[Vectorial competence of non-teneral Glossina morsitans morsitans (Mall strain) flies infected by Trypanosoma (Nannomonas) congolense IL 1180]. / Compétence vectorielle des mouches non ténérales de Glossina morsitans morsitans (Souche Mall) infectées par Trypanosoma (Nannomonas) congolense IL 1180.

Non-teneral tsetse flies of Glossina morsitans morsitans (strain Mall) about 16 days old were fed, once, on a rat infected by Trypanosoma congolense IL 1180. The global vectorial competence (VC) of these flies was appraised at 0.1035. VC in males was more important than for females. Infection by mesoprocyclic index was greater in female flies than in male ones, whereas for metacyclic index the reverse was true. This work shows that the age limits, but does not impede metacyclogenesis of non-teneral tsetse flies of G. m. morsitans (strain Mall).

[Effect of the number of health meals before an infectious meal on the vectorial competence of Glossina morsitans morsitans infected by Trypanosoma congolense IL 1180]. / Influence du nombre de repas sains antérieurs au repas infectieux sur la compétence vectorielle de Glossina morsitans morsitans infectée par Trypanosoma congolense IL 1180.

The purpose of this work was to assess the influence of several healthy meals (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 those from group C were given two consecutive healthy meals on days 1 and 2. All the flies were experimentally infected with Trypanosoma congolense IL 1180 when the maximum age reached 32 h for flies with no meal, 56 h for those 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 were 0.99 +/- 0.01, 0.96 +/- 0.02 and 0.95 +/- 0.03. Considering the flies which were fed one healthy meal, the respective values were 0.42 +/- 0.13, 0.50 +/- 0.01 and 0.21 +/- 0.06, whereas the values for the flies receiving two healthy meals were 0.45 +/- 0.11, 0.29 +/- 0.19 and 0.13 +/- 0.05. The meso-procyclic and metacyclic indexes as well as the VC in both sexes were more 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 not show any significant differences between the flies fed one or two healthy meals, whereas the metacyclic index of male flies which received one healthy meal was significantly higher than those fed two healthy meals. These results 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.

[Effect of the intensity of host parasitemia on the vectorial competence of Glossina morsitans Westwood, 1850 (Mall) infected by Trypanosoma (Nannonmonas) congolense IL 1180]. / Influence de l'intensité de la parasitémie de l'hôte sur la compétence vectorielle de Glossina morsitans morsitans Westwood, 1850 (Mall) infectee par Trypanosoma (Nannomonas) congolense IL 1180.

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.

[Vectorial competence of Glossina tachinoides Westwood and Glossina palpalis gambiensis Vanderplank infected by Trypanosoma brucei brucei EATRO 1125]. / Compétence vectorielle des Glossina tachinoides Westwood et Glossina palpalis gambiensis Vanderplank infectées simultanément par Trypanosoma brucei brucei EATRO 1125.

The vectorial competence (VC) of teneral (less than 32 h) Glossina tachinoides Westwood and G. palpalis gambiensis Vanderplank, fed simultaneously on a guinea-pig infected with Trypanosoma brucei brucei EATRO 1125, was assessed. Statistical analysis of the experimental results revealed that female G. tachinoides had a significantly higher midgut infection rate than males. Such a sex-related difference was not observed in G. p. gambiensis. Male G. p. gambiensis had higher midgut infection rates than male G. tachinoides. The metacyclic index did not differ between both subspecies, although G. p. gambiensis showed relatively more metacyclic infections than G. tachinoides. A global VC of 0.0242 and 0.0483 was found for G. tachinoides and G. p. gambiensis, respectively. VC did not differ significantly either between sexes or between the two species. However, G. tachinoides more rapidly infected the feeding host than G. p. gambiensis. In all infected flies, the procyclic index value was superior to the metacylic index value, suggesting that the infection is established by an ascending origin. Both large and slender parts of the salivary glands were constantly infected. Longitudinally dividing trypomastigotes of unequal length have been observed in the alimentary canal of the flies.

[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.

Prophylactic effects of isometamidium- and ethidium-sustained release devices against Trypanosoma congolense in cattle.

