Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biomphalaria”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,513 records · Page 84Linked to original sources
PubMed1977

Metacercarial cyst formation in vitro of Echinostoma paraensei.

Cercariae of Echinostoma paraensei Lie and Basch 1968 encysted normally in the presence of Biomphalaria glabrata embryo (Bge) cells in culture, partially in culture conditioned medium, and not at all in fresh culture medium alone. At the ultrastructural level the cyst is composed of 2 well defined regions. The outer cyst wall (OCW) is particulate to fibrous in nature, formed from secretory granules released from the cercarial tegument. Membranous scrolls or rodlets secreted from the subtegumental cystogenous gland cells are then added to this layer, forming the inner cyst wall (ICW). After 24 hr the cultured cyst is enclosed by a thin cellular capsule similar to that found around cysts in the snail host. The capsule also contains collagen fibers, not found elsewhere in Bge cell cultures.

Animals↗
PubMed1977

The predatory activity of Lebistes reticulatus (Peters, 1859) on Schistosoma mansoni miracidia in laboratory experiments.

Laboratory experiments were conducted to evaluate the role of the guppy, Lebistes reticulatus (Peters, 1859), as an active predator on Schistosoma mansoni miracidia. When five guppies were introduced into 3.5 liters of water containing 500 and 1200 miracidia on two corresponding tests, a dramatic reduction in number of miracidia was observed. In one experiment, no miracidia could be found after 60 minutes of exposure. The infection rates of vector snails, Biomphalaria glabrata, exposed to approximately 3000 miracidia in the presence of guppies were also greatly reduced. The results obtained suggest that L. reticulatus is a probable predator of S. mansoni miracidia and may, under field conditions, play an important role as a limiting or interfering factor in the transmission of S. mansoni.

Animals↗
PubMed1980

Preliminary epidemiological survey of schistosomiasis in central and southern Liberia.

Some basic epidemiological data on schistosomiasis in central and southern Liberia were collected. A study of snail density fluctuations was carried out in waterbodies bordering the road between Harbel and Gbarnga. Samples from schoolchildren living in ten selected villages were examined for Schistosoma spp. and other helminths. In the coastal region no snail hosts were found, the prevalence rates in schoolchildren were low and the infections were apparently imported. Inland, the intermediate host of Schistosoma haematobium Bulinus globosus was common and the prevalence of urinary schistosomiasis was high. Further inland, around Gbarnga, both Schistosma mansoni and S. haematobium were endemic. The seasonal patterns of patent cercarial infections in Bulinus globosus and Biomphalaria pfeifferi are described. Both snail densities and cercarial infection rates were markedly reduced by heavy rains. The results of the study may contribute to the planning of future integrated control strategy.

Adolescent↗
PubMed1982

[Study of the mechanisms of rejection in incompatible mollusk-schistosome pairs from infestations by means of a natural route or by microsurgical transplantations of parasitic stages].

The non-compatible host-parasite combination used in these studies is an albino Brazilian strain of Biomphalaria glabrata (BRE) and a Guadeloupean strain of Schistosoma mansoni (GUA). This work allows us to emphasize three main points: --The failure of infestation by miracidia transplantations in the non-compatible combination indicates that the origin of resistance does not lie at the level of the tegument, but further away, in the hemolymph of the host. --The results of the histological studies show that the GUA miracidia are completely destroyed 48 h after a natural infection. In addition to the normal reactions of miracidia encapsulation, a degeneration of miracidia without haemocyte participation has also been demonstrated. This degeneration has been interpreted as an indirect proof of the presence of cytophylic factors against the parasite in the plasma of resistant snails. --The results obtained by means of sporocyst transplantations reveal for the first time in vivo the cytotoxic function of haemocytes from resistant B. glabrata. In addition, in vivo studies have demonstrated that the capacity of granulocytes to lyse cells may be much greater than previously suspected. The marked immune response after non-compatible sporocyst transplantation could allow the use of this infection technique as a test of snail-digenea compatibility.

Animals↗
PubMed1983

Studies on the epidemiology of schistosomiasis in Liberia: the prevalence and intensity of schistosomal infections in Bong County and the bionomics of the snail intermediate hosts.

