Managing insecticide resistance in malaria vectors in Africa: case studies from Cameroon, Côte d’Ivoire and Tanzania

Authors: Raymond N Tabue, Constant GN Gbalegba, Charles D Mwalimu, Patrick K Tungu, Behi K Fodjo, Emmanuel Elanga-Ndille, Benjamin Menze, Jacklin Mosha, Rosine Z Wolie, Sian E Clarke, Jo Lines, Tarekegn A Abeku

While Cameroon, Côte d’Ivoire and Tanzania have insecticide resistance management plans in place to address the emergence and spread of insecticide resistance among malaria vectors, this study identifies the implementation gaps that are threatening their effectiveness.

Background
Malaria remains a significant public health challenge in sub-Saharan Africa (SSA), where vector control strategies, particularly insecticide-treated nets (ITNs) and indoor residual spraying (IRS), have played a critical role in reducing transmission. However, the emergence and spread of insecticide resistance among malaria vectors threatens to undermine these gains. In response, many countries in the region have developed national insecticide resistance management (IRM) plans. This study evaluates the adequacy and implementation of these plans in Cameroon, Côte d’Ivoire and mainland Tanzania, aiming to identify key challenges and best practices, and to develop actionable recommendations applicable to these and other countries with similar contexts.

Methods
A mixed-methods approach was employed, incorporating document reviews, epidemiological and entomological data analysis, and discussions with stakeholders and experts in 2023. The evaluation focused on the alignment of national IRM plans with national malaria control strategies, their operational effectiveness, and the ability to guide effective monitoring and management of insecticide resistance. The assessment was conducted before changes in the global aid funding landscape.

Results
Each country has developed a five-year IRM plan; however, the plans for Côte d’Ivoire and mainland Tanzania were found to be outdated. While the plans align well with national malaria strategies and international guidelines, implementation has been hindered by inadequate domestic funding and heavy reliance on external donors. Sentinel site coverage for resistance monitoring remains limited, though ITN campaigns have increasingly adopted targeted approaches using varied net types based on local data. IRS is sparsely deployed, but where it is used, rotation of insecticides with differing modes of action is practiced. Despite existing strengths, such as subnational tailoring of interventions, major challenges persist, including inactive monitoring sites and limited data availability due to financial and logistical constraints. The assessment identified important recommended actions, including increased mobilisation of domestic financing of resistance monitoring and management to offset shortfalls in external funding, updating of national IRM plans regularly by realistically aligning with available resources, and improved tailoring of effective vector control through high-quality and localised resistance and malaria risk data.

Conclusion
Insecticide resistance remains a significant threat to malaria control efforts across sub-Saharan Africa. Robust, adaptable IRM plans are essential to address this challenge. Case studies from Cameroon, Côte d’Ivoire, and mainland Tanzania reveal that such policy plans exist but implementation gaps, largely driven by funding shortages (a challenge that has increased since the study was completed), undermine the effectiveness of existing strategies. Strengthening domestic resource mobilisation, enhancing multisectoral coordination, and investing in systematic entomological surveillance are critical to ensure evidence-based, sustainable vector control programmes.

Citation: Malaria Journal, 2025; 24: 375.