Larval source reduction with a purpose: Designing and evaluating a household- and school-based intervention in coastal Kenya

Background

Since Aedes aegypti mosquitoes preferentially breed in domestic containers, control efforts focus on larval source reduction. Our objectives were to design and test the effectiveness of a source reduction intervention to improve caregiver knowledge and behaviors in coastal Kenya.

Methodology/Principal findings

We conducted a cluster-randomized controlled trial with 261 households from 5 control villages and 259 households from 5 intervention villages. From each household, one child (10–16 years old) and his or her primary caregiver participated in the intervention. We assessed caregiver knowledge and behavior at baseline, as well as 3 and 12 months after the intervention. We assessed household entomological indices at baseline and 12 months after the intervention to avoid seasonal interference. We conducted qualitative interviews with 34 caregivers to understand barriers and facilitators to change. We counted and weighed containers collected by children and parents during a community container clean-up and recycling event. After 12 months, caregiver knowledge about and self-reported behavior related to at least one source reduction technique was more than 50 percentage points higher in the intervention compared to control arm (adjusted risk differences for knowledge: 0.69, 95% CI [0.56 to 0.82], and behavior: 0.58 [0.43 to 0.73]). Respondents stated that other family members’ actions were the primary barriers to proper container management. The number of containers at households did not differ significantly across arms even though children and parents collected 17,200 containers (1 ton of plastics) which were used to planted 4,000 native trees as part of the community event.

Conclusions/Significance

Our study demonstrates that source reduction interventions can be effective if designed with an understanding of the social and entomological context. Further, source reduction is not an individual issue, but rather a social/communal issue, requiring the participation of other household and community members to be sustained.

The disease burden of arboviruses transmitted by Aedes aegypti mosquitoes remains high globally. Since these mosquitoes are day-biters, bed nets are not effective at preventing mosquito bites. Additionally, because Ae. aegypti preferentially breed in domestic containers, control efforts focus on reducing containers for mosquito breeding (source reduction). We developed and evaluated a household- and school-based intervention to improve knowledge and behaviors related to source reduction. We assessed caregiver knowledge and behavior before the intervention and after 3 and 12 months. Subsequently, we conducted qualitative interviews among a sub-set of participants to understand why they did or did not change their behavior. We also assessed mosquito-related indices: the number of breeding containers and immature mosquito abundance before and 12 months after the intervention. We found that those receiving the intervention had more knowledge and self-reported behavior change than those who did not. Nonetheless, the intervention had no effect on mosquito nor containers abundance. In a multi-person household, all household members need to be committed to change, not just the caregiver and child. Our study highlights how mosquito control is not an individual issue, but one that needs the participation of a sufficient majority of household and community members to ensure effectiveness.