[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.

Extension of the prophylactic effect of isometamidium against trypanosome infections in cattle using a biodegradable copolymer.

Two trials were carried out in order to compare the prophylactic effect of a subcutaneously implanted sustained release device (SRD) containing a mixture of a biodegradable copolymer, poly(caprolactone-co-L-lactide), and isometamidium (ISMM) with that obtained after intramuscular injection of the drug. In a first experiment under controlled conditions, two groups of cattle were treated with 0.5 mg/kg isometamidium either as a SRD or intramuscularly (i.m.), and exposed at monthly intervals to Glossina morsitans morsitans infected with Trypanosoma congolense. The average protection period was at least 24 months in the SRD treated against 5.7 months in the i.m. treated group. Using an ISMM enzyme-linked immunosorbent assay, the drug could be detected until 140 days post-treatment in the latter group, whereas in the former group, traces of the drug were detectable until 330 days after treatment. Furthermore, a field trial was carried out at the Madina Diassa ranch in Mali involving three groups of N'Dama cattle, each containing 23 or 24 animals. Two groups were treated with 1 mg/kg ISMM either as a SRD or i.m. and a third group served as untreated control. Twelve months after treatment, the cumulative infection rates were 56.5, 87.8 and 91.6% in the SRD implanted, the i.m. treated and the control groups, respectively. The ISMM concentrations were slightly lower than in the laboratory trial, but the overall pattern of drug disappearance from the sera of the SRD treated cattle was very similar in both trials. Statistical analysis showed that the incidence of trypanosomiasis was significantly lower in the SRD treated than in the i.m. treated group.

[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.

Biodegradable polyesters for controlled release of trypanocidal drugs: in vitro and in vivo studies.

Copolymers of epsilon-caprolactone and L-lactide P(CL-LLA), epsilon-caprolactone and D,L-lactide P(CL-DLLA) and epsilon-caprolactone and trimethylene carbonate P(CL-TMC) were synthesized. The composition of comonomers and their sequence lengths were determined by means of 1H and 13C NMR measurements. The effect of the comonomer on the thermal properties was investigated by differential scanning calorimetry (DSC) analysis. The in vitro degradation of the rods obtained by melt extrusion of the synthesized copolymers and the commercial homopolymers poly(epsilon-caprolactone) P(CL) and poly(D,L-lactide) P(DLLA) was carried out in phosphate buffer (PB) pH 7.4 at 37 degrees C. The rate of degradation depends on comonomers and polymer composition. The in vitro release of the selected drugs, isometamidium chloride (IMM) and ethidium bromide (EtBr), from such devices was carried out under the same conditions as used for the in vitro degradation. The release experiments show that the release of IMM is faster than for EtBr. During the first stage, for IMM the release is governed by osmotic pressure whereas for EtBr the release is mainly diffusion-controlled. The in vitro release of these drugs is governed by polymer matrix degradation at the later stage of the release process. Comparative in vitro release study from the different polymers showed that the release depends mainly on the physical properties of the polymer. The in vivo experiments carried out in the field on cattle and in the laboratory on rabbits using the classical treatment (intramuscular injection) and the sustained release devices (SRD) subcutaneously implanted, showed that the prophylactic period is significantly enhanced in the case of SRD as compared to intramuscular injection. The comparative efficacy of SRD containing IMM and EtBr evaluated in the case of rabbits showed that, the SRD (IMM) prophylactic period is much longer than for SRD (EtBr).

[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.

Field evaluation of the prophylactic effect of an isometamidium sustained-release device against trypanosomiasis in cattle.

In order to compare the prophylactic effect provided by a poly(D,L-lactide) sustained-release device (SRD) containing isometamidium (ISMM) with that provided by the classical intramuscular injection of the drug, a field trial was carried out at the Madina Diassa Ranch in Mali. One- to 3-year-old N'Dama cattle were randomly divided into three groups. The first group (n = 42) was treated with ISMM at a dose of 1 mg/kg of body weight, the second group (n = 44) received the same dose of the drug via an SRD, which was subcutaneously implanted in the shoulder region, and the third group (n = 36) was kept as an untreated control group. All animals were treated with diminazene aceturate (7 mg/kg of body weight) 2 weeks before the start of the experiment and were tested monthly by the buffy coat technique for a period of 8 months. Glossina morsitans submorsitans was the most important tsetse species, with apparent densities (number of catches/trap/day) varying between 11.9 and 38.7 over the experimental period. Eight months after treatment the cumulative infection rates were 27.7, 58.5, and 77.4% in the group with the SRD implant, the group receiving the intramuscular injection, and the control group, respectively. Statistical analysis showed that the incidence of trypanosomiasis was significantly lower (P = 0.006) in the group which received ISMM via the SRD than in the one which was treated with ISMM intramuscularly.

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.

Comparative evaluation of the prophylactic effect of slow release devices containing homidium bromide and isometamidium on Trypanosoma congolense in rabbits.

