Entomological outcomes of cluster-randomised, community-driven dengue vector-suppression interventions in Kampong Cham province, Cambodia.

Jacob Bigio,John Hustedt,Sokha Suon,Jeffrey Hii,Pierre Echaubard,Thy Chea,Bernadette Ramirez,Didot Budi Prasetyo,Mark Debackere,Srun Set,Alexandra Wharton-Smith,Sam Bunleng,Leo Braack

doi:10.1371/journal.pntd.0010028

Abstract

Cambodia has one of the highest dengue infection rates in Southeast Asia. Here we report quantitative entomological results of a large-scale cluster-randomised trial assessing the impact on vector populations of a package of vector control interventions including larvivorous guppy fish in household water containers, mosquito trapping with gravid-ovitraps, solid waste management, breeding-container coverage through community education and engagement for behavioural change, particularly through the participation of school children. These activities resulted in major reductions in Container Index, House Index, Breteau Index, Pupal Index and Adult Index (all p-values 0.002 or lower) in the Intervention Arm compared with the Control Arm in a series of household surveys conducted over a follow-up period of more than one year, although the project was not able to measure the longer-term sustainability of the interventions. Despite comparative reductions in Adult Index between the study arms, the Adult Index was higher in the Intervention Arm in the final household survey than in the first household survey. This package of biophysical and community engagement interventions was highly effective in reducing entomological indices for dengue compared with the control group, but caution is required in extrapolating the reduction in household Adult Index to a reduction in the overall population of adult Aedes mosquitoes, and in interpreting the relationship between a reduction in entomological indices and a reduction in the number of dengue cases. The package of interventions should be trialled in other locations.

Highlights

Dengue is the most common and widely distributed human arbovirus, with an estimated 390 million infections and 90 million cases per year [1]
In Cambodia, mosquitoes which can carry dengue virus breed in fresh water collected in containers such as the large clay jars used for domestic water storage in the many rural parts of the country which lack piped household water supply
This study examined a package of interventions including putting mosquito larvae-eating guppy fish in household water containers, trapping adult mosquitoes, removing mosquito breeding sites from around houses and providing community education about dengue, to school children

Summary

Introduction

Dengue is the most common and widely distributed human arbovirus, with an estimated 390 million infections and 90 million cases per year [1]. Cambodia has one of the highest dengue infection rates in Southeast Asia, with an average 103 cases per 10,000 population reported annually to the national surveillance system [7]. Dengue in Cambodia is transmitted by both Aedes aegypti and Aedes albopictus. Vector control strategies in Cambodia have focused on the use of the larvicide temephos in these household water containers and on thermal fogging with pyrethroids [10,11]. Work showing widespread resistance to deltamethrin, permethrin and temephos among Aedes aegypti in Cambodia suggests a need for control strategies which do not rely upon these insecticides [12]

Methods

Results

Conclusion