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Briet O, Koenker H, Norris L, Wiegand R, Vanden Eng J, Thackeray A, Williamson J, Gimnig JE, Fortes F, Akogbeto M, Yadouleton AW, Ombok M, Bayoh MN, Mzilahowa T, Abílio AP, Mabunda S, Cuamba N, Diouf E, Konaté L, Hamainza B, Katebe-Sakala C, Ponce de León G, Asamoa K, Wolkon A, Smith SC, Swamidoss I, Green M, Gueye S, Mihigo J, Morgan J, Dotson E, Craig AS, Tan KR, Wirtz RA, Smith T. Attrition, physical integrity and insecticidal activity of long-lasting insecticidal nets in sub-Saharan Africa and modelling of their impact on vectorial capacity. Malar J 2020; 19:310. [PMID: 32859210 PMCID: PMC7456088 DOI: 10.1186/s12936-020-03383-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 08/19/2020] [Indexed: 11/25/2022] Open
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 insecticidal 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. WHO-recommended 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 entomological effects of chemical decay are relatively small, with physical decay probably more important as a driver of attrition and non-use than as a direct cause of loss of effect. Efforts to maximize LLIN impact in operational settings should focus on increasing LLIN usage, including through improvements in LLIN physical integrity. Further research is needed to understand household decisions related to LLIN use, including the influence of net durability and the presence of other nets in the household.
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Affiliation(s)
- Olivier Briet
- Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland.,University of Basel, 4001, Basel, Switzerland
| | - Hannah Koenker
- PMI VectorWorks, JHU Center for Communication Programs, Baltimore, MD, USA.,Tropical Health LLP, Baltimore, MD, USA
| | - Laura Norris
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Washington, DC, USA.,Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Ryan Wiegand
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Jodi Vanden Eng
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | | | - John Williamson
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - John E Gimnig
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Filomeno Fortes
- National Malaria Control Program (NMCP), Ministry of Health, Luanda, Angola.,Institute of Hygiene and Tropical Medicine, NOVA University Lisbon, Lisbon, Portugal
| | - Martin Akogbeto
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin
| | - Anges W Yadouleton
- Centre de Recherche Entomologique de Cotonou (CREC), Cotonou, Bénin.,Programme National de Lutte contre le Paludisme (PNLP), Ministry of Health, Cotonou, Bénin
| | - Maurice Ombok
- Kenya Medical Research Institute (KEMRI), Kisumu, Kenya
| | - M Nabie Bayoh
- Kenya Medical Research Institute (KEMRI), Kisumu, Kenya.,PMI VectorLink Project, Abt Associates, Lusaka, Zambia
| | - Themba Mzilahowa
- College of Medicine, Malaria Alert Centre, P/Bag 360, Blantyre 3, Malawi
| | - Ana Paula Abílio
- Instituto Nacional de Saúde (INS), Ministério da Saúde, Maputo, Mozambique
| | - Samuel Mabunda
- Instituto Nacional de Saúde (INS), Ministério da Saúde, Maputo, Mozambique.,National Malaria Control Programme (NMCP), Ministry of Health, Maputo, Mozambique
| | - Nelson Cuamba
- Instituto Nacional de Saúde (INS), Ministério da Saúde, Maputo, Mozambique.,National Malaria Control Programme (NMCP), Ministry of Health, Maputo, Mozambique
| | - Elhadji Diouf
- Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | - Lassana Konaté
- Faculté des Sciences et Techniques (FST), Université Cheikh Anta Diop (UCAD), Dakar, Senegal
| | | | | | - Gabriel Ponce de León
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Kwame Asamoa
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Adam Wolkon
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Stephen C Smith
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Isabel Swamidoss
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Mike Green
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Salam Gueye
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Jules Mihigo
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Juliette Morgan
- U.S. President's Malaria Initiative, Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Ellen Dotson
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Allen S Craig
- U.S. President's Malaria Initiative, Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Kathrine R Tan
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Robert A Wirtz
- Division of Parasitic Diseases and Malaria, Centers for Disease Control (CDC) and Prevention, Atlanta, GA, USA
| | - Tom Smith
- Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, 4001, Basel, Switzerland.
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