A febre amarela na Africa e na América do sul

• Autor(a) principal: Dégallier, Nicolas
• Data de Publicação: 1994
• Outros Autores: Rosa, Amélia Paes de Andrade Travassos da, Herve, Jean-Pierre, Rosa, Jorge Fernando Soares Travassos da, Vasconcelos, Pedro Fernando da Costa, Barros, Vera Lúcia Reis Souza de, Dias, Leônidas Braga, Rosa, Elizabeth Salbé Travassos da, Rodrigues, Sueli Guerreiro
• Tipo de documento: Artigo de conferência
• Idioma: por
• Título da fonte: Repositório Digital do Instituto Evandro Chagas (Patuá)
• Texto Completo: https://patua.iec.gov.br/handle/iec/6786
• topic: Febre Amarela; Vírus da Febre Amarela / isolamento & purificação; Congressos como Assunto; Resumo de Reunião; Africa; America do Sul

In order to look for na eco-epidemiological modelo f sylvatic yellow fever (YF) transmission in South America, differences and similarities to African YF are considered from available data. Strains from both areas, representing various topotypes, are distinct serologically, genetically and biochemically. Many ecological differences also exist. In Africa, all vector mosquitoes are Aedes species, some related to the forest cycle (Ae. Africanus group) and others responsible for the transmission in dryer areas (Ae. Luteocephalus, Ae furcifer group). In Central Africa, the tick Amblyomma variegatum has been found naturally infected by YF virus but the real importance of this fact remains unknown. In South America, and particularly in Brazil, the only vectors are species of Haemagogus, an indigenous neotropical genus. The species Hg. Albomaculatus has been incriminated in human peridomestic transmission in central Amazônia (Western Pará State). On the two continents, monkeys are the only regular vertebrate hosts of YF but the indigenous neotropical monkeys, seem to be more susceptible to infection, resulting in higher mortalities. In South America some arboreal marsupials (Didelphidae) may play some as yet unconfirmed role in sylvatic maintenance of the virus. Ecological differences are also noted. The South American and African vectors are diurnal and crepuscular/nocturnal in habits, respectively. The urban vector (Ae. Aegypti) has the same habits in both continents, but its competence in transmitting the virus is very variable, and no urban epidemic has been notified in South America since the ‘40’s. A general eco epidemiological model has been elaborated to explain the maintenance and circulation of YF in west and Central Africa, which is related to phytogeographical regions. Because no such hypothesis has yet been presented in the case of YF in South America, we tested this with the available data from Brazil. All confirmed occurrences (386, by isolations or serological and histopathological diagnosis: table 1) were distributed according to five phytogeographical zones: dense rainy forest (189), open rainy forest (30), savannah with gallery forest (147), ecotones (10) and decidual seasonal forest (7) (figs. 1, 2). For each of these zones mean intervals between years with occurrences of YF were estimated. They were all found lower than 3 years, and lower than 5 years when standard deviation was added (fig. 3). Despite the close values obtained for means, the distribution of the years as a function of number of occurrences of YF showed two groups (fig. 4): (a) gallery forest and dense forest and (b) open forest and ecotones. However, more data are needed to study such variation, which are thought to be related to ecological differences in YF transmission. Finally, evolutionary aspects are evoked with more sound arguments in favour of an old vicariance model of evolution of YF in Africa and South America. Absence of YF in Asia is probably related to the presence of other Flaviviruses occupying the same ecological niche.