Bulinus species on Madagascar: molecular evolution, genetic markers and compatibility with Schistosoma haematobium.

Of the four species of Bulinus found on Madagascar, three species: B. obtusispira, B. liratus and B. bavayi are endemic while the fourth, B. forskalii, is probably a recent introduction from the African mainland. The evolutionary relationships of these species with Bulinus species from Africa were studied by phylogenetic analysis of DNA sequence variation at two mitochondrial loci: cytochrome oxidase subunit I (COI) and large ribosomal subunit (LSU) or 16S. The observed levels of nucleotide divergence within Bulinus were substantial but may underestimate the true levels as there was evidence of 'saturation' of transitional substitutions at both loci. A putative secondary structure model for the sequenced segment of the 16S was developed. Subsequent phylogenetic analysis using transversional changes only for both loci, showed that there were contrasting levels of divergence within the four species groups. B. obtusispira was consistently placed within the B. africanus group, appearing ancestral to this group and was closest to the basal node within Bulinus. Together with B. bavayi, the two species appear to have been isolated on Madagascar for a long time, contrasting with both B. liratus and B. forskalii that appear more recent colonisers; however, estimate of exact times of divergence is problematic. A PCR-RFLP assay was developed to enable identification and discrimination of B. obtusispira and B. liratus using discriminatory variation within the COI. To enable population genetic analysis within B. obtusispira, microsatellite markers were developed using an enrichment method and 8 primer pairs are reported. Laboratory infection experiments using Madasgacan S. haematobium from the Mahabo area showed that certain populations of B. obtusispira, B. liratus and B. bavayi were compatible.

Intraspecific diversity of Schistosoma haematobium in west Africa: chronobiology of cercarial emergence.

Cercarial emergence patterns were used to analyse the intraspecific variability within and between nine populations of Schistosoma haematobium collected along a transect line from the north to the South of the Ivory Coast (Africa) and using Bulinus truncatus or Bulinus globosus as intermediate snail hosts. Statistical comparison demonstrated the existence of a chronobiological polymorphism and the existence of three homogeneous groups of S. haematobium isolates with mean shedding times of the cercariae decreasing from the North to the South. The chronobiological variability observed was not correlated with the species of Bulinus (B. truncatus vs. B. globosus) implicated in the parasite transmission but with the climatic and vegetal features of the transmission area. S. haematobium from shaded sites of the forest zone (South) showed cercarial emergence patterns significantly earliest than that of S. haematobium from open sites of the savanna zone (North). Differences in sensitivity to light intensity could characterize the existence of eco-geographical races of S. haematobium one of the forest, the other from the savanna.

Vaccination of patas monkeys experimentally infected with Schistosoma haematobium using a recombinant glutathione S-transferase cloned from S. mansoni.

The capacity of a recombinant glutathione S-transferase from Schistosoma mansoni (rSm28GST) to vaccinate primates (Erythrocebus patas) against a heterologous infection with Schistosoma haematobium has been tested. Two injections of the purified molecule with Muramyl-Di-Peptide (MDP) as adjuvant resulted in a high level antibody response in the five immunized animals and in a significant reduction in worm fecundity compared to the controls which received adjuvant alone. Mean levels of daily egg excretion in urine an faeces were reduced by respectively 55% and 74% although perfusion revealed that worm burdens were similar in both groups. The protective effect was long lasting since it was maintained up to the end of the experiment, 42 weeks after infection. Hatching rates and the numbers of intra-uterine eggs were also significantly affected by the vaccination. Tissue eggs were also drastically diminished in the urogenital system (-80%) but the reduction was not statistically significant. One animal was not protected by the immunization. There was a good correlation between parasitological data and the intensity of bladder lesions assessed by microscopic examination. Polypoid formations together with an intense exudation of the lamina propria were frequently seen in the controls but rarely in the vaccinated group where formation of scar tissue was predominant. These results underline the vaccine potential of the recombinant Sm28GST as a possible valuable prophylactic tool for the control of egg-induced pathology and transmission of African schistosomes.

Vaccination of goats against the trematode Schistosoma bovis with a recombinant homologous schistosome-derived glutathione S-transferase.

