Geospatial methods for investigating Plasmodium vivax reservoirs in rural Brazilian Amazon

Abstract

The intensification of malaria control activities in the late 1990s led to a reduction in transmission; still, about 260,000 new cases were reported in 2012, 99.9% of them in the Amazon. Transmission is most intense in mining sites, logging areas, and agricultural settlements. About 85% of the infections are caused by Plasmodium vivax, indicating that difficulties in controlling this species may contribute to the maintenance of malaria transmission. Current malaria control strategies in Brazil are based on early diagnosis and treatment of clinical cases. However, an important gap in the research agenda corresponds to effective strategies for identifying and treating asymptomatic reservoirs of infection, especially in areas with low malaria incidence that reach a pre-elimination phase. This topic will be covered during the stay of Prof. Marcia Castro, with a special focus on the use of geospatial techniques. Marcia Castro will apply geospatial methodologies, combining remote sensing, geographic information systems and spatial statistical analysis. These techniques will be integrated with the activities of the research project "Prospects for elimination of residual malaria in the Brazilian rural Amazon: strategy to target reservoirs of P. vivax", coordinated by Prof. Marcelo U. Ferreira. The project aims to implement and evaluate a strategy to detect symptomatic and asymptomatic carriers of the parasite (potential reservoirs of infection) in areas of residual malaria transmission, focused on monitoring potential foci of transmission around confirmed clinical episodes (index cases). The foci of transmission are defined as areas surrounding index cases, and the study is being done in Acrelândia, Acre. The use of geospatial techniques brings three significant contributions to the project: (i) the analysis of high resolution satellite images allows the accurate identification of the area in the neighborhood of an index case; (ii) the mapping of index cases allows the assessment of spatial and temporal clustering, and (iii) spatial statistical techniques facilitate the analysis of optimal radius to be considered for the definition of the area surrounding the index case, as well as an integrated monitoring strategy combining molecular and epidemiological data. The visiting researcher will not participate in laboratory experiments or handle biological samples. Her participation include the analysis of data collected by the project (mapping and spatial analysis of information), the interpretation of high-resolution satellite imagery (whose results will allow a more precise definition of the areas to be defined as a potential source of transmission), and the integration of molecular and epidemiological findings in a spatial framework. Results of the project will facilitate the proposal of a strategy to identify reservoirs of P. vivax that could be considered by the Ministry of Health. During her four-month stay, Marcia Castro will focus her activities on the mapping of information being collected in Acrelândia, searching for patterns of temporal and spatial clustering (based on clinical cases and molecular analysis), interpretation of satellite imagery in order to properly define the foci of transmission, and spatial modeling of integrated data. In addition to research activities, Marcia Castro will participate as a speaker in the discipline "Molecular epidemiology of infectious and parasitic diseases" - BMP5756 taught by Marcelo U. Ferreira. (AU)