A green path to dengue prevention

Traditional policies and programs, based on the use of larvicides and pesticices, have not managed to control the spread of the dengue virus and its vector, the Aedes mosquito. The trend in recent years has been towards strategies that incorporate some form of community participation, but before Camino Verde there was no hard evidence that community engagement actually had an impact on the disease.

In 2011-2012, the Centro de Investigación de Enfermedades Tropicales (CIET) and the University of California, Berkeley, along with local partners in both countries, conducted a study in Nicaragua and Mexico with the aim of assessing the efficiency of community mobilization for sustainable control of the Aedes mosquito. We call this initiative a Camino Verde —a Green Path— to dengue prevention. Three kinds of evidence (see next section) provided the basis for community mobilisation as well as for measuring the results, We gathered this evidence from a panel of urban and rural communities and compared the results from the half of those communities where the mobilisation activities took place (those we label “intervention”) with the other half (which we label “control”) where the intervention was not carried out.

This kind of comparative study is called a cluster randomised controlled trial, because the sites or clusters are randomly assigned to the intervention or control groups, balanced according to the area and children’s entomological and immunological status. Some hundred thousand people participated in the intervention across the two countries. The trial was financed by the UBS Optimus Foundation.

The results of the Camino Verde trial were published in the BMJ (British Medical Journal) in July 2015:  http://bmj.com/cgi/content/full/bmj.h3267.

Evidence for action

This trial applied lessons learned from a 2004-2007 pilot exercise in Nicaragua that tested the whole idea of community  mobilisation for dengue control. The kingpin of this approach is an informed dialogue with community members based on their own evidence. The evidence includes:

  • Data from the baseline surveys about the communities’ knowledge and attitudes towards the threat, what they were doing and spending to try to prevent it and what it was costing them when a family member got sick;
  • Results of entomological surveys that identify Aedes larvae and pupae in participants’ households;
  • Serological evidence of dengue virus infection in children, obtained by analysing the change in dengue virus-specific antibody levels in the children’s saliva.

These data were not only used to measure the impact of an intervention, but were given back to the community through house visits and focus groups to catalyse and direct informed action. We call this process Socialization of Evidence for Participatory Action (SEPA). It is a method for communicating evidence that CIET has applied in various projects and different countries.

Small local community research and action teams (which we call “brigadas”) in Mexico and Nicaragua received training in pesticide-free vector control. This intervention started with returning to each household to feed back the survey results, including those from the saliva samples, to its members. Key community informants were contacted and a series of discussion groups were organised with community leaders, adult citizens, teachers and children. Brigadistas visited every household to explain the dengue threat and the life-cycle of the Aedes mosquito and to accompany householders as they examined all water receptacles on the property for the presence of mosquito larvae and pupae. Brigadistas also helped to organise community-wide activities, events and publicity to raise consciousness about dengue and how to control it.

In 2012-13, we measured changes in immunological state and the presence of pupae and larvae, both in the intervention and control sites.