We assayed the vaccine potentialities of a recombinant S. bovis-derived glutathione S-transferase (rSb28GST), member of a molecular family already shown to have protective capacities in the S. mansoni and S. japonicum models. Injection of the rSb28GST in Freund's Complete Adjuvant resulted in good specific IgG responses allowing all the animals to display high antibody titres on the day of experimental challenge with S. bovis cercariae. No statistically significant differences were observed in the faecal egg output. Although tissue egg counts in vaccinated animals were lower than in controls, the difference was not statistically significant, apart from the number of eggs trapped in the liver (P < 0.05). Likewise, PCV values remained parallel between the two groups. However, immunized goats gained 1.4 kg of body weight throughout the experiment whereas controls lost 1.2 kg (P < 0.05). In addition, the mean worm burden, assessed by perfusion 20 weeks after infection, was significantly reduced by 48% in the vaccinated group, the sex ratio being unaffected. It appears that a recombinant homologous protein can affect, in a natural host, the course of an experimental infection with a local strain of S. bovis, by affecting worm viability but not fecundity. These results also point to the striking differences in the effect of vaccination according to animal species. Because it has the capacity to prevent growth impairment due to schistosome pathogenicity, the molecule can be proposed as a valuable tool in the development of vaccine-based control programs in endemic areas.

[Arguments for the modification of the genome (introgression) of the human parasite Schistosoma haematobium by genes from S. bovis, in Niger]. / Arguments en faveur d'une modification du génome (introgression) du parasite humain Schistosoma haematobium par des gènes de S. bovis, au Niger.

Characterization of schistosome populations from human in eastern Niger, through intra-uterine egg morphology of female parasites and phenotopic analyses of worms observed for acid phosphatase using electrophoretic separation, renders results that suggest an intogression of S. haematobium from man by genes of S. bovis, a parasite of domestic livestock. The origin of this introgression, that could implicate S. curassoni as well, another livestock parasite that hybridize with S. bovis, is discussed.

Pattern of cercarial emergence of Schistosoma curassoni from Niger and comparison with three sympatric species of schistosomes.

The emergence pattern of Schistosoma curassoni cercariae from Bulinus umbilicatus, whose adult worms parasitize bovine, caprine, and ovine ungulates in Niger, is of a circadian type with a mean emission time at 0855 hr +/- 1 hr 6 min, characteristic of the schistosome species parasitizing domestic or wild cattle. The comparison of this cercarial emergence pattern with those of the other 3 sympatric species of schistosomes (Schistosoma haematobium, Schistosoma bovis, and Schistosoma mansoni) shows a significant difference between the chronobiology of the cercariae infective for human and those infective for bovine hosts. This difference may improve epidemiological surveys based on snail prevalences by allowing the distinction between bulinids infected with human and bovine parasites.

Urinary tract lesions due to Schistosoma haematobium infection assessed by ultrasonography in a community based study in Niger.

The comparative prevalences of urinary tract lesions in 2 villages where urinary schistosomiasis was endemic and in a control village free from infection were assessed by ultrasonography. Of the 822 residents greater than 4 years of age in the first village (Sébéri) where the prevalence of infection was 57%, 279 were examined by ultrasonography. The prevalence of bladder lesions was 71% in those 5-14 years of age, 57% among adult men, and 24% among women in this endemic village, compared to 10%, 16%, and 6%, respectively, in the control village. Renal lesions were infrequent among adults and there was no significant difference in the rates between Sébéri and the control village. Among children, moderate hydronephrosis was absent in the control village, but was observed in 19% of the boys 5-14 years of age and 2% of the girls 5-14 years of age in Sébéri. Sixty schoolchildren of the second endemic village with urinary egg counts greater than or equal to 100 eggs/10 ml of urine were examined by ultrasonography. The overall prevalence and the severity of bladder lesions in the 2 endemic villages were significantly related to the urinary egg count.

[Chemotherapy trial in the battle against Schistosoma haematobium in an irrigated sahelian zone in Niger]. / Essai de lutte par chimiothérapie contre Schistosoma haematobium en zone irriguée Sahélienne au Niger.

