The drug, ivermectin, has been used in Africa for more than 15 years to treat… (James Gathany / Getty Images )
Researchers have hit upon a potential new tool to fight the spread of malaria — a drug commonly used to treat head lice and heartworm.
The Colorado State University scientists made the discovery while in Senegal during malaria season in August 2008 and August 2009.
The drug, ivermectin, has been used in Africa for more than 15 years to treat river blindness, a parasitic disease that often leaves its victims blind and is common in the same regions where malaria is contracted. With the assistance of the Senegalese Ministry of Health, the team traveled to three villages where people were receiving ivermectin and collected mosquitoes from inside huts before and two weeks after they had been treated with a single dose of the drug.
The scientists reported in the July issue of the American Journal of Tropical Medicine and Hygiene that the number of malaria-carrying mosquitoes fell by 80% two weeks after the residents had received ivermectin. In untreated villages, the percentage of malaria-laden mosquitoes jumped more than twofold during that same period.
Ivermectin paralyzes mosquitoes if they feed from a person who has been treated with the medication, killing the bloodsuckers before they can infect their next victim. As long as it's in the bloodstream, the drug acts as a 24/7 insecticide that targets mosquitoes that manage to bite.
"There is reason for cautious optimism," commented David Sullivan, a microbiologist at the Johns Hopkins Bloomberg School of Public Health who was not involved in the study. However, he added that the results will need to be repeated to confirm that the drug is an effective tool to control malaria, which kills approximately 1 million people each year, many of them children.
Ivermectin is a particularly attractive anti-malaria strategy because much of the infrastructure to get the drug to affected areas is already in place, experts said.
One complication is that it is typically not given to children younger than 5, which might give mosquitoes "a refugee population in which to hide," said Tom Unnasch, a microbiologist at the University of South Florida who also was not involved in the study.
The study's lead author, Brian Foy, a microbiologist at Colorado State University, said he and his team are seeking funding to study whether monthly administration of the drug could have longer-term effects and to show that cases of malaria — not just numbers of disease-carrying mosquitoes — decline with the treatment.
"We need bigger and better studies," he said.