Impact assessment of biolarvicides use in malaria control in a high transmission area in the Brazilian Amazon

Abstract

Malaria burden in Brazil has reached its lowest level in 35 years, with transmission virtually restricted to the Legal Amazon. In this context, the Brazilian Ministry of Health launched in November 2015 the Plan Malaria Elimination in Brazil. The focal nature of malaria in the country indicates that its elimination depends on the prioritization of controlling a small number of transmission. In the Vale do Juruá region, where 20% of malaria cases have been registered in Brazil, the establishment of artificial fish breeding sites was stimulated to increase local economic development. However, the precarious maintenance and abandonment of these fish ponds have been associated with the presence of Anopheles mosquitoes and consequently with the transmission of malaria in the region. The main challenge addressed in this project is the maintenance of high vector densities, especially due to the emergence of new artificial breeding sites, resulting from human action on the environment. Strategies of larval control of mosquitoes can be used as an effective tool in the integrated control of vectors for the reduction of malaria. The objective of this study is to evaluate the impact on the larval development of Anopheles spp. of two commercially available types of biolarvicides: VectoLex® (Bacillus sphaericus granular formulation - strain 2362), and VectomaxTM (granular formulation with the microparticle combination of the toxin produced by the Bacillus thuringiensis sub. Israelensis [strain AM65-52] and by Bacillus sphaericus [strain 2362]) - when aplied in fish ponds in the municipality of Rodrigues Alves (Acre). Most specifically it is intended to (a) evaluate the residual effect and retreatment intervals; (b) to develop a large-scale implementation strategy and (c) to analyze by microsatellite the genetic relationship between populations of larval and adult forms of Anopheles darlingi captured in the vicinity of participating households. Additionally, and in order to evaluate the impact on malaria transmission the prevalence of infection (before and after the intervention) in residents of 10 households located within a radius of 500 m around each breeding place will be assessed. It is expected to translate scientific evidence from the Brazilian Amazon into effective interventions for foci elimination of residual malaria transmission in Brazil. (AU)