Drug Shown Able to Kill Malaria-Carrier Mosquitoes

Clinical trial participant, who consented to being photographed, giving blood sample in clinical trial (Liverpool School of Tropical Medicine)

29 March 2018. A clinical trial in Kenya shows blood from people who take a current anti-parasite drug can kill mosquitoes carrying malaria, offering a potential new strategy for controlling this disease. Results of the study conducted by Liverpool School of Tropical Medicine in the U.K. appear in the 27 March issue of the journal Lancet Infectious Diseases (free subscription required).

Malaria, according to World Health Organization, affected 216 million people in 2016, which extracts heavy social and economic burdens in developing countries. In 2016, some 445,000 people died from malaria, of which 90 percent were in sub-Sahara Africa. Children under the age of 5 are particularly susceptible to the disease. The disease is caused by infections from the plasmodium parasite transmitted by mosquitoes. In humans, the parasite multiplies in the liver, then infects red blood cells. Symptoms, including headache, fever, and vomiting, occur 10 to 15 days following transmission from a mosquito bite.

A team led by Menno Smit, a physician as well as a doctoral candidate in malaria epidemiology, investigated use of ivermectin, a drug currently approved and given for parasite-borne diseases such as threadworm and river blindness that works by killing young, developing worms that infect individuals. Smit and colleagues from Liverpool and the Kenya Medical Research Institute tested a hypothesis that combining ivermectin with dihydroartemisinin-piperaquine, a therapy for malaria, could not only treat malaria in individuals, but also control mosquitoes that spread the disease to others.

The clinical trial recruited 141 adults with malaria but no further complications at a hospital in Kisumu in the western part of Kenya. Participants were randomly assigned to receive ivermectin in doses of 300 or 600 milligrams per day once a day for 3 days, along with the standard course of dihydroartemisinin-piperaquine, while a third group is given only dihydroartemisinin-piperaquine. After 7 days, participants gave blood samples, which were then fed to caged mosquitoes responsible for transmitting the malaria parasite in sub-Saharan Africa.

The results show blood from people taking ivermectin kills more mosquitoes than people not taking the drug. After 7 days following taking the samples, blood from people taking the 600 milligram dose of ivermectin killed 97 percent of the mosquitoes, while blood from the 300 milligram dose recipients killed 93 percent, and 41 percent from those not taking the drug. These effects decline somewhat over the next 14 days, but still remained higher for the blood taken from people receiving ivermectin. Somewhat more participants receiving ivermectin reported drug-related adverse effects at the higher dose (11%) that at the lower dose (4%).

The authors conclude that adding ivermectin to standard dihydroartemisinin-piperaquine, particularly at the 300 milligram dose, offers a promising new weapon against malaria. Smit also notes in a Liverpool statement, “We worked with colleagues from Imperial College London, who used our results in a mathematical model, which predicts that the addition of high dose ivermectin increases the impact on malaria reduction by potentially as much as 61 percent.”

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