Abstract:
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Background: Progress in reducing the malaria disease burden through the substantial scale up of insecticide-based
vector control in recent years could be reversed by the widespread emergence of insecticide resistance. The impact
of insecticide resistance on the protective effectiveness of insecticide-treated nets (ITN) and indoor residual spraying
(IRS) is not known. A multi-country study was undertaken in Sudan, Kenya, India, Cameroon and Benin to quantify the
potential loss of epidemiological effectiveness of ITNs and IRS due to decreased susceptibility of malaria vectors to
insecticides. The design of the study is described in this paper.
Methods: Malaria disease incidence rates by active case detection in cohorts of children, and indicators of insecticide
resistance in local vectors were monitored in each of approximately 300 separate locations (clusters) with high
coverage of malaria vector control over multiple malaria seasons. Phenotypic and genotypic resistance was assessed
annually. In two countries, Sudan and India, clusters were randomly assigned to receive universal coverage of ITNs
only, or universal coverage of ITNs combined with high coverage of IRS. Association between malaria incidence and
insecticide resistance, and protective effectiveness of vector control methods and insecticide resistance were estimated,
respectively.
Results: Cohorts have been set up in all five countries, and phenotypic resistance data have been collected in all
clusters. In Sudan, Kenya, Cameroon and Benin data collection is due to be completed in 2015. In India data collection
will be completed in 2016.
Discussion: The paper discusses challenges faced in the design and execution of the study, the analysis plan, the
strengths and weaknesses, and the possible alternatives to the chosen study design. |