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Journal ArticleDOI

The WHO Collaborating Centre for Research and Control of Schistosomiasis at Niamey, Niger.

01 Sep 1997-Memorias Do Instituto Oswaldo Cruz (Instituto Oswaldo Cruz, Ministério da Saúde)-Vol. 92, Iss: 5, pp 725-728
TL;DR: The CERMES defined the different patterns of schistosomiasis transmission in Niger and shown the existence of important variability in conditions of transmission of S. haematobium.
Abstract: The Centre de Recherche sur les Meningites et les Schistosomoses (CERMES) a research center in Niamey Niger affiliated with a West African public health organization conducts studies in the areas of parasitology epidemiology and immunology Significant variability in factors related to transmission of Schistosoma haematobium have been noted Experimental research on the Schistosoma-bulinid compatibility and field surveys of the geographic distribution and role of snails in transmission have been essential to the design of parasite control interventions in West Africa A CERMES-sponsored project supported by the European Community is examining urinary schistosomiasis control in the Niger river valley and the impact of treatment on ultrasonically visualized urologic lesions The Experimental Vaccine Unit seeks to improve the route of administration and choice of adjuvant and to propose a vaccine protocol for field testing Recombinant proteins have been found to alter the development of the parasite either by inducing a reduction in the parasite burden or an inhibition of the fecundity of the parasite
Citations
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Journal ArticleDOI
TL;DR: To enable differential detection of S. haematobium DNA by simple polymerase chain reaction (PCR), designed and tested primer pairs from numerous newly identified Schistosoma DNA repeat sequences, but all pairs tested were found unsuitable for this purpose.
Abstract: Schistosoma haematobium infects nearly 150 million people, primarily in Africa, and is transmitted by select species of local bulinid snails. These snails can host other related trematode species as well, so that effective detection and monitoring of snails infected with S. haematobium requires a successful differentiation between S. haematobium and any closely related schistosome species. To enable differential detection of S. haematobium DNA by simple polymerase chain reaction (PCR), we designed and tested primer pairs from numerous newly identified Schistosoma DNA repeat sequences. However, all pairs tested were found unsuitable for this purpose. Differentiation of S. haematobium from S. bovis, S. mattheei, S. curassoni, and S. intercalatum (but not from S. margrebowiei) was ultimately accomplished by PCR using one primer from a newly identified repeat, Sh110, and a second primer from a known schistosomal splice-leader sequence. For evaluation of residual S. haematobium transmission after control interventions, this differentiation tool will enable accurate monitoring of infected snails in areas where S. haematobium is sympatric with the most prevalent other schistosome species.

34 citations

Book ChapterDOI
TL;DR: In this paper, the authors report on the epidemiology and control of schistosomiasis in the Economic Community of West African States (ECOWAS), which represents 30% of the total population of the African continent.
Abstract: The present study aims to report on the epidemiology and control of schistosomiasis in the Economic Community of West African States (ECOWAS), which represents 30% of the total population of the African continent. Fifteen states are included in ECOWAS, three of which were elected by the Schistosomiasis Control Initiative: Mali, Niger and Burkina Faso, the other 12 countries being Benin, Cape Verde, Cote d'Ivoire, The Gambia, Ghana, Guinea, Guinea Bissau, Liberia, Nigeria, Senegal, Sierra Leone and Togo. For each country we updated, according to the different administrative regions of the country, the epidemiological data concerning the prevalence of human schistosomiasis and the prevalence of snail schistosomiasis and the control programmes each country is developing. The study highlights the common data in ECOWAS regarding the status of the infected people, the causes of schistosomiasis infection, the epidemiology of Schistosoma haematobium and Schistosoma mansoni in relation to their respective snail intermediate hosts, Bulinus and Biomphalaria. The new epidemiological approaches generating maps of zones of disease risk will provide helpful tools for schistosomiasis control.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the efficiency of the oral, intramuscular and subcutaneous routes are evaluated by comparison with the percutaneous route in experimental infections with S bovis.