Two consecutive experiments were carried out to evaluate the prophylactic effect of biodegradable slow release devices (SRD), containing either isometamidium or homidium bromide. Rabbits subcutaneously implanted with SRD, were challenged with different Trypanosoma congolense stocks at regular intervals between 1 and 6.5 months after treatment. In a first experiment the efficacy of two types of isometamidium-SRD (poly(D,L-lactide) and poly(D,L-lactide-co-glycolide)) was compared with the classical intramuscular (i.m.) injection of the drug. Since the former polymer gave an average protection period, which was much longer than the other isometamidium formulation, a second experiment was carried out to evaluate the prophylactic effect of poly(D,L-lactide) SRD, containing either isometamidium or homidium bromide, with that of the i.m. injections of the same drugs at a dose of 1 mg kg-1. The average protection period of the homidium bromide SRD was significantly longer than that of the i.m. injected drug (112 vs. 49 days). No significant difference was obtained, however, when isometamidium was administered either as a SRD or as an i.m. injection. The average protection periods were, respectively, 106 +/- 37 days and 84 +/- 18 days. When breakthrough isolates derived from SRD-treated animals were compared with the original stocks of T. congolense, the former showed some loss of sensitivity to homidium bromide. No difference in sensitivity was observed, however, for isometamidium.

[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.

Evaluation of the efficacy of a slow release device containing homidium bromide in rabbits infected with Trypanosoma congolense.

The subcutaneous implantation of a slow release device (SRD) containing 1 mg kg-1 homidium bromide (Ethidium) protected 95% of the rabbits for at least 3 months against reinfection with different stocks of Trypanosoma congolense. Only 30.8% of the animals, which received the classical intramuscular injection of 1 mg kg-1 homidium bromide, were protected for more than 1 month. The advantages of an SRD against injection of homidium bromide are a longer protection period, less variation in the percentage of protected animals and the possibility to recover the implants at slaughter. The possible effects on the development of resistance have to be examined further.

Infectivity of Trypanosoma (Trypanozoon) brucei gambiense for baboons (Papio hamadryas, Papio papio).

In order to study sensitivity or resistance of T.b. gambiense to baboon serum, two species of baboons, P. hamadryas and P. papio were inoculated with T.b. gambiense clone LiTat 1.1. Both species were receptive to infection but, parasitological and immunological parameters showed that P. papio was more trypanotolerant than P. hamadryas. The VAT-specific trypanolysis test and the ELISA, using MoAb for circulating antigen detection may be appropriate for the diagnosis of human trypanosomiasis due to T.b. gambiense.

[Epidemiology of bovine babesiosis in south-western Angola]. / Epidémiologie de la babésiose bovine dans le sud-ouest de l'Angola.

An epidemiological survey on bovine babesiosis was carried out in South-Western Angola. Both parasitological and serological methods were used. Use of the packed cell volume (PCV) technique increased up to five times the detection of infected cattle as compared with the thin blood smear method. Although the PCV method provided better information on the parasitological diagnosis, the indirect fluorescent antibody test represents a better approach for the evaluation of endemic situations. Results obtained by this method proved that in most herds and farms investigated there was an endemic stability. The disease did not present any problem in the traditional sector. Cases of babesiosis were only reported in some commercial farms where the control of ticks was inadequate and responsible for endemic instability.

[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.

Chemoprophylaxis of trypanosomiasis, due to Trypanosoma (Nannomonas) congolense, in rabbits using a slow release device containing homidium bromide.

The prophylactic activity of a subcutaneously implanted slow release device, containing homidium bromide, was assessed in rabbits, challenged with different stocks of T. congolense, and compared with the classical treatment of 1 mg homidium bromide/kg b.w. intramuscularly. The prophylactic activity of the intramuscular injection was less than a month, while the slow release device protected the rabbits against seven challenges with T. congolense during a period of more than 300 days.

[Animal reservoir hosts of Trypanosoma brucei gambiense in Zaire: trypanosome infections in two foci in Bas-Zaire]. / Le réservoir animal de Trypanosoma brucei gambiense au Zaire: infections trypanosomiennes dans deux foyers du Bas-Zaire.

The prevalence of Trypanosoma spp. infections in domestic animals was estimated in a forest (Boma) and a savanna (Kimpese) sleeping focus in Bas-Zaire. The miniature anion-exchange centrifugation technique was used to determine the infection rates with T. congolense, T. vivax and T. brucei spp. in 505 animals. T. congolense predominated in both foci with the highest prevalence in pigs (76.2%), followed by sheep (31.3%), dogs (30.6%) and goats (7.4%). T. vivax was seen only on two occasions. In the forest zone, T. brucei spp. infections were frequent (pigs 16.5%, sheep 6.2%, dogs 3.4%, goats 1.1%) in contrast to the savanna area where only one T. brucei spp. infection was diagnosed. Twenty five primary isolations of T. brucei were done using different isolation and stabilization approaches. Isolates and stocks await behavioural, biochemical and molecular biological identification to discriminate T. b. brucei and T. b. gambiense of domestic animal origin.

[Animal reservoir of Trypanosoma (Trypanozoon) brucei gambiense in Central africa]. / Réservoir animal de Trypanosoma (Trypanozoon) brucei gambiense en Afrique Centrale.

The actual available data, from Central as well as from Western Africa, allow us to assert that animals are naturally carriers of T.b. gambiense. Strains from pigs, sheeps and goats have been isolated. However, the importance of animals in the central-west african sleeping sickness epidemiology is still to be specified.