Evaluating the Impacts of Piperonyl Butoxide-Treated Ceiling Nets on Malaria Risk Among High-Risk Populations with Limited Access to Conventional LLINs in Homa Bay Country, Kenya: Study Protocol for a Household Randomized Control Trial

Introduction: Progress in reducing the global malaria burden has stalled since 2015, with increases in malaria incidence and mortality reported in many African countries after 2020. In 2021, the WHO issued a conditional recommendation for house screening as a complementary intervention, but evidence gaps remain, particularly regarding its effectiveness in combination with or as an alternative to LLINs. This trial aims to evaluate the protective efficacy of PBO-ceiling nets, a novel house screening tool covering ceilings, among high-risk households in Kenya with poor use of LLINs. Methods: In Homa Bay County, Kenya, 500 households will be randomized into three arms: (1) receiving PBO-ceiling nets, (2) receiving piperonyl butoxide-pyrethroid long-lasting insecticidal nets (PBO-LLINs) at a ratio of one net per two household members, and (3) receiving both PBO-ceiling nets and PBO-LLINs. Target households will be selected using covariate-constrained randomization. The primary outcome is the prevalence of Plasmodium infections by PCR among all age groups at 24 months post-intervention. Secondary outcomes include entomological indicators, such as the density of primary malaria vectors sampled using CDC light traps. Discussion: This trial addresses key evidence gaps related to housing modifications for malaria prevention by evaluating the effectiveness of PBO-ceiling nets among high-risk populations with limited access to conventional LLINs. Although household-level randomization may limit the ability to capture potential spillover effects and introduce challenges such as open-label and observer biases, several measures have been incorporated to mitigate these risks, including frequent adherence reminders and blinding of laboratory and data analysis staff. Despite these limitations, the study is expected to generate important epidemiological and entomological data that will contribute to the evidence base for novel vector control strategies in malaria-endemic regions. Trial registration: PACTR202506499755138. Registered on June 20, 2025.