Colorado State University Researchers Discover Common Drug Kills Malaria-Carrying Mosquitoes

Note to Reporters: Broadcast quality video is available for download on the CSU News website at Video clips include interview questions and answers with Dr. Foy as well as B roll of the Foy lab. To download the video, visit In addition, a short video about the research is available at

Colorado State University researchers have discovered that a common and cheap medication used to fight roundworm and other parasites that plague people in Africa may offer an important strategy in the fight against malaria. The drug could prevent the transmission of malaria by killing mosquitoes, according to a CSU study published today in the American Journal of Tropical Medicine and Hygiene.

The drug, called ivermectin, appears to kill malaria-carrying mosquitoes that feed on people who are taking it. Researchers discovered a link when the rate of transmission of malaria fell among people taking the drug during a campaign to prevent river blindness. River blindness is caused by a roundworm called Onchocerca volvulus.

“The discovery of the multiple benefits of this drug in fighting parasites and mosquitoes carrying parasites is exciting,” said Brian Foy, senior author of the study and a vector biologist at CSU’s College of Veterinary Medicine and Biomedical Sciences. “We need innovative, new tools to fight malaria, and using ivermectin as a tool is especially exciting because it fights multiple diseases in the same community of people.”

Foy and a team of researchers developed their hypothesis that ivermectin may interrupt malaria transmission and then gathered and analyzed data for more than two years as part of the study. Foy worked closely with CSU colleagues Kevin Kobylinski, Massamba Sylla and Phillip Chapman. All four are researchers in the Department of Microbiology, Immunology and Pathology. The research also partnered with Dr. Moussa Dieng Sarr from the Ministry of Health and Preventative Medicine in the African country, Senegal.

In this study, researchers collected and examined samples of mosquitoes where people were taking the drug and compared them to samples in other villages. They found that mosquitoes carrying the deadliest strain of malaria in the villages where people were taking ivermectin dropped by 79 percent two weeks after the drug was administered, and in villages where people were not currently taking the drug, those numbers of mosquitoes increased by 246 percent.

While Foy notes that scientists need to better understand how dosages and timing of the doses may impact the use of the drug as a preventive strategy, he believes that ivermectin may reduce the incidence of malaria during epidemics or during seasons when transmission is most common. Malaria kills almost 800,000 people across the globe a year, with the majority of deaths being children in Africa.

Once more data on dosage amounts and timing is gathered, Foy hopes to eventually propose a small clinical trial in Africa.

There currently are few viable options for controlling malaria in Africa. Bed nets coated with insecticide are often used in the home, along with bug sprays, which helps during the evening hours, but there are no significant measures offering daytime, outdoor protection. Scientists are concerned that mosquitoes may be developing resistance to the insecticides used in these measures, so they are looking for additional tools to use in combination with current strategies.

Malaria is spread by mosquitoes carrying a parasite that causes the disease. This study focused on mosquitoes carrying Plasmodium falciparum, the most deadly malaria parasite in the world.

River blindness, the disease effectively and cheaply treated with ivermectin, affects about 18 million people a year. River blindness is spread by black flies that transmit roundworms into skin. The roundworms can migrate from the skin into infected people’s eyes, and about 270,000 people become blind from the disease each year. Ivermectin also is effective against parasitic worms that cause elephantiasis, a disease often transmitted by the malaria-transmitting mosquitoes. Hundreds of millions of doses are used in Africa to prevent heartworm, intestinal worms in animals, and to kill body and head lice and the mites that cause scabies. It also is used in the United States to treat head lice in children and also heartworm in pets.

In many areas of Africa, ivermectin is given to treat river blindness once or twice a year for free, and also at least annually in large public health programs to eliminate elephantiasis. For use in preventing malaria, it would likely have to be taken more frequently and during seasons when malaria is most likely to be transmitted.

The study is funded in part with grants from the U.S. National Institutes of Health and from the Bill & Melinda Gates Foundation’s Grand Challenges Explorations program, which rewards creativity in research.

A video about this research is available at