Cluster Randomised Trial to Compare Effectiveness of Bendiocarb and Deltamethrin (Long-Lasting) in Preventing Malaria Infection

In 2013, a new long lasting pyrethroid insecticide, K-Othrine SC 62.5, that has been developed by Bayer AG, was used for the IRS program in Bioko Island, Equatorial Guinea, for the first time. This change coincided with a marked increase in parasite prevalence in 2-14 year olds as measured in the Annual Malaria Indicator Survey (14% to 28%, respectively). In order to determine whether the change in insecticide caused the increase in prevalence, a cluster randomized control trial was designed.

Twenty-four (24) clusters, each containing between 250-300 houses were selected throughout Bioko Island. Clusters were chosen with an attempt to maximize the geographical space between clusters (to minimize possible residual effects from insecticides), while ensuring that areas with historically higher acceptance rates for Indoor Residual Spraying (IRS) were selected. Each cluster had a buffer zone of 300m (or halfway between clusters less than 600m apart).

A team of 10 local surveyors conducted a baseline survey in each cluster area, measuring prevalence through malaria Rapid Diagnostic Test (RDT) positivity, net ownership, spray coverage, and hemoglobin levels. Approximately 100 children in each cluster were tested. These data were then used for a restricted randomization. Each cluster was then sprayed with either deltamethrin or bendiocarb, depending on randomization. The IRS team put equal amount of effort into each cluster, as determined by number of sprayers/house/day in an attempt to minimize bias.

An end-line survey was conducted using an ODK Collect application in the same cluster areas. Prevalence was measured by RDT, and hemoglobin data was gathered. In addition, the head of household was asked about the acceptability to IRS and their willingness to receive the insecticide in a future round.