BOSTON (Reuters) - Doctors trying to find a better treatment for the malaria-like infection known as babesiosis found that the double-drug combination of atovaquone and azithromycin is as effective as the standard treatment but causes fewer side effects.

Babesiosis is carried by ticks and is concentrated in southern portions of New York and New England, along with Wisconsin. Without treatment, it can persist for more than two years.

Doctors typically attack it with clindamycin and quinine, but those drugs frequently cause diarrhea and a ringing in the ears. The study published in Thursday's New England Journal of Medicine (news - web sites) was designed to determine whether the combination of atovaquone and azithromycin worked as well.

A team led by Dr. Peter Krause of the University of Connecticut School of Medicine found that the symptoms of babesiosis, which include fever and chills, disappeared after three months in 65 percent of the 40 people who were given atovaquone-azithromycin.

The figure was 73 percent for the 18 given clindamycin and quinine, the researchers said. The difference was not statistically significant.

However, there was a big difference in the rate of side effects. While only 15 percent of the volunteers in the atovaquone-azithromycin group experienced side effects, including rash and diarrhea, 72 percent of the people getting clindamycin and quinine developed problems such as diarrhea and hearing problems.

Krause and his colleagues said the atovaquone-azithromycin treatment ``is generally superior'' mainly because it ``is better tolerated by patients.''

It was not tested in people whose disease was life-threatening.

Atovaquone is sold under the brand name Mepron by Glaxo Wellcome Plc. Azithromycin is manufactured by Pfizer Inc., which markets it as Zithromax. Clindamycin and quinine are both made by several companies.

Babesiosis is an infectious disease caused by a parasitic single-celled microorganism. The disease is transmitted to people by the bites of ticks that have picked up the parasite from infected animals, such as rodents and horses. Cases also have been seen in Europe.

(From Reuters)