This study of S. haematobium infection in communities associated with irrigated schemes shows that prevalence rates are unusually high in adults, especially in men; and distribution disease is probably associated with at least the following three factors: (i) distance of the place of residence from the main transmission sites (ii) the dynamics of transmission in the waterbody and (iii) the human/water contact and contamination patterns. During this chemotherapy trial, at the first survey, only a little more than half (57.47%) of the people recorded in the census was present. Five visits of the survey team were necessary to obtain a compliance rate of 80.51% of the entire population. The indifference of the local people to seek diagnosis and treatment increased with succeeding surveys. It is only, during a subsequent treatment survey, carried out during the season of low agricultural activity and following an official written convocation, that a compliance rate similar to that of the first survey was recorded. If treatment is not given immediately after diagnosis as many as a fifth of positive cases do not appear for treatment. Oltipraz and praziquantel were administered. Their effectiveness could not be truly compared as there was a time lag of six months separating the administration of the treatments. However, based on the results of this trial both drugs gave good results especially in egg output intensity. But, a decrease of this parameter was also observed in non treated people. Seasonal variations of egg output or decrease of transmission could be involved.

[Effectiveness of an amphoteric surface agent against Schistosoma mansoni miracidia in field-like conditions in Niger]. / Efficacité d'un agent de surface amphotère contre les miracidiums de Schistosoma mansoni dans des conditions dé terrain au Niger.

The laurylamidopropylbétaïne, a surface active substance, has been tested in field conditions, in Niger, against Schistosoma mansoni miracidia. Experiments were carried out in artificial ponds of 20 m3, in which conditions were similar, as far as possible, to conditions found in transmission sites. The product showed a satisfactory remanence and the percentage of infected molluscs dropped down to zero with a low (2 ppm) concentration. It is suggested that laurylamidopropylbetaïne could be used into soaps in order to renew constantly the product in washing and bathing places and reduce schistosome transmission.

[Urinary bilharziasis and sideropenic anemia. Study of their relation in 2 villages in Niger]. / Bilharziose urinaire et anémie sidéropénique. Etude de leurs rapports dans deux villages du Niger.

In order to assess Schistosoma haematobium as an aetiologic factor in sideropenic anaemias, we compared a village with high prevalence of urinary schistosomiasis and a village without urinary schistosomiasis as a control. In the infested village, anaemias (haemoglobin value lower than 12 g/dl) especially affects children between 5 to 14 years old (71%:45/68). Boys being the most infestated group with S. haematobium (prevalence:100%; mean egg output: 496 eggs/10 ml of urine) are also the most anaemic group (82%:23/28). Comparing the two villages shows that urinary schistosomiasis increases the risk of acquiring anaemia by 30% among children aged 5 to 14. Furthermore, the parasitic disease reduces of 1 g/dl the mean haemoglobin level of adult males. On the other hand, S. haematobium is of minor importance as a cause of anaemia among women. The others aetiologies remain preponderant.

[Course of urinary schistosomiasis over 3 consecutive years after treatment with metrifonate in a dry savanna village in Upper Volta]. / Evolution sur trois années consécutives de la schistosomose urinaire après traitement au metrifonate dans un village de savane seche de Haute-Volta.

In a dry savanna village in Upper-Volta, after mass treatment with metrifonate (four doses of 7,5 mg/kg at three weeks intervals) checking of the population was carried out for the three following years. In children and adolescents, results show a progressive decline in the cure rate (69.0% one year after treatment, 38.1% three years after treatment) and in egg-output reduction (69.9% one year after treatment, 75.4% three years after treatment). In adults, these two parameters still remain high three years after treatment (90.0% for cure rate and 87.3% for egg-output reduction). The authors point out that in a dry savanna village with a sedentary population and a transmission limited to a small collection of water, chemotherapy even employed alone is an appreciable control method to relieve populations.

[Comparative efficacy of oltipraz (1 dose, 30 mg/kg) and the combination of niridazole (25 mg/kg) and metrifonate (10 mg/kg) against S. haematobium]. / Efficacité comparée de l'oltipraz (1 dose, 30 mg/kg) et de l'association niridazole (25 mg/kg) - métrifonate (10 mg/kg) contre S. haematobium.

