A simple, inexpensive and surprisingly powerful combination of treatments all but wiped out malaria in a group of H.I.V.-positive children in a study in Uganda, scientists are reporting.
The combination — taking one inexpensive antibiotic pill each day and sleeping under an insecticide-treated mosquito net — reduced the incidence of malaria by 97 percent compared with a control group, Dr. Anne Gasasira, an AIDS researcher at Makerere University in Kampala, Uganda, said at a medical conference here on Wednesday.
She said the findings had already changed medical practice there. But scientists said they had not yet determined whether the treatment would be as effective in H.I.V.-negative children with malaria.
The antibiotic is known as cotrimoxazole, which is sold in the United States as Bactrim and Septra. It is used to prevent infections that are common complications of AIDS. The drug also has known benefits against the parasite that causes malaria.
"The findings were shockingly dramatic," said Dr. Elaine Abrams, a professor of pediatrics and epidemiology at Columbia University. Dr. Abrams was not connected with the Uganda study and moderated the session where the findings were reported, at the 14th Conference on Retroviruses and Opportunistic Infections.
Dr. Abrams and other experts said the findings had implications for better controlling malaria in Africa. Malaria is the leading cause of illness and death among children under 5 in Uganda, Dr. Gasasira said.
Although the World Health Organization does not recommend the combination, the United Nations agency does recommend each measure separately — cotrimoxazole for H.I.V. in Africa and bed nets to prevent malaria in infected areas.
Generic forms of cotrimoxazole cost less than $10 per patient each year in Uganda and the bed nets about $5, Dr. Gasasira said in an interview.
Because there are known interactions involving AIDS, malaria and other diseases, researchers have broadened their studies in Africa to find better ways to treat and prevent them.
The findings also extend to an earlier study that found a reduced frequency of malaria among H.I.V.-infected adults in Uganda who took the antibiotic and slept under bed nets. Dr. Jonathan Mermin of the Centers for Disease Control and Prevention in Atlanta led the adult study, which was published in The Lancet last year. But Dr. Gasasira said that because the adult and pediatric studies used different methodologies, the findings could not be directly compared.
Her study found that among 561 healthy children who were assumed not to be H.I.V.-infected and who did not take the antibiotic and sleep under bed nets, there were 356 episodes of malaria. This compared with four episodes among 300 children who were known to be H.I.V.-infected.
The 97 percent reduction was calculated by including other factors like the time they were under observation in the study that began in October 2005. The data were measured as of last August, but the study is continuing to determine if the findings hold up over a longer period. Additional studies are planned.
The infected children also received antiretroviral therapy, Dr. Gasasira said. Her team included researchers from the University of California at San Francisco and was paid for by the National Institute of Allergy and Infectious Diseases in Bethesda, Md.
The study came up with another important finding on the relationship between fever and malaria. Only 4 percent of fevers were from malaria among children who received the combination therapy in the study.
In the past, doctors assumed that a child who came to a clinic for fever in Uganda had malaria until it was proved otherwise. But because malaria was far less common among the participants who received the combination therapy, Dr. Gasasira said, doctors now assume that any fever in a young child must be investigated for a cause other than malaria.
Dr. Abrams, the Columbia expert, said in an interview that the Uganda findings had additional implications for treating H.I.V.-infected children in malarious areas. Because pediatricians are concerned that prolonged use of cotrimoxazole could lead to resistant malaria, they often stop the drug among AIDS patients when tests show significant improvement in the health of their immune system after antiretroviral therapy.
"This data will make us reconsider whether to stop cotrimoxazole" in such circumstances, she said.