AUTHOR=Koinari Melanie , Bubun Nakei , Wilson David , Anetul Evodia , Timinao Lincoln , Johnson Petrina , Daly Norelle L. , Laman Moses , Freeman Tim , Karl Stephan TITLE=Analysis of insecticides in long-lasting insecticidal nets using X-ray fluorescence spectroscopy and correlation with bioefficacy JOURNAL=Frontiers in Parasitology VOLUME=2 YEAR=2023 URL=https://www.frontiersin.org/journals/parasitology/articles/10.3389/fpara.2023.1258429 DOI=10.3389/fpara.2023.1258429 ISSN=2813-2424 ABSTRACT=Background

Long-lasting insecticidal nets (LLINs) are a key vector control tool used for the prevention of malaria. Active ingredient (AI) measurements in LLINs are essential for evaluating their quality and efficacy. The main aim of the present study was to determine the utility of X-ray fluorescence (XRF) spectroscopy as a suitable field-deployable tool for total AI quantification in LLINs.

Methods

New and unused LLIN samples containing deltamethrin (PermaNet® 2.0, n = 35) and alpha-cypermethrin (SafeNet®, n = 43) were obtained from batches delivered to Papua New Guinea (PNG) for mass distribution. Insecticides were extracted from the LLINs using a simple extraction technique and quantified using liquid chromatography mass spectrometry (LC-MS). The LC-MS results were correlated with XRF spectroscopy measurements on the same nets. Operators were blinded regarding the type of net. Bioefficacy of the LLIN samples was tested using WHO cone bioassays and test results were correlated with total AI content.

Results

The results indicate correlation between quantitative XRF and LC-MS. Interestingly, the total AI content was negatively correlated with bioefficacy in PermaNet® 2.0 (especially in recently manufactured nets). In contrast, AI content was positively correlated with bioefficacy in SafeNet®. These results indicate that the chemical content analysis in predelivery inspections does not always predict bioefficacy.

Conclusion

XRF is a promising field-deployable tool for quantification of both deltamethrin- and alpha-cypermethrin-coated LLINs. Because total AI content is not always a predictor of the efficacy of LLINs to kill mosquitoes, bioefficacy measurements should be included in predelivery inspections.