Ivermectin mass treatment shows great promise in reducing malaria transmission

Ivermectin administered to the whole population significantly reduces malaria transmission, offering new hope in the fight against the disease. The BOHEMIA trial, the largest study on ivermectin for malaria to date, showed a 26% reduction in new malaria infection on top of existing bed nets, providing strong evidence of ivermectin's potential as a complementary tool in malaria control. The results of this project, coordinated by the Barcelona Institute for Global Health (ISGlobal) -an institution supported by the "la Caixa" Foundation- in collaboration with the Manhiça Health Research Centre (CISM) and the KEMRI-Wellcome Trust Research Programme, have been published in The New England Journal of Medicine. 

Malaria remains a global health challenge, with 263 million cases and 597,000 deaths reported in 2023. Current vector control methods, such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), have become less effective due to insecticide resistance and behavioral adaptations in mosquitoes to bite outdoors and during dusk or dawn, when people are not protected by these measures. This underscores the urgent need for innovative solutions to combat malaria.

Ivermectin for malaria: A novel strategy

Ivermectin, a drug traditionally used to treat neglected tropical diseases like onchocerciasis, which causes river blindness, and lymphatic filariasis, which causes elephantiasis, has been shown to reduce malaria transmission by killing the mosquitoes that feed on treated individuals. Given the rising resistance to conventional insecticides, ivermectin could offer an effective new approach to tackle malaria transmission, especially in regions where traditional methods have become less effective.

The Unitaid-funded BOHEMIA project (Broad One Health Endectocide-based Malaria Intervention in Africa) conducted two Mass Drug Administration (MDA) trials in the high-burden malaria regions: Kwale County (Kenya) and Mopeia district (Mozambique). The trials assessed the safety and efficacy of a single monthly dose of ivermectin (400 mcg/kg) given for three consecutive months at the start of the rainy season in reducing malaria transmission. In Kenya, the intervention targeted children aged 5–15, while in Mozambique it focused on children under five.

Malaria reduction in Kenya

In Kwale County, Kenya, children who received ivermectin experienced a 26% reduction in malaria infection incidence compared to those who received albendazole, the control drug used in the study. The trial involved over 20,000 participants and more than 56,000 treatments, demonstrating that ivermectin significantly reduced malaria infection rates-particularly among children living further from cluster borders or in areas where drug distribution was more efficient. Moreover, the safety profile of ivermectin was favourable, with no severe drug-related adverse events and only mild, transient side effects already seen with ivermectin in campaigns against neglected tropical diseases.

"We are thrilled with these results", says Carlos Chaccour, co-principal investigator of the BOHEMIA project and ISGlobal researcher at the time of the study. "Ivermectin has shown great promise in reducing malaria transmission and could complement existing control measures. With continued research, ivermectin MDA could become an effective tool for malaria control and even contribute to elimination efforts," Chaccour, who is now a researcher at the Navarra Centre for International Development at the University of Navarra, adds. 

"These results align with the World Health Organization's (WHO) criteria for new vector control tools", states Joseph Mwangangi, from the KEMRI-Wellcome Trust Research Programme.

The findings suggest that ivermectin MDA could be a valuable complementary strategy for malaria control, particularly in areas where mosquito resistance to insecticides is a growing concern."

Marta Maia, BOHEMIA's lead entomologist, University of Oxford

Lessons from the Mozambique trial

In contrast, the implementation of the Mozambique trial in the rural district of Mopeia faced severe disruptions due to Cyclone Gombe (2022) and a subsequent cholera outbreak, which significantly disrupted operations. "One of the most important lessons we learned from the trial in Mopeia is that strong community engagement is essential," states Francisco Saúte, director of the Manhiça Health Research Centre (CISM). "Building trust with local communities and fostering close collaboration with the Health Ministry, National Malaria Control Program, and local authorities was key to ensuring acceptance of the ivermectin MDA."

Expanding the impact beyond malaria

In addition to reducing malaria transmission, ivermectin MDA offers significant collateral benefits. The BOHEMIA team found an important reduction in the prevalence of skin infestations such as scabies and head lice in the ivermectin group in Mozambique, and the community reported a major reduction in bed bugs in Kenya. These effects are particularly valuable when ivermectin is integrated into existing delivery systems, maximising its impact on public health.

Shaping the future of malaria prevention

The study is part of a larger global effort to assess ivermectin's potential in malaria control. The findings have been reviewed by the WHO vector control advisory group, which concluded that the study had demonstrated impact and recommended further studies. Findings were also shared with national health authorities as they evaluate the potential inclusion of ivermectin in malaria control programmes.

"This research has the potential to shape the future of malaria prevention, particularly in endemic areas where existing tools are failing", concludes Regina Rabinovich, BOHEMIA PI and Director of ISGlobal's Malaria Elimination Initiative. "With its novel mechanism of action and proven safety profile, ivermectin could offer a new approach using a well-known, safe drug that can add to the effect of other mosquito control tools available today."