Attrition, physical integrity and insecticidal activity of long-lasting insecticidal nets in sub-Saharan Africa and mode
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Malaria Journal Open Access
RESEARCH
Attrition, physical integrity and insecticidal activity of long‑lasting insecticidal nets in sub‑Saharan Africa and modelling of their impact on vectorial capacity Olivier Briet1,2, Hannah Koenker3,4, Laura Norris5,6, Ryan Wiegand7, Jodi Vanden Eng7, Alex Thackeray8, John Williamson7, John E. Gimnig7 , Filomeno Fortes9,10, Martin Akogbeto11, Anges W. Yadouleton11,12, Maurice Ombok13, M. Nabie Bayoh13,14, Themba Mzilahowa15, Ana Paula Abílio16, Samuel Mabunda16,17, Nelson Cuamba16,17, Elhadji Diouf18, Lassana Konaté18, Busiku Hamainza19, Cecilia Katebe‑Sakala19, Gabriel Ponce de León7, Kwame Asamoa7, Adam Wolkon7, Stephen C. Smith7, Isabel Swamidoss7, Mike Green7, Salam Gueye7, Jules Mihigo7, Juliette Morgan20, Ellen Dotson7, Allen S. Craig20, Kathrine R. Tan7, Robert A. Wirtz7 and Tom Smith1,2*
Abstract Background: Long-lasting insecticidal nets (LLINs) are the primary malaria prevention and control intervention in many parts of sub-Saharan Africa. While LLINs are expected to last at least 3 years under normal use conditions, they can lose effectiveness because they fall out of use, are discarded, repurposed, physically damaged, or lose insecti‑ cidal activity. The contributions of these different interrelated factors to durability of nets and their protection against malaria have been unclear. Methods: Starting in 2009, LLIN durability studies were conducted in seven countries in Africa over 5 years. WHOrecommended measures of attrition, LLIN use, insecticidal activity, and physical integrity were recorded for eight different net brands. These data were combined with analyses of experimental hut data on feeding inhibition and killing effects of LLINs on both susceptible and pyrethroid resistant malaria vectors to estimate the protection against malaria transmission—in terms of vectorial capacity (VC)—provided by each net cohort over time. Impact on VC was then compared in hypothetical scenarios where one durability outcome measure was set at the best possible level while keeping the others at the observed levels. Results: There was more variability in decay of protection over time by country than by net brand for three measures of durability (ratios of variance components 4.6, 4.4, and 1.8 times for LLIN survival, use, and integrity, respectively). In some countries, LLIN attrition was slow, but use declined rapidly. Non-use of LLINs generally had more effect on LLIN impact on VC than did attrition, hole formation, or insecticide loss. Conclusions: There is much more variation in LLIN durability among countries than among net brands. Low levels of use may have a larger impact on effectiveness than does variation in attrition or LLIN degradation. The estimated
*Correspondence: Thomas‑[email protected] 2 University of Basel, 4001 Basel, Switzerland Full list of author information is available at the end of the article © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distr
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