8 citations

Journal ArticleDOI
TL;DR: A new PCR assay was sensitive, specific and was able to successfully differentiate S. haematobium from S. magrebowiei, in addition to its other closely related animal infective schistosome species.
Abstract: Introduction: Schistosoma haematobium infection afflicts about 150 million people in 53 countries in Africa and the Middle East. In many endemic areas, S. haematobium is sympatric with Schistosoma bovis, Schistosoma mattheei, Schistosoma curassoni, Schistosoma intercalatum and Schistosoma magrebowiei, its closely related species. In addition, they also develop in the same intermediate snail hosts. Since these schistosome species often infect snails inhabiting the same bodies of water, examining cercariae or infected snails for estimating transmission of S. haematobium is always confounded by the need to differentially identify S. haematobium from these other species. Recently, differentiating S. haematobium by polymerase chain reaction (PCR) from S. bovis, S. mattheei, S. curassoni and S. intercalatum, but not from S. magrebowiei was reported. However, to be able to evaluate residual S. haematobium transmission after control interventions in areas where S. haematobium may be sympatric with S. magrebowiei, a differential tool for accurate monitoring of infected snails is needed. Materials and Methods : Thus in this study, we developed a new PCR assay using a pair of primers, ShND-1/ShND-2, to amplify a target sequence of 1117 bp (GenBank accession number KF834975) from S. haematobium mitochondrion complete genome (GenBank accession number DQ157222). Sensitivity of the assay was determined by PCR amplification of different concentrations of S. haematobium gDNA serially diluted from 10ng to 0.1pg. For assay specificity, different concentrations of gDNA from S. haematobium and the other schistosome species, 20 positive urine samples and five controls as well as 20 infected snails were subjected to PCR amplification, while some of the PCR products were sequenced. Results : The assay detected up to 1pg of S. haematobium gDNA, while a differential identification of S. haematobium DNA content from other closely related species was achieved when applied to urine and naturally infected snails. When a protein-protein blast search was carried out using Blastp, the amplified sequence was found to encode a protein that shows a 100% similarity with S. haematobium nicotinamide adenine dinucleotide dehydrogenase subunit 3 (GenBank accession number YP_626524.1). Conclusion : The PCR assay was sensitive, specific and was able to successfully differentiate S. haematobium from S. magrebowiei, in addition to its other closely related animal infective schistosome species.

8 citations

Journal ArticleDOI
TL;DR: In this article , a cross sectional survey based on a random sample drawn from the population to detect infections with S. haematobium and S. mansoni was conducted in Ounianga in Northern Chad.
Abstract: Researching a water-borne disease in the middle of the Sahara desert might not seem the most relevant concern. However, nomadic Sahelian pastoralists health concerns regarding their livestock and anecdotal reports about trematode infections of Fasciola spp. and Schistosoma spp. in desert-raised animals justified an exploratory study focusing on the lakes of Ounianga in Northern Chad. The aim was to test whether trematode parasites such as Schistosoma spp. occur in human populations living around the Sahara desert lakes of Ounianga Kebir and Ounianga Serir in northern Chad.The study was carried out in January 2019 and comprised of three components. First, a cross sectional survey based on a random sample drawn from the population to detect infections with S. haematobium and S. mansoni; second, focus group discussions exploring disease priorities, access to health and health seeking behaviour; and third, surveying water contact sites for intermediate host snails. Samples of trematode parasites and snails were confirmed on species level by molecular genetic methods. For parasitological and malacological surveys descriptive statistics were performed. Qualitative data analysis included the full review of all transcripts, followed by a descriptive and explorative thematic analysis.Among 258 participants, the overall S. haematobium prevalence using urine filtration was 39.2% [95% confidence interval (CI): 33.5-45.1%], with 51.5% of the infected suffering from heavy infection. The intermediate host snail of S. haematobium (Bulinus truncatus) occurred at water contact sites near both study villages, revealing the potential for local transmission. Although a positive S. mansoni point-of-care circulating cathodic antigen (POC-CCA) test result was obtained from 8.6% (95% CI 5.7-12.8%) of the samples, no intermediate host snails of S. mansoni were found, and the relevance of S. mansoni remains uncertain. Qualitative findings underline the importance of morbidity caused by urinary schistosomiasis, and the lack of access to diagnostics and treatment as a major health concern.This research revealed a high prevalence of urinary schistosomiasis in the population living around the lakes of Ounianga in the Sahara, a United Nations Educational, Scientific and Cultural Organization (UNESCO) world heritage site in Chad. Despite the high public health importance of the associated morbidity expressed by the population, there is no access to diagnostics and treatment. Further work is needed to develop and test a context-adapted intervention.

