Effect of Short-Term Heating on Bioefficacy of Deltamethrin-Coated Long-Lasting Insecticidal Nets

• Published in: The American journal of tropical medicine and hygiene Vol. 106; no. 3; pp. 828 - 830
• Main Authors: Bubun, Nakei, Freeman, Timothy W, Laman, Moses, Karl, Stephan
• Format: Journal Article
• Language: English
• Published: United States Institute of Tropical Medicine 20.12.2021; The American Society of Tropical Medicine and Hygiene
• Subjects: Animals; Anopheles; Bioassays; Heating; Humans; Insecticide Resistance; Insecticide-Treated Bednets; Insecticides - pharmacology; Mosquito Control - methods; Nitriles; Pyrethrins - pharmacology; Quality control; Short Report
• ISSN: 0002-9637; 1476-1645
• DOI: 10.4269/ajtmh.21-0613

The authors recently reported that long-lasting insecticidal nets (LLINs) distributed in Papua New Guinea (PNG) between 2013 and 2019, exhibited severely diminished efficacy to knock down and kill susceptible Anopheles mosquitoes. This coincided with a rise in malaria observed in PNG since 2015. Here, the authors show that LLIN bioefficacy is increased by heating LLINs prior to WHO cone bioassays. Unused LLINs with low bioefficacy, delivered to PNG in 2019, were heated to 120°C for 5 minutes. Cone bioassays were performed before and at 1 hour, 7 days, and 30 days after heating. This led to a significant increase in 24-hour mortality from 17% to 61% and 60-minute knock down from 31% to 72%. The effect was sustained over 30 days. Bioassays are crucial in quality assurance of LLIN products. Our findings indicate that bioefficacy of LLINs can be increased by heating. This may have implications for quality assurance procedures used to assess LLINs.