1. Chlorfenapyr LLINs provided significantly better protection than pyriproxyfen and piperonyl-butoxide subtypes.

2. Chlorfenapyr LLINs costed an additional $19 US than pyrethroid-only LLINs.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Pyrethroids have long been used to sustain effective malaria vector control. However, with growing resistance from Anopheles vectors, their effectiveness is slowly being compromised. New classes of long-lasting insecticidal nets (LLINs) are being developed to control the prevalence of malaria. This four-arm randomized trial aimed to compare the safety and efficacy of different dual-active-ingredient LLINs (pyriproxyfen, chlorfenapyr, and piperonyl butoxide) with pyrethroid-only LLINs against Plasmodium falciparum malaria infection. The primary outcome was prevalence of P. falciparum infection at 24 months from baseline while the primary economic outcome was cost-effectiveness of various dual-active-ingredient LLINs. According to study results, non-pyrethroid LLINs provided better protection than pyrethroid-only LLINs, although this difference was non-significant for the pyriproxyfen and piperonyl butoxide groups. In contrast, chlorfenapyr LLINs significantly reduced the rate of malaria infections and were found to be the most cost effective LLINs. A major limitation of this study is that it studied a single strain of malaria (P. falciparum) in a single nation of sub-Saharan Africa.

Click to read the study in The Lancet

Relevant Reading: A Monoclonal Antibody for Malaria Prevention

In-depth [randomized-controlled trial]: Between May 11 and July 2, 2018, 86 clusters were screened for eligibility in Misungwi, Tanzania. To be included, clusters must have at least 119 households containing children aged 6 months to 14 years. Altogether, 84 clusters (21 each to pyrethroid-only, pyriproxyfen, chlorfenapyr, and piperonyl-butoxide groups) were included in the intention-to-treat analysis. The primary outcome of malaria infection at 24 months was lower in the pyriproxyfen (37.5%, adjusted odds ratio [aOR] 0.79, 95% confidence interval [CI] 0.54-1.17, p=0.2354), piperonyl-butoxide (40.7%, aOR 0.99, 95% CI 0.67-1.45, p=0.9607), and chlorfenapyr (25.6%, aOR 0.45, 95% CI 0.30-0.67, p=0.0001) groups compared to pyrethroid-only reference group (45.8%). However, only chlorfenapyr LLINs provided significantly better protection at two years than pyrethroid-only LLINs. Chlorfenapyr LLINs were also the most cost-effective, costing only $19 more than standard pyrethroid-only LLINs. The most common side effects included skin irritation or paresthesia. Overall, chlorfenapyr LLINs provided significantly better protection than standard LLINs and may be considered for malaria prevention in sub-Saharan Africa.

Image: PD

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