Multi-country evaluation of the durability of pyrethroid plus piperonyl-butoxide insecticide-treated nets: study protocol

Abstract

Abstract Background Mass distributions of long-lasting insecticidal nets (LLINs) has contributed to large reductions in the malaria burden. However, this success is in jeopardy due in part to the increasing pyrethroid-resistant mosquito population as well as low LLINs coverage in various areas because the lifespan of LLINs is often shorter than the interval between replenishment campaigns. New insecticide-treated nets (ITNs) containing pyrethroid and piperonyl-butoxide (PBO) have shown a greater reduction in the incidence of malaria than pyrethroid LLINs in areas with pyrethroid-resistant mosquitoes. However, the durability of pyrethroid-PBO ITNs under operational settings is not fully characterized. This study will measure the bioefficacy and physical durability of pyrethroid-PBO ITNs over three years to assess whether they meet the World Health Organisation (WHO) three years operational performance criteria required to be categorised as “long-lasting”. Methods A prospective household randomized controlled trial will be conducted simultaneously in Tanzania, India and Côte d’Ivoire to estimate the field durability of three pyrethroid-PBO ITNs (Veeralin®, Tsara® Boost, and Olyset® Plus) compared to a pyrethroid LLIN: MAGNet®. Durability monitoring will be conducted up to 36 months post-distribution and median survival in months will be calculated. The proportion of ITNs lost (attrition), the physical integrity of the nets, resistance to damage score, the proportion of ITNs meeting WHO bioefficacy criteria against laboratory-reared resistant and susceptible mosquitoes, and insecticidal persistence over time will be estimated. The non-inferiority of Veeralin® and Tsara® Boost to the first-in-class, Olyset® Plus will be assessed for mortality, and the equivalence of 20 times washed ITNs compared to field aged ITNs will be assessed for mortality and blood-feeding inhibition endpoints in the Ifakara Ambient Chamber Test, Tanzania. Discussion This will be the first large-scale prospective household randomised controlled trial of pyrethroid-PBO ITNs in three different countries representing East Africa, West Africa and South Asia region simultaneously. The study findings will generate information on average replenishment intervals for PBO nets.