Mosquito nets treated with a synergist piperonyl butoxide (PBO) long-lasting insecticidal proved to be more effective than nets treated with standard long-lasting pyrethroid in protecting against malaria infection and transmission, according to new research published in the Lancet.

Long-lasting insecticidal nets and indoor residual spraying have been very effective in reducing malaria-related morbidity in sub-Saharan Africa, but new strategies and approaches are needed to address the growing threat of resistance, note the authors.

In the current study, the effectiveness of PBO long-lasting insecticidal nets was compared with the standard currently in use, in a 4-group cluster randomized controlled trial ( identifier: NCT02288637). Using a 2-by-2 factorial design of 48 clusters derived from 40 Tanzanian villages, clusters were assigned to 1 of the following: standard long-lasting insecticidal nets, PBO long-lasting insecticidal nets, standard long-lasting insecticidal nets plus indoor residual spraying, or PBO long-lasting insecticidal nets plus indoor residual spraying.

After 9 months, the prevalence of malaria infection was lower in the 2 groups that received PBO long-lasting insecticidal nets compared with the groups using standard long-lasting insecticidal nets (531 [29%] of 1852 children vs 767 [42%] of 1809; odds ratio [OR] 0.37; 95% CI, 0.21-0.65; P =.0011). In addition, malaria prevalence in the 2 groups that received indoor residual spraying was lower compared with those that did not (508 [28%] of 1846 children vs 790 [44%] of 1815; OR 0.33; 95% CI 0.19-0.55; P <.0001). The effect of the PBO net was sustained after 21 months, with a lower malaria prevalence vs the standard net (865 [45%] of 1930 children vs 1255 [62%] of 2034; OR 0.40; 95% CI, 0.20-0.81; P =.0122).

Overall, the addition of the PBO long-lasting insecticidal nets was associated with a 44% protective efficacy after 1 year, and 33% at the end of the second year, vs standard netting.

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“This study provides justification for the increase in deployment and use of PBO long-lasting insecticidal nets,” write the authors, noting that as a direct consequence of this trial, the World Health Organization revised its policy on long-lasting insecticidal nets and gave interim endorsement to pyrethroid-PBO nets as a new World Health Organization class of vector control product.


Protopopoff N, Mosha JF, Lukole E, et al. Effectiveness of a long-lasting piperonyl butoxide-treated insecticidal net and indoor residual spray interventions, separately and together, against malaria transmitted by pyrethroid-resistant mosquitoes: a cluster, randomised controlled, two-by-two factorial design trial [published online April 11, 2018]. Lancet. doi: 10.1016/S0140-6736(18)30427-6