Field efficacy of a new mosaic long-lasting mosquito net (PermaNet® 3.0) against pyrethroid-resistant malaria vectors: a multi centre study in Western and Central Africa

Background: Due to the spread of pyrethroid-resistance in malaria vectors in Africa, new strategies and tools are urgently needed to better control malaria transmission. The aim of this study was to evaluate the performances of a new mosaic long-lasting insecticidal net (LLIN), i.e. PermaNet (R) 3.0, against wild pyrethroid-resistant Anopheles gambiae s.l. in West and Central Africa. Methods: A multi centre experimental hut trial was conducted in Malanville (Benin), Vallee du Kou (Burkina Faso) and Pitoa (Cameroon) to investigate the exophily, blood feeding inhibition and mortality induced by PermaNet (R) 3.0 (i.e. a mosaic net containing piperonyl butoxide and deltamethrin on the roof) comparatively to the WHO recommended PermaNet (R) 2.0 (unwashed and washed 20-times) and a conventionally deltamethrin-treated net (CTN). Results: The personal protection and insecticidal activity of PermaNet 3.0 and PermaNet (R) 2.0 were excellent (>80%) in the pyrethroid-tolerant area of Malanville. In the pyrethroid-resistance areas of Pitoa (metabolic resistance) and Vallee du Kou (presence of the L1014F kdr mutation), PermaNet (R) 3.0 showed equal or better performances than PermaNet (R) 2.0. It should be noted however that the deltamethrin content on PermaNet (R) 3.0 was up to twice higher than that of PermaNet (R) 2.0. Significant reduction of efficacy of both LLIN was noted after 20 washes although PermaNet (R) 3.0 still fulfilled the WHO requirement for LLIN. Conclusion: The use of combination nets for malaria control offers promising prospects. However, further investigations are needed to demonstrate the benefits of using PermaNet (R) 3.0 for the control of pyrethroid resistant mosquito populations in Africa.