Technical consultation on specifications and quality control of netting materials and mosquito nets
4.9 Pesticide bioavailability and retention in field-treated nets
Where nets are to be treated in the field, the netting material must provide adequate retention and bioavailability of the insecticide. Producers of insecticide treatment kits and sachets are already required, by WHOPES, to specify the types of fabric/net for which the insecticide dose is intended, as well as the expected wash resistance of the treatment and its duration. Current WHO recommendations are that field-treated nets should be retreated after three washes or at least once per year. Bioavailability and wash resis- tance of the insecticide on the net are key characteristics of the quality of insecticide treatment of nets in the field. The meeting noted that bioavailabil- ity, as measured by bioassay, is difficult to relate to analytical measurements.