Urine samples from 3548 individuals residing in six of the eight districts which comprise Bong County, Liberia, the project area of the Bong County Agricultural Development Project (BCADP), and fecal specimens from 3408 of these individuals were examined for schistosome ova. A total of 164 water sites, including rice paddies, were surveyed for schistosome vector snails and monthly changes in snail population density and infection rate were determined in selected water sites. Bulinus globosus was more widely distributed than Biomphalaria pfeifferi but the latter species showed a higher infection prevalence (12.3%) than the former one (10.3%). Snail population density and infection rate fluctuated with season, being higher in the dry season and lower during periods of heavy rainfall. Dessication and/or heat stress may have contributed to the contraction of snail population size at the end of the dry season. More water sites contained infected snails during December through February than at any other time of the year. In selected water sites examined at monthly intervals, mean snail density was higher in rice paddies than in other water contact sites but the latter showed a higher prevalence of infected snails than the former. The overall prevalence of Schistosoma mansoni (24.8%) was significantly higher than that of S. haematobium (22.7%) but the difference in prevalence rates of two species in school children was not statistically significant. The intensity of S. haematobium infection (13.2 means G) was significantly higher than that of S. mansoni (6.3 means G). Mixed infections in school children did not have a significant effect on egg output. The prevalence and intensity of S. haematobium showed a dramatic decline between the age groups 0-15 and 20-50 + years old; the differences between these age groups in S. mansoni infection were unremarkable. In Zota, Jorquelle and Kokoya Districts, prevalence rates of S. haematobium were higher than those of S. mansoni; the reverse was observed in Suakoko and Panta-Kpai Districts but relative prevalence rates varied according to specific locality in each district. A south to north stratification of schistosomal infection prevalence was observed similar to the west to east gradient reported by Saladin et al. (1980). New rice paddies developed during the three year operational period of the BCADP contained little or no vector snails and schistosomal infections in farm families of these paddies reflected the characteristic of the disease in corresponding localities.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1983

A pilot control trial of schistosomiasis in central Liberia by mass chemotherapy of target populations, combined with focal application of molluscicide.

In an area of high transmission of Schistosoma haematobium and S. mansoni in Central Liberia, populations of five villages and intermediate host snails were surveyed for two years. In three of these villages focal application of molluscicide (niclosamide) in the main transmission sites was combined with mass chemotherapy of a target population representing 76 to 90% of the contamination index. In the two other villages, which served as control, the prevalence indexes remained stable or increased a little during the period of this study. A three dose metrifonate mass treatment was applied in one village with only S. haematobium infections. The compliance was very poor for the second and third dose but the quantity of eggs eliminated by the whole population present before and after mass treatment was reduced by 50%. No snails were found after molluscicide applications but as the incidence remained unchanged it is suspected that inhabitants have been reinfected by going to their fields. Concurrent metrifonate and niridazole mass treatment in one dose was applied in another village with only S. haematobium infections. Molluscicide applications reduced the snail population by 80% but did not affect the transmission. Prevalence indexes were almost the same before and after this intervention. In the last village, praziquantel (40 mg/kg in 1 dose) was used because both S. haematobium and S. mansoni infections were present. Molluscicide applications reduced the snail population by 99% and 87% for Bulinus globosus and Biomphalaria pfeifferi, respectively. This intervention stopped the transmission of S. haematobium for at least one year and reduced the prevalence from 21% to 4.6%. On the contrary for S. mansoni infections, the incidence remained very high (50%) and the prevalence was unchanged after one year follow-up. This could be explained by lower efficacy of praziquantel against S. mansoni (cure rate: 53%) and of molluscicide application against B. pfeifferi, which are highly susceptible to S. mansoni (infection rate 44%). The importance of migration in these villages is emphasized. Prevalence indexes were largely influenced by the arrival of newcomers who played a more important role in the maintenance of transmission after target mass chemotherapy than the infected persons excluded from this treatment. The costs per capita protected were 3.33 US $ for metrifonate, 1.53 for metrifonate and niridazole combined and 1.67 US$ for praziquantel. These figures do not include costs for parasitological examinations.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1983

Distribution of Helisoma duryi, an introduced competitor of intermediate hosts of schistosomiasis, in an irrigation scheme in northern Tanzania.