Two successive experiments were carried out in which three cows were treated by intramuscular injection of either 0.5 mg/kg isometamidium or 1 mg/kg ethidium and compared with another group of three cows which received a subcutaneously implanted sustained release device (SRD) containing the same dose of drug. The prophylactic effect of both drug formulations was evaluated by exposing the animals at monthly intervals to Glossina morsitans morsitans infected with Trypanosoma congolense. The average protection period using the isometamidium- and the ethidium-SRD was extended by a factor of 3.2 and 2.8, respectively in comparison with the intramuscular injection of the drugs. In the analysis of isometamidium concentrations in the serum of the animals using a competitive drug-ELISA the drugs remained present for much longer periods in the sera of the implanted animals than in those of the intramuscularly treated cattle. The animals were still protected, however, a long time after the disappearance of detectable drug levels in the serum. No difference in drug sensitivity could be observed, when breakthrough isolates were compared from animals which received the ethidium-SRD and those treated intramuscularly, although a slight loss sensitivity occurred in the breakthrough isolates as compared to the parent trypanosome population.

[Experimental infection of Glossina morsitans morsitans (Mall) with Trypanosoma congolense (ZRE/G143/90). Parasite cycle and vector competence in the tsetse fly]. / Infection expérimentale de Glossina morsitans morsitans (Mall) par Trypanosoma congolense (ZRE/G143/90). Cycle du parasite et competence vectorielle de la glossine.

This report presents an experimental study of the life cycle of Trypanosoma congolense (ZRE/G 143/90) in relation to the vectorial competence of Glossina morsitans (Mall). The rate of engorgement at the time of an infectious meal and the mortality before day 15 of the life cycle were not significantly different between male and female flies. The mesocyclic forms of trypanosomes were regularly observed in the proventriculus, crop duct, oesophagus, cibarium and proboscis, except in the crop. On day 12 of the cycle, epimastigote forms were predominant in the proboscis. On day 13 of metacyclogenesis, four out of six rats (67%) used for feeding the flies were positive for trypanosomes upon buffy coat examination. These results demonstrate the short incubation period of trypanosomes in the vertebrate host and precociousness of the vectorial competence of some individuals of G m morsitans (Mall). Among the three cyclic stages, only the procyclic forms in the intestine showed a significant difference between the sexes, the male flies being more infected than the females. Metacyclogenesis undergoes three cleavages leading to the successive and permanent establishment of the procyclic, mesocyclic and metacyclic forms in the midgut, proventriculus and proboscis respectively.

[Standardization and evaluation of a manual salivation method for the detection of Trypanosoma infection in the tsetse fly (Diptera: Glossinidae)]. / Standardisation et évaluation de la technique de salivation manuelle pour le dépistage des infections par trypanosomes chez la glossine (Diptera: Glossinidae).

Two methods of salivation of tsetse flies, namely manual salivation and method of Bruce et al. were simultaneously evaluated on 1,702 male uninfected Glossina palpalis palpalis (Zaire), G. palpalis gambiensis (Bobo-Dioulasso), G. p. gambiensis (Maisons-Alfort) et G. morsitans morsitans (Mall) fasted for 23, 48 and 72 hours. The risk of salivation was 0.66 by the manual method and 0.01 by the method of Bruce et al. The manual salivation method was standardised on 79 male G. m. morsitans (Mall) infected with Trypanosoma congolense IL 1180. By this method, 70.88% of flies carrying mature and/or immature infection were identified. A clear difference was observed in the proportion of tsetse flies which salivated after 72 hours and those which salivated after 48 and 24 hours of fasting.

[Vectorial capacity of Glossina palpalis gambiensis (Bobo Dioulasso) for Trypanosoma brucei brucei EATRO 1125]. / Etude de la capacité vectorielle de Glossina palpalis gambiensis (Bobo Dioulasso) vis-à-vis de Trypanosoma brucei brucei EATRO 1125.

A total of 440 teneral Glossina palpalis gambiensis received one single bloodmeal on a guinea pig infected chronically with Trypanosoma brucei brucei EATRO 1125. Metacyclic infections were present in 11.29% of the flies, in 2.32% infections were limited to procyclical stages. No significant difference in vectorial capacity was observed between male and female flies, the level of metacyclic infections being 13.19% in the former and 9.55% in the latter. The parasitaemia level, the percentage of stumpy forms at the moment of the blood meal and the maintenance conditions of the flies seemed to influence the infection of the flies.