Avaliação das flutuações naturais da densidade da população dos vectores da esquistossomiase no vale do Infulene

Abstract

In order to obtain information about the population dynamics of schistosomiasis vectors in the Infulene valley, the vector species were identified and the natural fluctuations of their density were evaluated. The study was carried out for six months and the sampling began in October 1994 and ended in April 1995. Along the valley, four ditches were chosen with the designation Ml, M2 (old ditches) and N1, N2 ("new" ditches). In these ditches, three sites with a spacing of 50 m were marked and it is in these sites that the samples were collected. The results show that in the valley there is a Bulinus (Physopsis) spp group with two species Bulinus (P) africanus and Bulinus (P) globosus both vectors of S. haematobium and one species Biomphalaria pfeifferi vector of S. mansoni. The density of these species shows periodic fluctuations, but in general they tend to increase in the beginning of the hot and rainy season. In the M1 and M2 ditches the density of Bulinus (P) spp varies from 7.2 to 52.5 (molluscs/reddish) and in the N1 and N2 it varies from 0.1 to 54 (molluscs/redded). In ditches N1 and N2 the density equivalent to the initial of ditches M1 and M2 is reached in the fourth and eighth period respectively. The density of B. pfeifferi ranges from 0 to 27.8 and 0 to 0.8 in trenches M1, M2 and N1, N2 respectively. These species reproduce throughout the hot and rainy season. But there are times when the reproduction rate is relatively high. In the Bulinus (P) spp group there are two with a high rate and one with an intermediate rate. The first in September and early October; the second in February and the intermediate beginning of January. At Biomphalaria pfeifferi, there are two, the first from September to October, the second in December. Bulinus (P) spp presented a total infestation rate per period varying from 0 to 2.1% with the maximum percentage registered in the months of November and December and 0% for Biomphalaria pfeifferi. (TRADUÇÃO NOSSA)