Long-Lasting Insecticidal Nets Incorporating Piperonyl Butoxide Reduce the Risk of Malaria in Children in Western Kenya: A Cluster Randomized Controlled Trial

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  • 1 Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan;
  • 2 Kenya Medical Research Institute, Nairobi, Kenya;
  • 3 Center for Research in Tropical Medicine and Community Development (CRTMCD), Nairobi, Kenya;
  • 4 Ability to Solve by Knowledge Project, Mbita, Kenya

Malaria vectors have acquired an enzyme that metabolizes pyrethroids. To tackle this problem, we evaluated long-lasting insecticidal nets incorporating piperonyl butoxide (PBO-LLINs) with a community-based cluster randomized control trial in western Kenya. The primary endpoints were anopheline density and Plasmodium falciparum polymerase chain reaction (PCR)-positive prevalence (PCRpfPR) of children aged 7 months to 10 years. Four clusters were randomly selected for each of the treatment and control arms (eight clusters in total) from 12 clusters, and PBO-LLINs and standard LLINs were distributed in February 2011 to 982 and 1,028 houses for treatment and control arms, respectively. Entomological surveys targeted 20 houses in each cluster, and epidemiological surveys targeted 150 children. Cluster-level permutation tests evaluated the effectiveness using the fitted values from individual level regression models adjusted for baseline. Bootstrapping estimated 95% confidence intervals (CIs). The medians of anophelines per house were 1.4 (interquartile range [IQR]: 2.3) and 3.4 (IQR: 3.7) in the intervention and control arms after 3 months, and 0.4 (IQR: 0.2) and 1.6 (IQR: 0.5) after 10 months, respectively. The differences were –2.5 (95% CI: –6.4 to –0.6) and –1.3 (95% CI: –2.0 to –0.7), respectively. The datasets of 861 and 775 children were analyzed in two epidemiological surveys. The median PCRpfPRs were 25% (IQR: 11%) in the intervention arm and 52% (IQR: 11%) in the control arm after 5 months and 33% (IQR: 11%) and 45% (IQR: 5%) after 12 months. The PCRpfPR ratios were 0.67 (95% CI: 0.38, 0.91) and 0.74 (95% CI: 0.53, 0.90), respectively. We confirmed the superiority of PBO-LLINs.

Author Notes

Address correspondence to Noboru Minakawa, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan. E-mail: minakawa@nagasaki-u.ac.jp

Financial support: This study was funded as a joint research between Nagasaki University and Sumitomo Chemical Co. Ltd., and partially supported by the Global Center of Excellence Program, Nagasaki University, Japan. The funders had no role in study design, data collection and analysis, decision to publish, and preparation of the manuscript.

Disclosure: Although this study was partially funded by the manufacture (Sumitomo Chemical Co. Ltd) of OlysetNet and OlysetPlus, the authors have no other financial competing interests and nonfinancial competing interests.

Authors’ addresses: Noboru Minakawa, Hitoshi Kawada, Rie Isozumi, and Kyoko Futami, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Sakamoto, Nagasaki, Japan, E-mails: minakawa @nagasaki-u.ac.jp, vergiss_mine_nicht@hotmail.com, wushiqilihui@hotmail.co.jp, and kfmospi@gmail.com. James O. Kongere and Peter A. Lutiali, Center for Research in Tropical Medicine and Community Development, NUITM-KEMRI, Kenya Medical Research Institute, Nairobi, Kenya, E-mails: jkongere@gmail.com and pakweywa@yahoo.com. George O. Sonye and Beatrice Awuor, Ability to Solve by Knowledge Project, Mbita, Kenya, E-mails: sukumaotieno@gamil.com and awuorb5@gmail.com.