Camino Verde in Mexico

Brigadistas explain the different stages of the mosquito’s life cycle during a visit to an Acapulco household.

There were several causes for the search of a “green path” towards dengue control in Guerrero State. The spread of dengue to rural areas and the increase in cases of dengue fever and dengue hemorrhagic fever meant the failure of traditional strategies to control the disease through the use of chemicals. Various studies carried out by CIET since 1988 show that the population doesn’t have adequate knowledge to prevent the vector mosquito’s reproduction.

At the same time, a CIET study in Nicaragua recorded an alternative experience through evidence/based community mobilisation. The pilot project showed the feasibility of a “green path” towards vector control, with substantial gains for the intervention communities.

Based on these facts, and with the participation of the Guerrero health authorities (Secretaría de Salud de Guerrero), residents and collaborating partners, we initiated a cluster randomised controlled trial across the entire Pacific coast of Mexico’s southwestern state of Guerrero, subdivided into the Acapulco (850 thousand inhabitants), Costa Chica (385 thousand inhabitants) and Costa Grande (450 thousand inhabitants) regions. Our goal was to show that community mobilisation based on local evidence is no less effective than chemical products in reducing the number of breeding-sites, the larvae and pupae rates and the Aedes mosquito density. Specifically, the trial sought to reduce dengue risk through:

  1. a)   repeated cycles of dissemination and discussion of community entomological and serological evidence, knowledge gaps, attitudes and actions;
  2. b)   evidence-based community vector control interventions, including group discussions of the results, repeated household visits, school activities and community events;
  3. c)   intervention impact measurement at the end of the trial.

One of our explicit aims was to develop a sustainable community strategy for vector control that will reduce the need to use pesticides. We also seek to prove that this strategy has other health related advantages, such as an increase in communities’ social capital.

The process at work

The Camino Verde intervention components were spaced out between 2009 and 2012. The first step consisted in a baseline study to determine the entomological and immunological ecosystem, as well as the knowledge, attitudes and behaviours related to dengue. Based on the latest census (2008), we randomly selected 90 clusters, stratified by area in Acapulco and municipality in Costa Grande and Costa Chica. We recorded Aedes aegypti breeding sites in these locations, carried out a larvae and pupae count and estimated new infections based on children’s saliva samples. At the same time, we sought to establish knowledge, attitudes, practices and other cognitive and behavioural variables based on CIET’s CASCADA model.

Afterwards, the 90 clusters were randomised into intervention (45) or control (45), balanced by cluster size; household entomological rates; general population disease rates; recent disease and infection rates among children 3 to 9 years old, measured through saliva samples; and children’s immunological status. The intervention involved the socialisation of study results in each household, focus groups and different community spaces, with community members’ leadership and participation, which we call socialising evidence for participatory action (SEPA). Facilitators and brigadistas play a key role in this process. Peer-to-peer monitoring is also carried out among the different communities.

These actions sought to provide information to communities about their entomological and serological status and provide the evidence for mobilising the communities to adopt measures such as cleaning and sealing water tanks.

In the second half of 2012 we conducted a second round of measurements in the intervention and control sites  to assess the changes in infection rates among children, household larva rates and the CASCADA components.