operational conditions. The persistence of insecticidal efficacy is important to estimate the
median serviceable life of nets under field conditions and to plan for net replacement.
Methods Deltamethrin residue levels were evaluated by the proxy method of X-ray
fluorescence spectrometry on 189 nets used for three to six months from nine sites, 220 nets
used for 14-20 months from 11 sites, and 200 nets used for 26-32 months from ten sites in …