Philippe Brémond

Bio: Philippe Brémond is an academic researcher. The author has contributed to research in topics: Schistosoma haematobium & Schistosoma mansoni. The author has an hindex of 4, co-authored 9 publications receiving 57 citations.

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

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.

Arguments en faveur d'une modification du génome (introgression) du parasite humain Schistosoma haematobium par des gènes de S. bovis , au Niger

Abstract: La caracterisation de schistosomes par la morphologie des oeufs intra-uterins des vers femelles et l'analyse des phenotypes des parasites observes pour la phosphatase acide apres separation electrophoretique suggere la presence de genes de S. bovis, parasite du betail domestique, chez des schistosomes issus de l'homme dans la region est du Niger et presumes appartenir a l'espece S. haematobium

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

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

Urinary schistosomiasis in the Saharan mountain plateau of Air (Republic of Niger)

Abstract: In two villages of the Air (Republic of Niger) the authors have found a Schistosoma haematobium overall prevalence of 24.1% at Timia and 43.5% at El Meki. At El Meki, the distribution of prevalences by age group accords to that which is usually found. The maximum is found in the 5-14 years age group and highest in men than in women. At Timia, the prevalence among young pupils is low, this seems to be due to the application of sanitary education measures. At El Meki, Bulinus truncatus rohlfsi, present in a permanent pool ("guelta") is the intermediate host of schistosomes. The role of this snail in the transmission of urinary schistosomiasis at Timia has not been demonstrated. The role of Bulinus senegalensis, found in both villages has yet to be proved.

Behaviours in trematode cercariae that enhance parasite transmission: patterns and processes.

Abstract: Cercariae, like miracidia, are non-parasitic larval stages implicated in the life cycle of all trematodes for the host-to-host parasite transmission. Almost all cercariae are free-living in the external environment. With a few exceptions (cercariae of Halipegus occidualis (Halipegidae) can live several months, Shostak & Esch, 1990a), cercariae have a short active life during which they do not feed, living on accumulated reserves. Most cercariae encyst as metacercariae in second intermediate hosts which are prey of the definitive host; in certain species, the interruption of the active life is achieved by an encystment in the external environment (or a simple immobile waiting strategy in a few species). In some two-host life cycles, the cercariae develop into adults after penetration (this is the case for various species causing human schistosomiasis). Some cercariae do not leave the mollusc which must then be ingested by the definitive host.

Hybridizations within the Genus Schistosoma: implications for evolution, epidemiology and control.

Abstract: Hybridization of parasites is an emerging public health concern in our changing world. Hybridization and introgression in parasites and pathogens can have major impacts on the host and the epidemiology and evolution of disease. Schistosomiasis is a Neglected Tropical Disease of profound medical and veterinary importance across many parts of the world, with the greatest human burden within sub-Saharan Africa. Here we review how early phenotypic identification and recent confirmation through molecular studies on naturally occurring infections, combined with experimental manipulations, have revealed evidence of viable hybridization and introgressions within and between human and animal schistosome species. Environmental and anthropogenic changes in selective pressures following, for instance, new dam constructions, altered agricultural practices, together with mass drug administration programmes, may all be predicted to further impact the availability of suitable definitive and intermediate hosts for schistosomes. It is therefore imperative to understand the distribution and role of such novel zoonotic hybrid schistosomes on host range, drug efficacy, and hence ultimately transmission potential, if we are to achieve and maintain sustainable control.

Interactions between intermediate snail hosts of the genus Bulinus and schistosomes of the Schistosoma haematobium group.

Abstract: Within each of the four species groups of Bulinus there are species that act as intermediate hosts for one or more of the seven species of schistosomes in the Schistosoma haematobium group, which includes the important human pathogens S. haematobium and S. intercalatum. Bulinus species have an extensive distribution throughout much of Africa and some surrounding islands including Madagascar, parts of the Middle East and the Mediterranean region. Considerable variation in intermediate host specificity can be found and differences in compatibility between snail and parasite can be observed over small geographical areas. Molecular studies for detection of genetic variation and the discrimination of Bulinus species are reviewed and two novel assays, allele-specific amplification (ASA) and SNaPshot™, are introduced and shown to be of value for detecting nucleotide changes in characterized genes such as cytochrome oxidase 1. The value and complexity of compatibility studies is illustrated by case studies of S. haematobium transmission. In Senegal, where B. globosus, B. umbilicatus, B. truncatus and B. senegalensis may act as intermediate hosts, distinct differences have been observed in the infectivity of different isolates of S. haematobium. In Zanzibar, molecular characterization studies to discriminate between B. globosus and B. nasutus have been essential to elucidate the roles of snails in transmission. B. globosus is an intermediate host on Unguja and Pemba. Further studies are required to establish the intermediate hosts in the coastal areas of East Africa. Biological factors central to the transmission of schistosomes, including cercarial emergence rhythms and interactions with other parasites and abiotic factors including temperature, rainfall, water velocity, desiccation and salinity are shown to impact on the intermediate host-parasite relationship.