A SIMPLE FIELD-TEST FOR DETECTING PYRETHROIDS ON IMPREGNATED NETS

We tested a modified Beilstein method for detecting pyrethroids on bed nets under laboratory conditions using an emulsifiable concentrate of permethrin (50 EC) for viability as a simple standardized field test a nd to judge its reliability for detecting different insecticide doses. At the recommended doses of permethrin (0.5 g/m(2)), sensitivity was near 100%, even when small pieces of fabric were tested and time of ex traction was limited. In unwashed nets sensitivity stayed high (80-95% ) down to 0.1 g active ingredient/m(2). In untreated nets false positi ves were rare (0-2%). The test could become a valuable tool in vector control programmes: it is cheap, easy to learn and to perform. The Lot Quality Assurance Sampling method, using an upper and lower performan ce threshold, could be applied for monitoring the impregnation campaig ns.