lyme disease is or what causes it.

Lyme Disease was named in the late 1970s when an outbreak of arthritis in children occurred around the town of Lyme, Connecticut. The actual disease has been described since the early 1900s.

Ticks are not the causative agent in the disease though they do carry the organism that does cause it - the spirochete Borrelia burgdorferi. Spirochetes are bacteria that have a spiral shape. Another common misconception is that any tick can spread B. burgdorferi infection, when in fact the organisms are carried only by Ixodes (deer) ticks. The accompanying photo shows a deer tick on a fingernail - they are very small.

Fortunately for our readers, Lyme disease is not common in central Indiana. It is mostly found in New England as well as Wisconsin and Minnesota. When a case does occur in Indiana, the news spreads rapidly, sometimes inciting panic. Most infections (85 percent) are seen in the spring and summer with the remainder in the fall.

The B. burgdorferi organism infects mainly field mice and white tailed deer during its various life stages. Humans are innocent bystanders when we wander into deer habitat. The ticks lie in wait on the tips of grasses and shrubs and crawl onto us as we brush by. They then crawl about until they find a nice tender spot where they attach and begin to feed.

The risk of contracting B. burgdorferi is very small until the tick has been attached and feeding for two to three days. Not everyone will develop clinically significant Lyme disease if they are infected.

Lyme Disease has three stages. The first two stages are termed "early infection," and the third is called "late infection." The signs and symptoms are quite different during each stage.

Stage 1 consists of signs near the point of attachment of the tick. A characteristic rash called erythema chronicum migrans (ECM) usually develops. The rash is red (erythema), lasts for a few weeks (chronicum) and tends to enlarge or migrate with time (migrans).

Stage 2 involves disseminated (away from the bite) signs and symptoms. This stage can involve virtually any tissue, but signs and symptoms are usually found in the joints, nervous system and heart. Two-thirds of people develop arthritis that can occur in various joints and may migrate between joints. Nerve weakness as well as numbness and tingling may occur in the nerves of the face and elsewhere. Infection of the heart can cause rhythm problems.

Step 3, or late infection, can present up to a year after the organism invades the body. Approximately ten percent of people develop chronic arthritis, usually of the knee. They can also develop infection of the brain and spinal cord. Severe chronic malaise and fatigue can also result.

Testing for Lyme disease is very controversial. There is no standardized antibody test and the tests also are frequently falsely positive or negative. The CDC recommends that anyone with a positive test have it confirmed with a more specific test called a western blot. People with neurologic symptoms may require a spinal tap to look for infection.

Treatment for Lyme disease is fairly straightforward. Most people are treated with the antibiotic doxycycline. The length of treatment varies based on the stage and extent of infection. Some people with severe involvement may require hospitalization. This is most common with heart problems.

Simple steps can be taken to limit your risk of contracting Lyme disease. Even though Lyme disease is rare in Indiana, you should consider covering up when you're in the woods. This includes wearing a long shirt and pants as well as a hat. You should do a full body check for ticks after you've been in the woods and apply insect repellent with at least 30 percent DEET when going outdoors.

Removal of ticks can be tricky. You need to get a fine pair of tweezers and grasp the tick's head as close to the skin surface as possible and pull slowly and gently until the tick lets go. You should place the tick in alcohol for identification if needed. If you can't remove the tick, call your doctor.

Dr. John Roberts is a Crawfordsville physician and one of the owners of The Paper. In addition to his weekly column, he writes a Daily Health Tip on page A1.