Lyme Disease : Treatment, Vaccines

by Food and Drug Administration (FDA)

(Page 3 of 3)

Treatment

FDA has not approved any treatment specifically for Lyme disease, but doctors have prescribed commonly used antibiotics since about 1980.

"Well-known spirochetes, such as those that cause syphilis, are treated with amoxicillin. So physicians have extrapolated from that" and prescribe that drug to treat Lyme disease, says FDA's Albrecht.

For FDA to specifically approve a treatment, a large-scale, carefully controlled clinical trial would need to be submitted for review, she adds. But since useful drugs are already available, pharmaceutical manufacturers lack incentive to conduct such a trial.

Physicians most commonly prescribe oral doxycycline, amoxicillin or erythromycin. When oral antibiotics don't work or a patient has severe arthritis or neurological symptoms, the physician administers intravenous ceftriaxone or penicillin G. Doctors do not, however, prescribe antibiotics for tick bites if the patient has no Lyme disease symptoms. This is because not all ticks carry the spirochete — only 50 percent of ticks are infected in the most heavily infested areas.

One problem with using antibiotics to treat Lyme disease is that treatment can curtail the body's production of Lyme spirochete antibodies, which may make a person less resistant to repeat infection. "I know someone in Connecticut who got Lyme disease three times. Each time he got a rash, and treated it promptly, so no antibody response developed," says Schwan.

"Researchers are also interested in seeing if there are different strains of the spirochete. If there are, a person could develop immunity to one strain, then go somewhere else and encounter a different strain that isn't killed by the antibodies," he adds.

Vaccines

A vaccine is usually made from a killed microbe, or part of it, that signals the immune system to mount an attack. A Lyme disease vaccine containing a protein from the surface of the spirochete, called Osp A, is being evaluated in humans. It is currently being tested for efficacy in preventing Lyme disease in high-risk northeastern populations.

Vaccine test results in mice published in the June 1992 issue of the Proceedings of the National Academy of Sciences suggest that this particular vaccine has a double effect, protecting the mice while also stemming the spread of infection by ticks. In the experiment, uninfected mice were given the vaccine, then exposed to ticks carrying the Lyme bacteria. Vaccinated mice not only remained free of infection, but when the ticks bit them, the antibodies the mice had made after stimulation with the vaccine killed the spirochetes in the ticks too! Mice given a placebo instead of the vaccine became infected. The researchers, from Yale University and Harvard University School of Public Health, hope that Lyme disease may be controlled by adding the vaccine to the plants and water supplies that wild rodents consume. If rodents can no longer harbor the Lyme bacteria, then ticks cannot become infected and spread the disease.

Lyme disease may be disabling and painful. Fortunately, there is much you can do to prevent it (see œPrevention Tipsœ). But if you should pick up one of these tiny ticks and develop symptoms, be sure to see a doctor immediately. Caught early, Lyme disease can be halted if appropriately treated. n

Ricki Lewis, Ph.D., is a writer in Scotia, N.Y., and a biology textbook author. Prevention Tips

Health departments in areas where Lyme disease is prevalent offer these tips for preventing infection:

Wear protective clothing in woods and grasslands, and especially where these two areas meet. Wear long pants and long- sleeved shirts that are tight about the ankles and wrists; tuck pants into socks; wear shoes that cover the entire foot; and wear light-colored clothing so that the ticks can be easily seen.

Use repellent containing permethrin or DEET, but don't overdo it; children can have difficulty breathing from too much bug spray.

If you visit the woods, do tick checks when the day is done. Closely check hairy parts of the body, and examine pets, too. Ticks prefer rodents and deer, but will hop onto almost anything warm and furry, and while wild animals can harbor the spirochete without becoming ill, domestic animals do develop symptoms of Lyme disease. (A vaccine for dogs is available.)

If you find a tick, remove it with tweezers, being careful not to squeeze it. Apply antiseptic to the bite area. If possible, bury, burn or flush the tick. Researchers are currently looking at whether applying a topical antibiotic cream can stop the infection right after the bite.

About the Author

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