PUGH (1978) and TEEDSALE et al. (1980) showed that an associated single dose of metrifonate (12.5 mg/kg) plus niridazole (25 mg/kg) gave good results on Schistosoma haematobium: the egg-reduction percentage ranged between 84.7 and 91.2. In Niger, we compared the effects of this medication to oltipraz in a single dose (30 mg/kg). We selected a dosage of 10 mg/kg of metrifonate and 25 mg/kg of niridazole. This trial was carried out during the minimal transmission period. --109 adults (greater than 15 years) received oltipraz and 159 this combined treatment. They were examined twice: 11/2 month and 6 months after treatment. At the first control, the cure rate was 26.7% for oltipraz and 23.3% for the combined treatment, the egg-reduction was respectively 77.1% and 41.3%. Six months after treatment, the cure rate was 43.5% for oltipraz and 27.7% for the combined treatment and the egg-reduction was 66.5% and 2.0% respectively. Following these results, the authors recommend against the combined treatment in Niger. They note that if, in some particular conditions, this medication can give good results (PUGH, 1978, TEESDALE et al., 1980) it is however necessary to include its test in future control projects. Also, they note the weak result obtained with oltipraz; but, in this case, the heavy endemic level and high egg-loads might explain it, as well as the fact that the 30 mg/kg dosage was probably insufficient.

[Trial control by metrifonate chemotherapy of Schistosoma haematobium in a dry savannah zone in Upper Volta]. / Essai de lutte par chimiothérapie au métrifonate contre "Schistosoma haematobium" en zone de savane sèche de Haute-Volta.

Metrifonate (Bilharcil) was administered in a dose of 7,5 mg/kg, four times at 3 weeks interval to all villagers, regardless of the result of parasite examination, in order to test this treatment of urinary schistosomiasis in a hyperendemic village. On the year following the treatment, three parasite surveys were carried out. They showed a decline in the prevalence and a decrease in number of eggs excreted in the urine. The decrease rate was 91% to 94% in the 10-14 years group, the group with the highest infectivity.

[Urinary schistosomiasis. 1st trial of mass treatment in the field (Niger)]. / Schistosomose urinaire. Premier essai de traitement de masse sur le terrain (Niger).

In a village of 841 inhabitants, we were able to examine 553 subjects, 357 of whom had urinary egg excretion. The patients were treated with a single dose of 35 mg/kg oltipraz which was given under surveillance together with either whole milk or herrings in oil. The tolerance of the product was very good as only 3% of the patients reported vomiting and 3% paresthesias of the fingers. 66% of the patients examined on day 30 and/or on day 90 were egg-negative and egg excretion was reduced by at least 90% in 22 other subjects, bringing the percentage of good results to 74%. On day 90, the mean egg excretion was reduced by 82.5% in the overall population and by 80.9% in the 5 to 14 year-olds.

[Value of macroscopic urine examination and reagent strips for the detection of hematuria and proteinuria in the mass diagnosis of urinary schistosomiasis, before and after treatment]. / Valeur de l'examen macroscopique des urines et des bandelettes réactives pour la détection de l'hématurie et de la protéinurie dans le diagnostic de masse de la schistosomiase urinaire, avant et après traitement.

In this study, dip-stick examination for the detection of hematuria and proteinuria, and macroscopic examination of the urine as diagnostic methods for mass screening for urinary schistosomiasis, were compared with the technique of urinary filtration for Schistosoma haematobium eggs. Dip-sticks and macroscopic examination were proved to be simple and rapid. Before treatment, the revealing of hematuria by dip-stick was shown to be a sensitive method by comparison with filtration, but it is not specific. The tests for proteinuria, and macroscopic examination are more specific, but less sensitive. Nevertheless, all these methods give similar prevalences as distributed by age groups. Dip-sticks and macroscopic exams could therefore be duly considered for the detection of new high endemic regions. After treatment, these methods result in less valid prevalences than those obtained by filtration, but their specificity increases; they become good indicators of clinical improvement.