Contribution to the study of the ejection of Trypanosoma congolense by Glossina morsitans morsitans (Diptera, Glossinidae) in the laboratory

Abstract

The process of trypanosome ejection was studied in Glossina morsitans morsitans experimentally infected with Trypanosoma congolense EATRO 325 (Savannah type). The technique used was that of salivation on warm slides (38°C) for 5 minutes. The effect of various media (PSG, blood, PSG + ATP) was evaluated. Whatever the sex of the flies, the percentages of infections revealed by this technique do not differ significantly using either PSG or blood. Detection of parasites by microscopic examination of saliva showed that 75 to 100 % of the males eject trypanosomes during successive probes, whereas 30 to 100 % of the females were found to be positive using the same procedure. The number of trypanosomes ejected per fly varied greatly in the course of time, with an average of 48.4 (of which 32.5 were infective metatrypanosomes) among the males and 19.3 (of which 12.2 were infective metatrypanosomes) among the females, with an increasing proportion of stumpy forms. Addition of ATP did not affect the proportion of flies found positive, but seemed to favour the ejection of trypanosomes notably stumpy infectant forms. These results are discussed by comparing the aspects of the vector-parasite relationships and the vectorial capacity of G. morsitans morsitans with a parasite belonging to the subgenus Nannomonas.