3 citations

References
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Journal Article
TL;DR: In this article, it was shown that immunization with Sm28 GST was shown to reduce significantly parasite fecundity and egg viability leading to a decrease in liver pathology in human populations.
Abstract: Two specific characteristics of schistosome infection are of primordial importance to the development of a vaccine: schistosomes do not multiply within the tissues of their definitive hosts (unlike protozoan parasites) and a partial non-sterilizing immunity can have a marked effect on the incidence of pathology and on disease transmission. Since viable eggs are the cause of disease pathology, a reduction in worm fecundity whether or not accompanied by a reduction in parasite burden is a sufficient goal for vaccine induced immunity. We originally showed that IgE antibodies played in experimental models a pivotal role for the development of protective immunity. These laboratory findings have now been confirmed in human populations. Following the molecular cloning and expression of a 28 kDa protein of Schistosoma mansoni and its identification as a glutathione-S-transferase, immunization experiments have been undertaken in several animal species (rats, mice, baboons). Together with a significant reduction in parasite burden, vaccination with Sm28 GST was recently shown to reduce significantly parasite fecundity and egg viability leading to a decrease in liver pathology. Whereas IgE antibodies were shown to be correlated with protection against infection, IgA antibodies have been identified as one of the factors affecting egg laying and viability. In human populations, a close association was found between IgA antibody production to Sm28 GST and the decrease of egg output. The use of appropriate monoclonal antibody probes made it possible to demonstrate that the inhibition of parasite fecundity following immunization was related to the inhibition of enzymatic activity of the molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

56 citations

Journal ArticleDOI
TL;DR: The 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.
Abstract: 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.

45 citations

Journal ArticleDOI
TL;DR: It appears that a recombinat homologous protein can affect the course of an experimental infection with a local strain of S. bovis, by affecting worm viability but not fecundity, and can be proposed as a valuable tool in the development of vaccine‐based control programs in endemic areas.
Abstract: SUMMARY 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 1·2kg (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 recombinat 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.

41 citations

Journal Article
TL;DR: This study shows that the main types of aquatic environments on the Niger act as high risk areas for schistosome transmission, which strongly suggests a lack of isolation in schistoome populations and a circulation of the parasite genome through the mobility of infected human populations in Sahel zone.
Abstract: A populational study of the compatibility be- tween Scliistosoma lzaematobiurn and its potential vectors has been carried out in the Niger, confronting samples of S. haeinatohiunz populations from three epidemiologic foci with Bulinus populations originating from the same focus (sympatric infection) and with Bulinus populations from other foci (allopatric infections). The three transmis- sion foci selected were irrigation canals in ricefields along the Niger river where one finds: Bulinus truncatus rohlfsi, Bidinus globosus, Bulinus forskalii and Bulinus senegalensis; temporary pools in the Sahel area where one finds B. trzmca- tus and B. senegalensis; permanent pools of the "guelta" type in Sahara area where only B. truncatus occurs. As a compatibility test, the snail infection test was selected, with particular emphasis on optimising its reliability. Snail-in- fection experiments showed that B. trzmcatus.and B. sene- galensis are very good potential vectors, with infection rates ranging between 71.5 and 85.9%. B. globosus and B. forska- Zii, on the other hand, are totally incompatible. The mean in- fection percentages in the sympatric and allopatric combi- nations carried out with the S. haenzatobiuin-B. truncatus couple were very similar. This character strongly suggests a lack of isolation in schistosome populations and a circula- tion of the parasite genome through the mobility of infected human populations (Peuls and Touaregs) in Sahel zone. This study, in relation with snail surveys carried out in par- allel, shows that the main types of aquatic environments on the Niger act as high risk areas for schistosome transmis- sion.

37 citations

Journal ArticleDOI
TL;DR: 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 as mentioned in this paper.
Abstract: 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.

29 citations

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