RESUMO
Two groups of teneral flies (aged less than 32 hours) of Glossina morsitans morsitans (Mall) were fed separately on two rats that had been infected with Trypanosoma (Nannomonas) congolense IL 1180, among which one had a low parasitaemia (antilog 5.4-5.7) and the other a high parasitaemia (antilog 7.8-8.1). Following to the two modes of parasitaemia, variations of the procyclic indexes were found between males and females. When both sexes were considered, it was found that the intestinal infection rate was relatively higher in the flies that were fed on the rat with a low parasitaemia than in those fed on the rat with a high parasitaemia. Although no significant differences in metacyclic indexes were observed between sexes, the mature infection rate was most pronounced in the flies that were fed on the rat with high parasitaemia. When both sexes were considered, the vectorial competence (VC) reached 0.5532 and 0.5521 in the flies that had been fed on the rats with low and high parasitaemia, respectively. The VC of the two modes of infectious feeding was not significantly different. However, when considering the parasitaemia of antilog 5.4-5.7, the VC was relatively more important in the females than in the males. No significant difference in VC was detected between sexes when considering the antilog 7.8-8.1 parasitaemia. It was found that there is discrepancy in the way the metacyclic infection and the VC evolve in relation to the procyclic infection, suggesting that the intensity of the parasitaemia only influences the intestinal stage.
