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Volume 20, Number 10—October 2014

Increased Pyrethroid Resistance in Malaria Vectors and Decreased Bed Net Effectiveness, Burkina Faso

Kobié H. Toé, Christopher M. Jones, Sagnon N’Fale, Hanafy M. Ismail, Roch K. Dabiré, and Hilary RansonComments to Author 
Author affiliations: Liverpool School of Tropical Medicine, Liverpool, UK (K.H. Toé, C.M. Jones, H.M. Ismail, H. Ranson); Centre National de Recherche et de la Formation sur Paludisme, Ouagadougou, Burkina Faso (K.H. Toé, S. N’Fale); Institut de Recherche en Sciences de la Santé/Centre Muraz, Bobo-Dioulasso, Burkina Faso (R.K. Dabiré)

Main Article

Table 2

Alternative field bioassay methods for assessing strength of insecticide resistance*

Method Brief description Advantages Disadvantages
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.

Main Article

Page created: September 12, 2014
Page updated: September 12, 2014
Page reviewed: September 12, 2014
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