New entomological and virological data on the vectors of sylvatic fever in Brazil

ABSTRACT

The present report focuses on recent ecoepidemiological data on yellow fever, obtained recently in two very distinct ecoepidemiological contexts the Barcarena (PA) area, situated in the dense Amazonian rain forest, and the Campo Grande (MS) region, situated in the cerrado with gallery forest in central Brazil. In the first region, one strain was isolated from a pool of 6 Haemagogus janthinomys. In the other region, 2,480 anthropophilous mosquitoes were collected, of which near 40 per cent were potential YF vectors. These species, classified by decreasing relative abundance, were Aedes scapularis, Sabethes chloropterus, Hg.janthinomys, Hg. leucocelaenus, Hg. spegazinii, and Sa. soperi. Four strains of YF virus were isolated from Hg. janthinomys, one from Sa. cheoropterus (first report for South America) and one from Sa. soperi (first report). The minimal infection rates varied among the three localities of collection but were all high, compared with previous data. The mean daily survival rate was O.9635 for the populations of Hg. janthinomys, allowing extrapolation of the value of the infection rate when people were infected most recently. It was deduced that the epizootics were intense and more or less concomitant in the three areas. The main problem that remained to be solved concerns the mode(s) of reintroduction or survival of YF virus in each of the two regions under study.