The influence of a healthy meal prior to an infectious meal on the vectorial competence of Glossina morsitans morsitans infected by Trypanosoma congolense IL 1180.

The purpose of this work was to assess the influence of several healthy mea ls (0, 1 and 2) prior to the infectious one on the vectorial competence of Glossina morsitans morsitans (Mall). The teneral flies (< 32 h old) of this line were divided into three groups. The tsetse flies of group A received no meal. The ones of group B received one healthy meal on day 1, whereas th ose from group C were given two consecutive healthy meals on days 1 and 2. All the flies were experimentally infected with Trypanosoma congolense IL 1 180 when the maximum age reached 32 h for flies with no meal, 56 h for thos e with one healthy meal and 80 h for those who received two healthy meals. When both sexes were considered, the meso-procyclic and metacyclic indexes as well as the vectorial competence (VC) of the flies receiving no meal wer e 0.99 +/- 0.01, 0.96 +/- 0.02 and 0.95 +/- 0.03. Considering the flies whi ch were fed one healthy meal, the respective values were 0.42 +/- 0.13, 0.5 0 +/- 0.01 and 0.21 +/- 0.06, whereas the values for the flies receiving tw o healthy meals were 0.45 +/- 0.11, 0.29 +/- 0.19 and 0.13 +/- 0.05. The me so-procyclic and metacyclic indexes as well as the VC in both sexes were mo re important in the flies which received no meal than those fed with one or two healthy meals. The meso-procyclic and metacyclic indexes and VC did no t show any significant differences between the flies fed one or two healthy meals, whereas the metacyclic index of male flies which received one healt hy meal was significantly higher than those fed two healthy meals. These re sults indicate that the number of non-infected (healthy) meals prior to an infected meal reduces the interaction between G. m. morsitans infected and T. congolense. (C) Inra/Elsevier, Paris.