When Carlos Chaccour called Cassidy Rist in her early days at Virginia Tech, she nearly didn’t pick up—after all, why would a veterinarian in the U.S. care about a Spanish doctor’s idea to use a livestock drug against malaria? But that phone call sparked a collaboration that has now proven, with real-world data, that ivermectin can slash malaria infections by 26% in children along coastal Kenya. For Rist, an associate professor of population health sciences, the journey from skepticism to scientific validation underscores a powerful truth: human and animal health are inextricably linked.
Malaria still kills around 600,000 people each year, mostly children under five in sub-Saharan Africa. While bed nets and insecticide spraying have saved millions, progress has stalled as mosquitoes evolve—biting earlier in the evening, resting outdoors, and increasingly feeding on livestock like cattle and goats. These shifts allow them to survive traditional interventions and continue spreading the parasite. This so-called residual transmission means even well-protected communities remain vulnerable.
Enter ivermectin, a drug long used in veterinary medicine to kill parasites in animals and in humans to treat river blindness. Researchers discovered decades ago that when mosquitoes feed on blood containing ivermectin, they die before they can reproduce or transmit malaria. The drug doesn’t target the malaria parasite—it targets the mosquito. "It is a vector control tool," Rist explains. "It has nothing to do with the parasites that cause malaria. It's treating the vector."
The breakthrough came from the BOHEMIA trial, a large-scale study conducted in Kenya and Mozambique. In coastal Kenya, mass administration of ivermectin to entire communities—including both people and livestock—cut malaria infections in children by 26%. Using that data, Rist and her team conducted the first economic analysis of its kind, published in The Lancet Global Health, showing the strategy is not only effective but cost-effective when added to existing malaria controls. At a cost of less than $10 per disability-adjusted life year averted, it meets the World Health Organization’s threshold for high-value public health investment.
This isn’t a silver bullet, but it’s a powerful new tool—especially in areas where mosquitoes have outsmarted bed nets. For health ministries and global funders, the evidence is now clear: integrating ivermectin into malaria programs could close critical gaps in protection. As Rist’s journey shows, sometimes the most promising solutions come from unexpected places—even a phone call from a stranger with a seemingly wacky idea.