Volume 20, Number 10—October 2014
Increased Pyrethroid Resistance in Malaria Vectors and Decreased Bed Net Effectiveness, Burkina Faso
|Time-response curves (LT50)||Exposure to fixed concentration of insecticide for varying periods||Can be performed by using diagnostic dose filter papers available from WHO; simple to perform||Not appropriate for highly resistant mosquito populations in which long exposure times required|
|Dose-response curves (LD50)||Exposure to varying concentrations of insecticide for a fixed period||Can be readily adapted for populations of different resistance status by varying concentration of insecticide used||Challenging to accurately measure small quantities of insecticide needed for some pyrethroid insecticides; if bottles are reused, stringent washing conditions are needed|
|Cone bioassays on treated surfaces||Exposure to field dose of insecticide for fixed period||Concentration of insecticide being evaluated is the field dose||Mosquitoes can avoid exposure by resting on side of cones, particularly for new preparations of some pyrethroids.|
*For all assays, use of age-standardized mosquitoes and inclusion of a 24-h recovery period to capture metabolic resistance mechanisms (which can be slower to act) is recommended. LT50, 50% lethality time; WHO, World Health Organization; LD50, 50% lethal dose.