Testing bio-efficacy of insecticide-treated nets with fewer mosquitoes for enhanced malaria control

Sébastien Boyer (1, 2) , Emilie Pothin (3) , Sanjiarizaha Randriamaherijaona (1, 4) , Christophe Rogier (5, 6, 7) , Thomas Kesteman (5, 8)

1 IPM - Unité d'Entomologie Médicale [Antananarivo, Madagascar]
2 Institut Pasteur du Cambodge
3 Swiss Tropical and Public Health Institute [Basel]
4 Ecole doctorale Science de la vie et de l'Environnement
5 Institut Pasteur de Madagascar
6 URMITE - Unité de Recherche sur les Maladies Infectieuses Tropicales Emergentes
7 IRBA - Institut de Recherche Biomédicale des Armées [Brétigny-sur-Orge]
8 Fondation Mérieux

Malaria control programs implementing Long-Lasting Insecticidal Nets (LLINs) are encouraged to conduct field monitoring of nets' survival, fabric integrity and insecticidal bio-efficacy. The reference method for testing the insecticide activity of LLINs needs 100 two-to-five-day-old female mosquitoes per net, which is highly resource-intensive. We aimed at identifying an alternative protocol, using fewer mosquitos, while ensuring a precision in the main indicator of ±5 percentage points (pp). We compared different laboratory methods against the probability of the LLIN to fail the test as determined by a hierarchical Bayesian model. When using 50 mosquitoes per LLIN and considering mortality only instead of mortality or knock-down as validity criteria, the average error in the measure of the proportion of nets considered as valid was 0.40 pp. The 95% confidence interval of this value never exceed 5 pp when the number of LLIN tested was ≥40. This method slightly outperforms the current recommendations. As a conclusion, testing the bio-efficacy of LLINs with half as many mosquitoes provides a valid evaluation of the proportion of valid LLINs. This approach could increase entomology labs' testing capacity and decrease costs, with no impact in the decision process for public health purposes.

Domaines: Autre [q-bio.OT]

Sébastien Boyer, Emilie Pothin, Sanjiarizaha Randriamaherijaona, Christophe Rogier, Thomas Kesteman. Testing bio-efficacy of insecticide-treated nets with fewer mosquitoes for enhanced malaria control. Scientific Reports, 2018, 8 (1), pp.16769. ⟨10.1038/s41598-018-34979-3⟩. ⟨pasteur-01968115⟩