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Biomedical subjects

C Combes

Publications and source records attributed to C Combes.

At least 73 records · Page 4Linked to original sources
PubMed1986

[Effectiveness of an amphoteric surface agent against Schistosoma mansoni miracidia in field-like conditions in 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.

Animals↗
PubMed1986

Interaction between the Biomphalaria glabrata-Schistosoma mansoni host-parasite system and the non-target molluscs: influence on cercarial production.

The cercarial production of Schistosoma mansoni by Biomphalaria glabrata (target mollusc: TM) was studied in relation to the presence of non-target molluscs (NTM). Nine species of NTM were tested. Whatever the type of TM-NTM association (lasting association, during prepatent period and production period, association only during the exposure of the molluscs to the miracidia), the presence of NTM involved a significant increase of S. mansoni cercarial production. This increased cercarial production was more or less pronounced according to the NTM species present.

Animals↗
PubMed1985

[Analysis of schistosome/molluscan vector compatibility].

The compatibility between Schistosomes and Molluscs cannot be accurately analysed by a single method. When a given host-parasite pairing is studied, it is necessary to test separately the performance of the parasite against the Mollusc, the performance of the defense mechanisms of the host and the performance of the host-parasite system when producing cercariae. In addition, the usual laboratory "strains" are not suitable for population genetics studies because of the impoverishment of the gene-pool.

Animals↗
PubMed1985

[The choice of intermediate molluscan host by the miracidium of Schistosoma bovis].

When the usual intermediate hosts (B. truncatus and P. metidjensis) and several other species of Molluscs are together exposed to the miracidia of S. bovis, we demonstrate that about 75% of the miracidia penetrate B. truncatus and P. metidjensis, while 25% penetrate the Pulmonates (B. glabrata, B. straminea and H. duryi) and no miracidium penetrates the Prosobranches (M. tuberculata, M. cornuarietis). When the miracidia penetrate the non-vector Molluscs, it takes less than 24 hours for them to get encapsulated, except for B. straminea, in which the reaction takes 24 to 48 hours.

Animals↗
PubMed1983

[Genetic analysis of the shedding pattern of Schistosoma mansoni cercariae by hybridization of species with early and late emission peaks].

The hybridization between Schistosomes (S. mansoni) with an early and a late shedding pattern of cercariae lead to heterozygotous cercariae whose shedding pattern is characterized by two peaks (early and late). These results demonstrate the genetic support of the shedding rhythm of cercariae and suggest the participation of the daughter sporocyst in the chronobiological phenomenon of cercarial shedding.

Animals↗
PubMed1983

[Possibilities of using amphoteric surface agents in the campaign against the agents of schistosomiasis transmission].

Among the chemicals which might be used against the larvas of Schistosoma, some surface active substances show some high activity at very low concentrations (0,1-5 ppm) against the miracidiums and the cercariae. The laurylamidopropylbetain has shown out of a group of products which were tested, a very high activity by lowering considerably the infection by the larvas of the hosts, like molluscs and mice, which were in contact with them. After a serie of tests made in Nigeria, these products showed a satisfactory remanence in tropical waters, in spite of the biodegradation and the adsorption on the suspended particles. It was faced to put that betain into soaps at a concentration of 5% which will permit to renew constantly the active product and which will reduce heavily any infection.

Animals↗
PubMed1982

[Evaluation of 10 years of research on S. mansoni schistosomiasis A in the French West Indies].

From 1971 until 1982, we studied the ecological factors which stead fast a perennial schistosomiasis in Guadeloupe on an exhaustive mode. More recently, we start a similar investigation in Martinique. In Guadeloupe the single vector of Schistosoma mansoni is the snail Biomphalaria glabrata which is an ubiquist species. But the transmission to man is restricted to the "canal-sewers" where faeces are dropped and not in the rivers of Basse-Terre or the ponds of Grande-Terre. Moreover, the infection is possible only during the hottest hours of the day, when the cercariae get out of the snail. We built a "cercariometer" with which we are able to know the number of cercariae per litre in a given place at every hour of day and night. The black rat (and not the grey rat!) seems, alone, able to maintain the life-cycle of the parasite, at least in the mangrove forests. It is now possible to "clone" S. mansoni by sporocysts transplantation in non-infected snails. The biological control of B. glabrata populations is possible by sterilizating Trematodes such as Ribeiroia guadeloupensis. A new built irrigation reservoir in Grande-Terre give a chance of spread for the endemy in an area which was, till now, unharmed.

