Antibiotics Can Prevent Lyme Disease

B O S T O N, June 12 -- 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.