Avoid Lyme Disease this Summer

Lyme disease is a bacterial infection that is transmitted to humans via the bite of the deer tick. The deer tick and Lyme disease are found in most states in the U.S. Lyme disease is most common in New England, the Mid-Atlantic states (including Pennsylvania), Minnesota, Wisconsin and northern California. Deer ticks are found on deer and, particularly in the northeastern U.S., on rodents including the white-footed mouse. The biting ticks are active in mid-May, peaking in June and becoming dormant in July. Since the incubation period between receiving a tick bite and demonstrating symptoms is two to three weeks, most cases of Lyme disease present in June, July and August. Lyme disease is the most common disease carried by ticks in the United States.

There are three stages of Lyme disease. Stage 1 (early localized disease) is characterized by a particular skin rash–erythema migrans–which enlarges to up to 12 inches across and resembles a bull’s eye. This rash affects 70 to 80 percent of infected people. Fever, chills, fatigue, body aches and headache may accompany the rash and mimic a viral syndrome. In Stage 2 (early disseminated disease), patients may have several erythema migrans lesions. Weeks or months after infection, neurologic symptoms may appear, including Bell’s palsy (temporary paralysis of one side of the face) or meningitis. More subtle signs–such as memory loss, difficulty concentrating and sleep difficulty–may also develop. Less commonly, patients may have heart problems including an irregular heartbeat.

Stage 3 (late disease) may be characterized by arthritis, usually involving a large joint such as the knee. Some of these patients may suffer from subtle confusion. These symptoms may develop months to years after the initial tick bite and, if the initial stages of the disease have gone undiagnosed, may actually be the symptoms that bring a patient to medical attention.

Early Lyme disease can be diagnosed without lab tests, just by recognizing the characteristic erythema migrans rash. In fact, lab tests obtained early in the course of the illness may be negative if the body has not had time to develop the expected immune response. In contrast, by the time a patient has signs of early disseminated or late Lyme disease, the immune response will have occurred and lab tests for bacterial antibodies will be positive, making this a useful diagnostic test for Stage 2 and Stage 3 disease.

Oral antibiotics, most commonly doxycycline, are the usual treatment for early localized Lyme disease. This treatment usually lasts 14 to 21 days. For later disease, some patients will require 14 to 28 days of intravenous antibiotics. Although a patient may complete treatment in 2 to 3 weeks, he or she may continue to suffer symptoms for much longer.

Preventing Lyme disease is accomplished by following some basic guidelines. Avoid deer ticks. If you are going to be in an area where you might be bitten by a tick (that is, a wooded or grassy area in the geographic zones mentioned above), wear long pants and sleeves. Wear light colored fabrics so that a tick may be spotted more easily. Use insect repellants–preferably one with 10 to 30 percent DEET–on your skin and clothing. Keep grass trimmed short and don’t let big piles of leaves or brush build up in your yard. Check yourself, your children and your pets for ticks.

Remember that deer ticks may be smaller than the size of the head of a pin. If you find a tick, remove it carefully with tweezers, without squeezing or crushing the tick. Few people are bitten by deer ticks in winter months. Transmission of the bacteria to humans rarely occurs within 48 hours of attachment of the tick.

Dr. McMahon, a graduate of Yale University and the University of Pittsburgh School of Medicine, is board certified in Internal Medicine. She is a member of the American College of Physicians and the Allegheny County and Pennsylvania Medical Societies. She is in solo practice in the North Hills of Pittsburgh.