Dear Doctors column, April 30, 2007

Take Precautions Against Lyme Disease

Question:

How can I protect against Lyme disease?

Answer:

Lyme disease, named after the town of Lyme, Connecticut, where it was first described in 1977, is caused by a type of bacteria called a spirochete that is transmitted to humans by a tick bite. The type tick that carries the organism is usually the deer, or black-legged tick, a small tick about the size of a sesame seed. These ticks feed not only on deer, but also on certain species of mice. In California, Lyme ticks also live on wood rats and other mammals, as well as some birds and lizards. Because of its small size, up to three-fourths of people with Lyme disease do not remember being bitten by a tick.

The number of reported cases of Lyme disease, as well as the number of geographic areas in which it is found, have been increasing. According to the May 7, 2004 Morbidity and Mortality Weekly Report, the number of Lyme disease cases in the country, increased by 40% from 2001 to 2002. Lyme disease has been reported in nearly all states in the United States, although more than 95% of all reported cases are concentrated in the coastal Northeast, mid-Atlantic states, Wisconsin and Minnesota, and northern California. In the United States, about 23,000 cases are reported each year. Lyme disease also is found in Asia and Europe.

The symptoms of Lyme disease, which can be difficult to diagnose, are usually divided into early, intermediate, and late symptoms. Within a few days after a tick bite that transmits the spirochete to the person's blood stream, a distinctive rash sometimes develops, characterized by a red area around the bite that enlarges and develops the appearance of a bull's eye target, followed by flu-like symptoms and fatigue. The symptoms of late Lyme disease may not appear until weeks, months, or even years after a tick bite. If untreated, patients may develop arthritis, neurological symptoms, and other serious problems. However, once the disease is diagnosed, it can be successfully treated with antibiotics.

There is a blood test for the disease. However, the blood test may not become positive until a month after initial infection. Also, if people with early Lyme disease take antibiotics, they may never have a positive test. The blood test is almost always positive in people who have been infected for more than 4 weeks and have not taken antibiotics.

The Lyme vaccine has been taken off the market. Not enough people wanted it, and it was complicated to administer (three shots), did not confer 100% immunity, and had side effects. Other vaccines are in the research stage.

To decrease the chance of being bitten by a tick:

• Avoid wooded, brush, and grassy areas, especially in May, June, and July.
• Wear light-colored clothing so ticks can be seen more easily.
• Wear long pants and long-sleeved shirts.
• Wear shoes covering the entire foot.
• Tuck pant legs into socks or shoes and shirt into pants.
• Wear a hat for extra protection.
• Spray insect repellent containing DEET on clothes and exposed skin (avoid the eyes), or treat clothes with permethrin that kills ticks on contact.
• Walk in the center of trails to avoid brush and grass.
• After being outdoors, remove clothing and wash and dry it at high temperatures.
• Do a careful body check for ticks, which require about 36 hours on the skin to transmit infection. To remove a tick, use tweezers and grasp the tick close to the skin. Pull straight back and avoid crushing the tick's body. You can save the tick in a small bottle of alcohol, in case you want to identify it later.
• Deer ticks can feed on dogs, which can catch Lyme disease and also bring infected ticks into your home. Check your dog when you get home.

For additional information about Lyme disease, talk with your doctor, health-care professional, or local health department, or contact the Arthritis Foundation, the American Lyme Disease Foundation, or  the Centers for Disease Control and Prevention.