Antibiotics Can Prevent Lyme Disease

B O S T O N, June 12, 2001 -- For the first time, doctors have shown that aquick dose of antibiotics can ward off Lyme disease after a tickbite, but they caution against overusing the treatment.

Some physicians already give antibiotics to people who arebitten by deer ticks, the bugs that spread Lyme disease. However,many experts oppose this, because there has been no clear evidencethe treatment actually prevents the disease, even thoughantibiotics can clear up Lyme disease once it occurs.

Now there is proof the approach works. A study conducted in NewYork's Westchester County, where Lyme disease is common, found thatjust two pills of doxycycline are highly effective if given withinthree days of a bite.

"Ours is the first study to show that Lyme disease can beprevented after a tick bite," said the study's chief author, Dr.Robert B. Nadelman of New York Medical College in Valhalla, N.Y.

The study, to be published in the July 12 issue of the NewEngland Journal of Medicine, was released on the journal's Web siteearly today because of its importance.

About 15,000 cases of Lyme disease are reported annually in theUnited States, mostly in the Northeast from Maine to Maryland; theMidwest in Wisconsin and Minnesota, and the West in northernCalifornia and Oregon.

Tick Bites Rarely Lead to Infection

While confirming the effectiveness of so-called prophylacticantibiotics, the study also shows that even in a Lyme-infestedarea, deer tick bites rarely result in infection. In fact, onlynymphal stage bugs filled with blood posed a risk.

The latest study involved 482 people who had removed an Ixodesscapularis tick — the deer tick — from their bodies within theprevious 72 hours and took it with them to the doctor foridentification. They were randomly given either a 200-milligramdose of doxycycline or dummy pills.

The antibiotic was 87 percent effective at preventing Lymedisease, even though the overall risk was low, just 3 percent amongthose getting the dummy pills. This means it would be necessary totreat about 40 people to prevent one case of Lyme disease.

Still, Nadelman said it may make sense to treat people if theyare bitten by a blood-filled nymphal stage deer tick in an areawhere Lyme disease is common.

Deer ticks go through three stages. Larval stage ticks have sixlegs, while nymphal and adult ticks have eight. An unfed nymphaltick is the size of a poppy seed and an adult the size of a sesameseed. Nymphal ticks exist in most places only from May throughJuly.

Lyme disease causes fatigue, fever and joint pain that canpersist for weeks, and some patients develop severe arthritis. Lymealso can badly damage the heart and nervous system if it goesuntreated by antibiotics.

Signs include rash and flulike symptoms. Daily tick checks,vaccinations and insect repellent are recommended as preventivemeasures.

The idea of giving antibiotics to tick bite victims even beforethey show signs of Lyme disease has long been controversial. Lastyear, the Infectious Diseases Society of America releasedguidelines saying this should not be done routinely.

"Guidelines are made to be revised and revisited," saidNadelman, who helped draw up last year's recommendations. However, he said doctors should use antibiotics judiciously,because the medicine can cause nausea, especially if taken on anempty stomach.

"The danger is whether it will be used in situations wherethere is a very low chance of someone having Lyme disease," saidDr. Alan Barbour of the University of California at Irvine.

"People hear about this and ask their doctor, and the doctor ismore likely than not to go along with their requests."

Barbour said doctors should be taught in medical school how toidentify deer ticks. Some confuse them with other creatures, suchas tiny spiders, lice and other more common kinds of ticks.

Most people who get Lyme disease can be cured with antibiotics,although occasionally people have lingering symptoms. Otherresearch in the journal from Dr. Mark S. Klempner of BostonUniversity School of Medicine found that prolonged antibiotictreatment is ineffective against this condition.