[Vectorial competence of Glossina palpalis palpalis, Glossina p. gambiensis and Glossina morsitans morsitans flies for a clone of Trypanosoma (Nannomonas) congolense IL 1180]. / Compétence vectorielle des mouches de Glossina palpalis palpalis, G.p. gambiensis et Glossina morsitans morsitans vis-à-vis d'un clone de Trypanosoma (Nannomonas) congolense IL 1180.

The authors report on the results of experimental infections of teneral (age < 32 hours) and non-teneral (age between 80 and 96 hours) Glossina palpalis palpalis, G. p. gambiensis and G. morsitans morsitans with Trypanosoma congolense IL 1180. Flies were infected once on a parasitaemic rat. Teneral flies, both sexes indiscriminate, showed a procyclic and metacyclic infection rate respectively of 0.0588 and 0.7272 for G. p. palpalis; 0.0525 and 0.0416 for G. p. gambiensis; 0.6493 and 0.7300 for G. m. morsitans. Neither of the non-teneral G. palpalis subspecies had any vectorial competence, whereas G. m. morsitans had procyclic and metacyclic infection rates of 0.4541 and 0.7884. Statistical analysis could not demonstrate any significant difference in metacyclic infection rate between teneral and non-teneral G. m. morsitans. Teneral flies of each subspecies transmitted the infection to rats, used as hosts, before the twentieth day. Concerning trypanosome development in the fly, it was observed that five days after infection procyclic and mesocyclic forms could be observed simultaneously in all flies dissected at that moment.

Effect of the life-span of female Glossina palpalis gambiensis on the weight and size of its progeny.

Pupae and teneral flies of Glossina palpalis gambiensis originating from three successive reproductive cycles were compared for their size and weight. In general, pupal weight and fly weight increased, whereas fly size, measured as wing vein length, decreased with the number of reproductive cycles. The linear regression observed between weight and wing vein length of the fly demonstrated that, particularly for flies originating from the first and second larvipositions, small changes in wing vein length reflected substantial differences in weight. The results of these laboratory experiments were compared with some field data on Glossina morsitans from Zambia and related literature. The life span of the female tsetse, affecting the size of her progeny, could clarify partially some of the field observed seasonal changes in size, whereas the correlation between fly size and weight could eventually explain the differential mortality of some size classes of tsetse flies. However, whether these laboratory observations can be extrapolated to the field has still to be confirmed.