Determining Effectiveness of New Approaches to Dengue Vector Control in Cambodia

Background: Dengue is an important public health problem with an estimated 390 million infections annually worldwide, and an estimated 1.6 million infections annually in Cambodia. Due to the rise in dengue cases, and the current lack of widely available effective vaccines and therapeutics there is an urgent need to come up with more effective, sustainable, and locally appropriate vector control methods. Methods: A cluster randomized trial with three arms was designed to assess the impact of guppy fish (Poecilia reticulata), in combination with the larvicide pyriproxyfen (PPF), and Communication for Behavioural Impact (COMBI) activities, on entomological indices over one year in Cambodia. In addition, entomology data was used to determine the ability of the Premise Condition Index (PCI) to predict Aedes mosquito density and prioritize vector control interventions. Results: The guppy only intervention arm was able to decrease the number of Aedes females (Density Ratio (DR)=0.49) and Pupae Per Person (DR=0.56) by roughly half compared to the control arm. There were no statistical differences identified between the two intervention arms. All other entomological indices showed similar statistically significant reductions in intervention arms compared to the control arm. Data from the KAP and qualitative assessments showed community acceptance of interventions. Despite statistically significant associations between PCI scores and adult and immature Aedes densities, receiver operating characteristic curves suggest the PCI was a poor predictor of whether premises had higher densities of immature and adult Aedes mosquitoes. Conclusions: The effectiveness of interventions demonstrated in the trial along with community acceptance suggests guppies should be considered as vector control tools in Cambodia as long as the benefits outweigh any potential environmental concerns. The PCI results suggest caution is warranted in programmatic use of PCI in areas of similar geography and mosquito abundance.