Long-Lasting Insecticidal Nets (LLINs) are the front line malaria vector control tool in sub-Saharan Africa (SSA), with most countries adopting universal coverage campaigns with free or subsidised nets. It is essential to understand the effective life of LLINs: that is the cost per year of protection that they provide. Public health policy makers may then use this information to select the most cost effective nets (rather than the cheapest that might not last very long), and estimate the correct timing of repeated distribution campaigns to ensure that maximal health gains are maintained. However, there is only limited knowledge from few countries of the effective life of LLINs under user conditions.
This study investigates LLIN effectiveness in eight districts of Tanzania, selected for their demographic, geographic and ecological representativeness of the country as a whole.
To determine the useful life of LLINs from 1) a retrospective survey of Olyset® nets distributed by the Tanzanian Government two-to-four years previously; and 2) a prospective study of three different LLIN products (Olyset®, Permanet®2.0 or Netprotect®) over three years using a nation-wide sampling framework across eight districts in Tanzania.
- Determine Attrition (net loss) of LLINs.
- Determine Biological efficacy of LLINs by assessing mosquito mortality through WHO-approved methods and new alternative methods (for validation of WHO methods).
- Determine Chemical residues in LLINs through High Performance Liquid Chromatography (HPLC).
- Determine physical Degradation and fabric integrity of LLINs through measuring holes and tears in the fabric.
- Determine insecticide Resistance in the main malaria vectors in study locations in collaboration with the NIMR insecticide resistance monitoring scheme using WHO susceptibility assays.
- Develop a GIS model for use by NMCP for insecticide resistance monitoring, with flexibility to be applied to other functions such as disease incidence or LLIN coverage
- Using the GIS model, identify geographical variations in ABCD & R components to determine specific problem areas for potential success/failure of each and combinations of the components.
- Training two Tanzanian students to PhD.
We are using a two-stage approach: Firstly, LLINs from recent net campaigns (Under 5 and Universal Coverage Campaign) will be evaluated retrospectively. Those sampled households will then be provided with one of three leading LLIN products (Olyset®, Permanet®2.0 or Netprotect®) that will be followed up for three years in a prospective study to compare the performance of the three LLIN brands under user conditions at 9, 21, 29 and 36 months post-distribution at a nationally representative level. We will develop a GIS database to understand potential spatial reasons for LLIN loss and deterioration; and to monitor insecticide resistance across the country, allowing for timely decision making in insecticide resistance management for vector control at the national level. We are also extending the current NIMR mosquito Insecticide Resistance monitoring program into additional districts and use these data sets to provide GIS maps for use in health surveillance and decision making by the National Malaria Control Program (NMCP).
Relevance to Tanzanian Public Health
The data collected will be of importance to policy makers and vector control specialists both in Tanzania and the Sub Saharan African region to inform best practice for the maintenance of high and cost-effective coverage and to maximise current gains in malaria control. We will make the data available to stakeholders including NMCP and their collaborators: MEDA, Natnets and WHO Vector Control Working Group on a 12 monthly basis throughout the life of the project to ensure that decision-making can be made in a timely fashion as data become available. We are bringing together a highly skilled multi-disciplinary team that will support Tanzanian vector control both now and in the future through the development of the GIS database and training of two Tanzanian students to PhD level.
The Research Council of Norway