PermaNet Dual, a new deltamethrin-chlorfenapyr mixture net, shows improved efficacy against pyrethroid-resistant Anopheles gambiae sensu lato in southern Benin

Abstract

Pyrethroid-chlorfenapyr nets have demonstrated improved entomological and epidemiological impact in trials across Africa. This is driving increased demand for this novel net class in malaria-endemic countries. PermaNet Dual is a new deltamethrin-chlorfenapyr net developed by Vestergaard Sàrl to provide more options to malaria control programmes. We performed an experimental hut trial to evaluate the efficacy of PermaNet Dual against wild, free-flying pyrethroid-resistant Anopheles gambiae sensu lato in Covè, Benin. PermaNet Dual induced superior levels of mosquito mortality compared to a pyrethroid-only net and a pyrethroid-piperonyl butoxide net both when unwashed (77% with PermaNet Dual vs. 23% with PermaNet 2.0 and 56% with PermaNet 3.0, p < 0.001) and after 20 standardised washes (75% with PermaNet Dual vs. 14% with PermaNet 2.0 and 30% with PermaNet 3.0, p < 0.001). Using a provisional non-inferiority margin defined by the World Health Organisation, PermaNet Dual was also non-inferior to a pyrethroid-chlorfenapyr net that has demonstrated improved public health value (Interceptor G2), for vector mortality (79% vs. 76%, OR = 0.878, 95% CIs 0.719–1.073) but not for blood-feeding protection (35% vs. 26%, OR = 1.424, 95% CIs 1.177–1.723). PermaNet Dual presents an additional option of this highly effective net class for improved control of malaria transmitted by pyrethroid-resistant mosquitoes.

Laboratory evaluation of the regeneration time, efficacy and wash-resistance of PermaNet® Dual (a deltamethrin-chlorfenapyr net) against susceptible and pyrethroid-resistant strains ofAnopheles gambiae

“…In laboratory studies, the ability of an ITN to remain effective over several years is assessed by subjecting nets to bioassays and chemical analysis for up to 20 standardised washes – a surrogate for insecticidal loss over 3 years of field use assuming nets are washed every few months (19). Both pyrethroid-CFP ITNs met WHO efficacy thresholds in tunnel tests after 20 washes corroborating previous studies (22, 30, 31) and thus showing their potential to remain efficacious over several years of household use. This suggests that the lower total CFP content retention observed with PermaNet® Dual compared to Interceptor® G2 had little or no impact on the durability of its insecticidal activity.…”

“…Hence, the superior performance of PermaNet® Dual against the susceptible strain in cone bioassays was probably due to the higher loading dose and surface availability of pyrethroid in PermaNet® Dual rather than differences in the type of pyrethroid used on each net. The comparable performance of PermaNet® Dual and Interceptor® G2 against pyrethroid-resistant mosquitoes is consistent with a recent experimental hut trial in Benin which demonstrated the non-inferiority of PermaNet® Dual to Interceptor® G2 against wild, pyrethroid-resistant mosquitoes (30). Based on this and similar evidence of efficacy from trials in Côte d’Ivoire (31) and Kenya (22), PermaNet® Dual was added to the WHO list of prequalified vector control products (17) and included in the recent policy recommendation for pyrethroid-CFP ITNs (22).…”

Efficacy of the PermaNet Dual compared to the Interceptor G2 and the PermaNet 3.0 in experimental huts in Siaya County, western Kenya.

“…funestus mosquitoes relative to the control in the experimental huts. PermaNet Dual induced the highest mortality rates which was not signi cantly different from Interceptor G2 but was signi cantly higher than PermaNet 3.0 at corroborating results from previous hut trials in Benin [32]. Similar observations have been made in experimental hut trials evaluating PermaNet Dual and Interceptor G2 where in each instance, the pyrethroid-chlorfenapyr LLIN induced higher mortality than the pyrethroid-PBO or pyrethroid only LLINs [23,32,33].…”

“…This shows the contribution of chlorfenapyr to the control of resistant mosquitoes where mechanisms other than P450 monooxygenases are active such as in this population. Similar ndings have been documented in Tanzania [10], where there was a higher impact on entomological outcomes in clusters with Interceptor G2 than those with PermaNet 3.0, and in another experimental hut trial evaluating the non-inferiority of PermaNet Dual to Interceptor G2 [32].…”

“…PermaNet Dual and Interceptor G2 did not have reductions in induced mortality or blood feeding inhibition after 20 washes, indicating good wash resistance, which is the current standard WHO proxy for an LLIN giving good performance for up to three years of use, despite less than 50% AI retention in the PermaNet Dual. Previous studies have reported similar results [32,33].…”