Spatial repellents

Full Title Spatial repellents as alternatives to DDT.

Short Title

Project Leader Sarah Moore

Description The effectiveness of any vector control intervention depends on four factors: 1) unit efficacy i.e. the number of people protected per unit resource outlay, 2) the duration of that protection, 3) community acceptance and uptake, 4) individual, community or programmatic adherence. The most effective technologies protect large numbers of people for a long time at a realistically affordable price. For this reason we propose to focus on household protection rather than personal protection to increase the number of people protected per unit from an average of 1 or 2, to 5 or 6. In order to be effective for public health use, interventions must also provide a community-level protection against disease vectors that goes beyond the coverage of individuals and houses and even protects those immediately outside of houses and non-users. Additionally, a practical vector control intervention should be simple and non-invasive, requiring little investment or effort from the end-users. The health benefits of household protection measures are several-fold. If applied in a careful manner they can continuously protect all household members from multiple vector species at all times, day or night.

One such intervention that may fulfil all of the above criteria is a spatial repellent. These compounds evaporate into the air where they affect insects’ behaviour and prevent them reaching their target (in this case all the people within the house, and possibly the near vicinity of the house). By applying them in a way that allows continuous evaporation, they will provide protection during both day and night, in contrast to bednets that work only at night while people are in bed. There is evidence that spatial repellents could exert their effect over several feet, so they may be applied to the points of entry of a house, effectively closing the household to insects without blocking it off physically. This is a very important factor in warm tropical climates where ventilation is important to householders and where houses are often of too poor a quality to seal effectively with physical barriers such as netting. Much of the household activity in rural Africa occurs in front of the home (cooking, eating, and socializing), so a repellent working over a few feet has the potential to protect even when people are not indoors. Also, spatial repellents will substantially benefit the community through increased vector mortality by forcing them to spend longer periods of time searching for resources (food and shelter). Spatial repellents may therefore offer enhanced personal and communal protection which is independent of housing quality, with minimum end-user effort and discomfort.

Thus, the objectives of this project are;

1. Develop rigorous systems for comparing the key actions of DDT in comparison with existing alternatives in experimental huts.

2. Evaluate optimal insecticide and delivery format combinations across a range of active ingredient dosages so that the interaction between efficacy, product lifetime and cost are fully understood

3. Assess desirable characteristics of spatial repellent products among African and Western users and industrial decision makers.

Collaborators Gerry Killeen               Ifakara Health Institute

Raphael N'Guessan       Liverpool School of Tropical Medicine

Ann Kelly                   Ifakara Health Institute

John Grieco                 Uniformed Services University of the Health Sciences

Nicole Achee               Uniformed Services University of the Health Sciences

Mark Rowland              Liverpool School of Tropical Medicine

Greg Devine                Biotechnology & Biological Sciences Research Council

Martin Akogbéto Codjo  Centre de Recherche Entomologique de Cotonou

Source of funding Bill & Melinda Gates Foundation

Start Date November 2009              End Date   May 2012

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