A Rapid, Affordable and Simple Technique to Determine whether a Bednet Remains Effective

 A study performed by ISGlobal, in collaboration with other Catalan centers, evaluates different analytical methods to measure the amount of pyrethroids on bednets and shows that one of these techniques can be easily applied in the field and at an affordable cost. The study, resulting from the collaboration of researchers from both areas of the institute (infectious diseases and non-communicable diseases and environment), should help establish clear guidelines on the use and replacement of bednets in the field.

The use of insecticides within houses and on bednets constitutes the cornerstone of most vector control programs that aim to reduce the incidence of vector-borne diseases such as malaria or dengue. Given their safety and efficacy, pyrethroids are the most frequently used insecticides to treat bednets.  The half-life of such bednets (i.e. the time during which the insecticide maintains its activity) is determined in the laboratory, but is influenced by local environmental factors and user handling. Hence, there is need to develop simple and rapid field tests to determine insecticide concentrations on surfaces such as bednets or walls. 

In this study, the authors evaluated three detection methods based on an immunoassay for the recognition of the insecticide on treated surfaces (pyrethroids in this case). The first one (ELISA) is sensitive and quantitative but adequate for use in the laboratory. The second one (biosensors with EIS) is sensitive, quicker (30 minutes) and semi-quantitative but not easy to implement in the field. The third one (LFIA) turned out to be quick (5 minutes per test), cheap (1€ or less per test), portable and simple to use in the field. Despite being more qualitative than quantitative, it is useful to determine whether an insecticide-treated bednet (ITN) is still effective against mosquitoes or not. In addition, the authors validated a simple method to extract the insecticide from the treated material in order to measure it.

“The advantage”, explains Albert Picado, ISGlobal researcher and senior author of the study, “is that this type of immunochemical approach allows detecting other insecticides on the net, or even new molecules that are under evaluation.  We just need to develop the appropriate reagents”.  The authors conclude that the LFIA developed in the study represents “the most promising approach to a field-friendly and affordable semiquantitative test for insecticide concentration in ITNs” and should help establish guidelines for the use and replacement of such nets in the field.  

Reference

Castellarnau M, Ramón-Azcón J, Gonzalez-Quinteiro Y, López JF, Grimalt JO, Marco MP, Nieuwenhuijsen M, Picado A. Assessment of analytical methods to determine pyrethroids content of bednets. Trop Med Int Health. 2016 Oct 7.