Animals↗
PubMed1980

Infectivity in rodents of Schistosoma mansoni cercariae of human and murine origin.

Experimental infections of white laboratory mice and wild rats (Rattus rattus) with cercariae of Schistosoma mansoni of different descent, whether murine or human, demonstrate that there is no significant difference in the probability of maturation of these cercariae into adult schistosomes. These results enable us to hypothesize that the reverse would be true, i.e. that cercariae of murine or human descent would be capable of infecting man with the same success rate. Circulation of the parasite from man to the rat and from the rat to man may therefore occur in natural habitats, which does not mean that rodents can maintain indefinitely and independently Schistosoma mansoni, nor does it mean that murine strains may not evolve locally.

Animals↗
PubMed1980

Demonstration of several sporocysts generations as a normal pattern of reproduction of Schistosoma mansoni.

A thorough study of the development of Schistosoma mansoni demonstrates that asexual reproduction within the vector-mollusc does not proceed according to the usually accepted process. Under natural conditions, daughter sporocysts are capable fo stopping production of cercariae and orienting production towards an additional generation of sporocysts, which themselves will be able to evolve in the same manner. This process intervenes without exception provided that the duration of parasitosis exceeds 40 days (at 26 degrees C). It is observed in three different american strains of S. mansoni. We believe that this is the first demonstration of the existence of several sporocysts generations as an habitual mode of reproduction in the life cycle of Digenea.

Animals↗
PubMed1978

[Ecology of intestinal schistosomiasis in Guadeloupe. Epidemiological analysis and data for a model study (author's transl)].

In Guadeloupe, during a general survey on intestinal schistosomiasis, the authors made a structural analysis of a limited focus of infection. The focus is formed by a river basin on the Carribean coast of Basse-Terre island. Sampling of the various elements of the parasitic cycle was done in spatial units defined by ecological and epidemiological criteria. The study of corresponding populations shows that: -- inside the twelve delimited sectors, only two include both hosts and parasites. They are zones with ditches and small temporary streams; -- the vector (Biomphalaria glabrata) density is always high in inhabited sectors; -- the rat, although present over the whole river basin, is only parasitized near inhabited places; -- fluorescent antibody level is an excellent indicator of the level of infection of human populations. Its variation can be detected in a time interval of less than one year; -- distance from contaminated water is one of the principal risk factors. A mathematical expression for this is given.

Adolescent↗
PubMed1977

[Coexistence of neoteny and an internal cycle a polystomatid (Monogenea)].

Metapolystoma cachani a parasite of Ptychadena longirostris (Peters) has been discovered in the Ivory coast. Its life cycle is the first to involve both the possibility of an internal cycle in the bladder of the adult Amphibian and a neotenical reproduction on the gills of the Tadpole. This double process is the link between the Monogeneans which are only parasites of aquatic hosts and those which are adapted to terrestrial hosts. Its place is therefore essential in the phylogeny of Polystomatidae.

Amphibians↗
PubMed1975

[Endocellular pathogenic bacteria in the monogenean Euzetrema knoepffleri].

Intracellular bacteria (Rickettsia) are found in the Monogenean Euzetrema knoepffleri, vesicular endoparasite of the Amphibian Euproctus montanus (Urodela). In some conditions, they cause cytoplasmic damage in the host tissues, which demonstrates their pathogenicity. These bacteria are present during all the stages of the life-cycle of E. knoepffleri. Their transmission from one generation to the next occurs through the gametes.

Amphibians↗
PubMed1975

[The role of the rat in the dynamics of endemic schistosomias in Guadeloupe].

In Guadeloupe (French Lesser Antilles), because they are simultaneously infested with Schistosoma mansoni, which causes the human intestinal schistosomiasis, and Ribeiroia marini, a Trematode which sterilizes the Mollusk-host of the schistosoma, the rats (Rattus rattus and Rattus norvegicus) seem able to influence, at least locally, the infestation of the human population.

Animals↗