Evaluation of Field Performance of Insecticide-Treated Mosquito Nets in North-Western Burkina Faso

Aims: The aim of the study was to evaluate the field performance of insecticide-treated mosquito nets (ITNs) in north-western Burkina Faso.
Study design: Cross-sectional survey.
Place and Duration: The study took place between September and November 2008 (end of rainy season) in rural north-western Burkina Faso.
Methodology: Standard WHO bioassays were performed on field-collected ITNs from three areas of different insecticide pressure: semi-urban Nouna town, three villages with cotton agriculture, and three villages without cotton agriculture. Data on age and washing frequency of ITNs was collected, and deltamethrin content was determind by HPLC.
Results: The mean age of field-collected ITNs was 2.1 years. The mosquito mortality rate (Anopheles gambiae sl.) after 24 hours was 4% for the negative controls, 90% for the positive controls, and 73% for field-used ITNs. Differences in mosquito mortality between sub-areas disappeared after controlling for confounding variables.
Conclusion: This study demonstrates that under real life conditions, deltamethrin still shows some level of effectiveness despite ongoing insecticide pressure. However, deltamethrin resistance has been observed in other parts of the country and thus close surveillance of ITN efficacy is needed. More frequent replacement of ITNs is also recommended.