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

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  • 1 Vector-Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea;
  • | 2 Rotarians Against Malaria Papua New Guinea, Port Moresby, National Capitol District, Papua New Guinea;
  • | 3 Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, Queensland, Australia

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 (17–61%) and 60-minute knock down (31–72%). 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.

Author Notes

Address correspondence to Stephan Karl, Australian Institute of Tropical Health and Medicine, James Cook University, Building E4, Smithfield, Queensland 4870, Australia. E-mail: stephan.karl@jcu.edu.au

Financial support: S. K. is supported by an NHMRC Fellowship (GNT 1141441). This study was supported in part by an NHMRC Ideas Grant (GNT 2004390).

Authors’ addresses: Nakei Bubun, Vector-Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea, E-mail: kesopbubun2@gmail.com. Timothy W. Freeman, Rotarians Against Malaria Papua New Guinea, Port Moresby, National Capitol District, Papua New Guinea, E-mail: rampm@rampng.org. Moses Laman, Vector-Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea, E-mail: drmlaman@yahoo.com. Stephan Karl, Vector-Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea, and Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, Queensland, Australia, E-mail: stephanunkarl@googlemail.com.

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