Kleinschmidt I, et al. - Researchers examined if insecticide resistance was associated with loss of effectiveness of long-lasting insecticidal nets and increased malaria disease burden. They noted insecticide resistance, despite this, researchers recommend continuous use of long-lasting insecticidal nets to reduce the risk of infection. Prioritizing the development of additional vector control tools is suggested to reduce the unacceptably high malaria burden as nets provide only partial protection.

Methods

• At 279 clusters (villages or groups of villages in which phenotypic resistance was measurable) in Benin, Cameroon, India, Kenya, and Sudan, researchers conducted this WHO-coordinated, prospective, observational cohort study.
• The principal form of malaria vector control included pyrethroid long-lasting insecticidal nets in all study areas; indoor residual spraying supplemented this approach in Sudan.
• They recruited cohorts of children from randomly selected households in each cluster.
• Community health workers followed up these cohorts to measure incidence of clinical malaria and prevalence of infection.
• They used the standard WHO bioassay test to assess the susceptibility to pyrethroids in mosquitoes.
• Meta-analysis was utilized to combine country-specific results.

Results

• Researchers enrolled 40,000 children from June 2, 2012, to Nov 4, 2016.
• Assessment of these children was performed for clinical incidence during 1·4 million follow-up visits.
• For insecticide resistance, 80,000 mosquitoes were assessed.
• Lower infection prevalence (adjusted odds ratio [OR] 0·63, 95% CI 0·51–0·78) and disease incidence (adjusted rate ratio [RR] 0·62, 0·41–0·94) were noted among long-lasting insecticidal net users than among non-users across a range of resistance levels.
• No evidence suggested an association between insecticide resistance and infection prevalence (adjusted OR 0·86, 0·70–1·06) or incidence (adjusted RR 0·89, 0·72–1·10).
• Despite significantly better protected than non-users, users of nets were nevertheless subject to high malaria infection risk (ranging from an average incidence in net users of 0·023, [95% CI 0·016–0·033] per person-year in India, to 0·80 [0·65–0·97] per person year in Kenya; and an average infection prevalence in net users of 0·8% [0·5–1·3] in India to an average infection prevalence of 50·8% [43·4–58·2] in Benin).