Insecticide Resistance Management in Malaria Vectors in Tanzania Mainland (2015-2024): A Scoping Review

Area of Science:

• Entomology
• Public Health
• Molecular Biology

Background:

• Insecticide resistance in malaria vectors poses a significant threat to the efficacy of key control tools like long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) in Tanzania.
• Understanding the evolutionary dynamics of insecticide resistance is critical for informing and adapting vector control policies in Tanzania.
• This review synthesizes existing evidence on resistance patterns, surveillance methods, and management strategies to guide programmatic decisions.

Purpose of the Study:

• To conduct a comprehensive review of insecticide resistance patterns, underlying mechanisms, and management strategies in Tanzanian malaria vectors between 2015 and 2024.
• To identify and highlight existing research and surveillance gaps in insecticide resistance management within Tanzania.
• To provide evidence-based recommendations for strengthening vector control programs.

Main Methods:

• A scoping review methodology was employed, adhering to the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) framework.
• Literature searches were performed across multiple scientific databases to identify relevant studies based on predefined eligibility criteria.
• Data extraction focused on resistance patterns, identified resistance mechanisms, surveillance approaches utilized, and implemented management strategies, followed by a synthesis of the findings.

Main Results:

• Pyrethroid resistance is consistently reported in Tanzanian malaria vectors, primarily driven by knockdown resistance (kdr) mutations and enhanced metabolic detoxification.
• Resistance to DDT is prevalent, while moderate resistance to carbamates is observed in approximately half of the studies. Organophosphate insecticides, such as pirimiphos-methyl, and newer agents like clothianidin and chlorfenapyr, remain effective with no resistance detected.
• Management strategies include the use of pyrethroid-PBO LLINs and integrated vector management, but inconsistencies in surveillance coverage and detailed mechanistic profiling were noted across different study sites.

Conclusions:

• Insecticide resistance, particularly to pyrethroids, is a widespread challenge for malaria vector control in Tanzania.
• Emerging insecticides and integrated management strategies offer potential solutions, but their effectiveness is currently limited by gaps in surveillance data and operational research.
• Enhancing research capacity, securing sustained funding, and fostering cross-sectoral collaboration are essential to support evidence-based insecticide resistance management and safeguard malaria control achievements.