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

• Published in: Scientific reports 2018-11, Vol.8 (1), p.16769-8, Article 16769
• Main Authors: Boyer, Sebastien, Pothin, Emilie, Randriamaherijaona, Sanjiarizaha, Rogier, Christophe, Kesteman, Thomas
• Format: Article
• Language: English
• Subjects: 631/601/1466; 692/699/255/1629; Aquatic insects; Bayesian analysis; Control programs; Culicidae; Humanities and Social Sciences; Insecticides; Laboratory methods; Life Sciences; Malaria; Mortality; Mosquitoes; multidisciplinary; Nets; Other; Public health; Science; Science (multidisciplinary); Vector-borne diseases
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-34979-3

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.