New environmental epidemiology approach sheds light on cattle's role in malaria transmission

A study led by researchers from the Barcelona Institute for Global Health (ISGlobal), the University of Navarra, the Kenya Medical Research Institute, and Virginia Tech, the Universities of Oxford, Bern and Harvard has mapped cattle distribution to investigate how their geographic proximity to human populations influences malaria transmission. The study, published in BMJ Global Health, is the first to apply an environmental epidemiology approach to assess whether livestock amplifies or reduces the risk of malaria transmission.

Role of cattle in malaria transmission

Scientists have spent decades developing strategies to control malaria vectors. One of the most debated questions concerns the role of cattle in malaria transmission, giving rise to two competing hypotheses: zooprophylaxis and zoopotentiation. The former suggests that cattle can act as an alternative blood source, diverting malaria-carrying mosquitoes away from humans. The latter proposes that livestock may increase mosquito populations and, consequently, enhance disease transmission. However, previous studies have typically treated livestock as a household-level resource, without considering its broader role as an environmental exposure across the wider landscape shared by multiple households.

Environmental epidemiology framework

The new study introduces a spatial approach based on cattle density within a defined area, treating livestock as an environmental variable rather than solely as a household characteristic. According to the study's first author, Almudena Sanz, a researcher at ISGlobal at the time of the study and currently at Virginia Tech, this approach captures spatial effects that extend beyond the household where the cattle are kept, "applying an environmental epidemiology framework for the first time, which may help explain why previous studies have produced conflicting results."

According to Carlos Chaccour, the study's principal investigator, also at ISGlobal at the time of the study and currently at the University of Navarra, this new methodology "could be used to evaluate livestock-based malaria control strategies and help resolve the long-standing debate between zooprophylaxis and zoopotentiation."

This study was carried out as part of the BOHEMIA project, funded by Unitaid, which conducted a trial in Mozambique and Kenya using a One Health approach. Ivermectin, a well-tolerated antiparasitic drug, was administered to both humans and livestock through mass drug administration campaigns to reduce the mosquito population and, consequently, malaria transmission.

Reference

Sanz Gutierrez A, Otuko R, Xie K, et al. Spatial exploration of the impact of cattle on risk of malarial infection using data from a cluster randomised trial. BMJ Global Health. 2026;0. doi:10.1136/bmjgh-2025-022607