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Spatial spillover analysis of a cluster-randomized trial against dengue vectors in Trujillo, Venezuela

Alexander, Neal, Lenhart, Audrey and Anaya-Izquierdo, Karim (2020) 'Spatial spillover analysis of a cluster-randomized trial against dengue vectors in Trujillo, Venezuela'. PLoS Neglected Tropical Diseases, Vol 14, Issue 9, e0008576.

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The ability of cluster-randomized trials to capture mass or indirect effects is one reason for their increasing use to test interventions against vector-borne diseases such as malaria and dengue. For the same reason, however, the independence of clusters may be compromised if the distances between clusters is too small to ensure independence. In other words they may be subject to spillover effects.

We distinguish two types of spatial spillover effect: between-cluster dependence in outcomes, or spillover dependence; and modification of the intervention effect according to distance to the intervention arm, or spillover indirect effect. We estimate these effects in trial of insecticide-treated materials against the dengue mosquito vector, Aedes aegypti, in Venezuela, the endpoint being the Breteau index. We use a novel random effects Poisson spatial regression model. Spillover dependence is incorporated via an orthogonalized intrinsic conditional autoregression (ICAR) model. Spillover indirect effects are incorporated via the number of locations within a certain radius, set at 200m, that are in the intervention arm.

From the model with ICAR spatial dependence, and the degree of surroundedness, the intervention effect is estimated as 0.74—favouring the intervention—with a 95% credible interval of 0.34 to 1.69. The point estimates are stronger with increasing surroundedness within intervention locations.

In this trial there is some evidence of a spillover indirect effect of the intervention, with the Breteau index tending to be lower in locations which are more surrounded by locations in the intervention arm.

Item Type: Article
Subjects: QX Parasitology > Insects. Other Parasites > QX 525 Aedes
W General Medicine. Health Professions > W 20.5 Biomedical research
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
WC Communicable Diseases > Virus Diseases > Infectious Mononucleosis. Arbovirus Infections > WC 528 Dengue
Faculty: Department: Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI):
Depositing User: Stacy Murtagh
Date Deposited: 15 Sep 2020 10:16
Last Modified: 15 Sep 2020 10:16


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