Case-area targeted interventions (CATI) for reactive dengue control: Modelling effectiveness of vector control and prophylactic drugs in Singapore.

Oliver J Brady,Adam J Kucharski,Martin L Hibberd,Joris Menten,Shuzhen Sim,Yalda Jafari,Guillermo Herrera-Taracena,Marnix Van Loock,W John Edmunds,Sebastian Funk,Lee-Ching Ng,Stéphane Hué

doi:10.1371/journal.pntd.0009562

Abstract

Targeting interventions to areas that have recently experienced cases of disease is one strategy to contain outbreaks of infectious disease. Such case-area targeted interventions (CATI) have become an increasingly popular approach for dengue control but there is little evidence to suggest how precisely targeted or how recent cases need to be, to mount an effective response. The growing interest in the development of prophylactic and therapeutic drugs for dengue has also given new relevance for CATI strategies to interrupt transmission or deliver early treatment. Here we develop a patch-based mathematical model of spatial dengue spread and fit it to spatiotemporal datasets from Singapore. Simulations from this model suggest CATI strategies could be effective, particularly if used in lower density areas. To maximise effectiveness, increasing the size of the radius around an index case should be prioritised even if it results in delays in the intervention being applied. This is partially because large intervention radii ensure individuals receive multiple and regular rounds of drug dosing or vector control, and thus boost overall coverage. Given equivalent efficacy, CATIs using prophylactic drugs are predicted to be more effective than adult mosquito-killing vector control methods and may even offer the possibility of interrupting individual chains of transmission if rapidly deployed. CATI strategies quickly lose their effectiveness if baseline transmission increases or case detection rates fall. These results suggest CATI strategies can play an important role in dengue control but are likely to be most relevant for low transmission areas where high coverage of other non-reactive interventions already exists. Controlled field trials are needed to assess the field efficacy and practical constraints of large operational CATI strategies.

Highlights

Dengue is a viral disease vectored by the Aedes aegypti mosquito that causes an estimated 100– 400 million infections per year worldwide [1, 2]
One option is to use case-area targeted interventions (CATI) that are focussed on areas that have recently reported disease cases
The effectiveness of such CATI strategies is highly dependent on how the disease spreads

Summary

Introduction

Dengue is a viral disease vectored by the Aedes aegypti mosquito that causes an estimated 100– 400 million infections per year worldwide [1, 2]. One strategy recommended to achieve this is the use of case-area targeted interventions (CATI), where interventions are targeted in and around (typically within 100m) the houses of dengue patients after they present to healthcare facilities [3] These interventions are currently restricted to vector control activities including fogging to kill adult mosquitoes and source reduction to eliminate mosquito egg-laying habitat [4]. Targeting interventions to areas that have recently experienced cases of disease is one strategy to contain outbreaks of infectious disease Such case-area targeted interventions (CATI) have become an increasingly popular approach for dengue control but there is little evidence to suggest how precisely targeted or how recent cases need to be, to mount an effective response.

Objectives

Methods

Results

Discussion

Conclusion