Study of potential vectors and ecological factors associated with the emergence and circulation of yellow fever in Brazil

Abstract

The Yellow Fever (YF) in Brazil and in other South countries was basically restricted to the wild cycle, being mainly carried by mosquitoes of the genera Haemagogus and Sabethes. Epizootic outbreaks of this disease in non-human primates have been recorded with some periodicity, which can vary from five to ten years, preceding the emergence of human cases in surrounding rural areas. In the last two decades there has been a change in the epidemiological standard of the FA in Brazil, because most of the cases have been recorded outside the North and Midwest regions, considered areas of natural outbreaks of the disease. The most recent outbreak has provoked an expressive number of epizootic diseases and human cases in the southeastern region of the country, including notifications in areas previously considered free of YF, the example of the metropolitan region of Sao Paulo. There is a great concern with a possible re-introduction of YF in urban areas of the country, especially in densely populated regions and with low vaccination coverage. Despite the effort that has been undertaken by the health agencies for the surveillance and immunization of populations in areas of risk, there are still unclear questions about how epizootic waves and epidemics of this disease propagate and why they run at intervals more or less regular in the Extra-Amazon region. This proposal aims to develop studies that seek to understand, in an integrated way, which environmental and biological factors favor the emergence of epizootic diseases and epidemics of YF and its dispersion by non-endemic areas of Brazil, as well as develop models that help Explain and predict the dynamics of circulation of the virus in the Extra-Amazon region. The work areas will cover four pre-defined macro according to their role in the emergence and circulation of the virus, starting from the endemic region and following a circulation corridor to the southeast region of the country. In each macro will be selected areas with prior history of animal diseases in primates or human cases for the collection of adult mosquitoes, with emphasis on species considered to be virus transmitters. Throughout the research the following studies will be developed: Identification of preferred hosts through the study of feeding habit of vectors; Population genomics and landscape influence on the genomic signature of vectors; Influence of landscape and climate on the presence and abundance of vectors and in the distribution of epizootic diseases and human cases of yellow fever; Niche modeling for vectors and hosts; Theoretical models for the dynamics of transmission and dispersion of the YF during epizootic waves. This proposal is expected to elucidate issues not yet clarified on the circulation patterns of the YF virus in Brazil and the risk of its re-introduction into urban areas. From the information generated, it will be possible to predict and anticipate future risk situations, enabling the implementation of more effective surveillance systems, focused on the main factors influencing the spread of emerging virus lineages to the not endemic regions of the country, as well as a better allocation of resources during vaccination campaigns. (AU)