Helisoma duryi is a planorbid snail, which has been suggested as biological control agent against the intermediate hosts of schistosomiasis. This snail species has been present in a sugar estate in northern Tanzania since 1972. In January 1981 a snail survey was done in this area in order to determine the distribution and abundance of H. duryi relative to other freshwater snail species. The distribution of H. duryi was found to be restricted to a few drains, while Biomphalaria pfeifferi, Bulinus natalensis, and Lymnaea natalensis were widespread. However, where H. duryi was found, no or very few B. pfeifferi were recorded indicating either competitive interactions between the two species or perhaps differences in the ecological preferences of the two species. No competitive interactions were indicated between H. duryi and B. natalensis. The apparent failure of H. duryi to spread in the area might be due to regular molluscicide application to the canal system and drainage canals, where H. duryi did not occur.

Agriculture↗
PubMed1984

[Selection of genotypes of Schistosoma mansoni and their maintenance by sporocyst transplantation].

Schistosoma mansoni was isolated by hatching eggs obtained from a naturally infected Rat in Grand Etang, Guadeloupe; fifty Biomphalaria glabrata were exposed to five miracidia each. The resulting cercariae were used to infect laboratory mice which were later sacrificed to provide worms for enzyme analyses and eggs for further infections. Seven enzymes in extracts of individual worms were examined by isoelectric focusing in polyacrylamide gels: AcP, G6PDH, PGM, GPI and HK showed no variation, whereas MDH and LDH proved to be polymorphic. Two MDH loci were recognised, MDH-2 was invariant whereas two alleles were assumed at the MDH-1 locus. It was not possible to make a genetic interpretation of the complex banding pattern of LDH, although 4 types (LDH-A, -B, -C, -D) were observed. Of the snail infections, one batch of snails was exposed to 5 miracidia per snail in the normal way whereas other snails were each exposed to a single miracidium. The latter were sacrificed to provide sporocysts to transplant into further groups of recipient snails. Cercariae from the recipient snails were used to infect mice and the adult worms were analysed and compared with the normally passaged material. In this way, three lines, defined by the possession of particular MDH and LDH types, were selected from the originally polymorphic population; two were identical. The combination of single miracidium infections and enzyme typing has illustrated the possibility of selecting parasite lines of known genotype; transplantation of sporocysts from snail to snail has demonstrated that such lines can be maintained exclusively in the intermediate host.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The molluscicidal properties of Ambrosia maritima L. (Compositae). 2. Results from a field trial using dry plant material.

A field trial in Egypt of the plant molluscicide, Ambrosia maritima is described. Applications of 140, 70 and 35 mg/l-1 dry, whole plant were made to irrigation canals and drains in June. The treatment effect took between 1 and 5 weeks to become fully established. The reduction in the numbers of alive Biomphalaria alexandrina snails was generally more than 90% and was virtually the same at all treatment levels and in both types of watercourse. The snail population remained at a low level for at least 3 months until September-October. The possible use of a single, annual application in April or May in controlling snails throughout the main schistosomiasis transmission season in Lower Egypt is suggested.

Animals↗
PubMed1984

Genetic selection for tolerance to niclosamide and copper in Biomphalara glabrata (Mollusca: Pulmonata).

Successive generations of the PR-79 and M-line laboratory stocks of Biomphalaria glabrata were exposed in the LC90 of niclosamide or copper sulfate. Survivors from each generation produced the succeeding generation by self fertilization. The PR-79 stock showed no evidence of tolerance to either molluscicide following five generations of selection. On the other hand, M-line F5 snails demonstrated approximately two-fold higher tolerance to both molluscicides than did non-selected M-line snails.

Animals↗
PubMed1984

[Chemoprophylaxis of schistosomiasis: molluscacidal activity of natural products--assays with adult snails and oviposition].

Data concerning the molluscicidal activity of 159 extracts from 84 Brazilian plants on Biomphalaria glabrata, the most important intermediate host of Schistosoma mansoni in Brazil, are presented. Seventy eight extracts (49,0%) showed activity against snails or eggs, but only twenty nine (18.2%) were active on both, snails and eggs. Extracts of two species (Mikania hirsutissima and Qualea multiflora) have shown to be lethals to adult snails at 10 ppm concentration.

Animals↗
PubMed1975

[Rats and bilharziasis in Guadeloupe].

The rats in Guadeloupe (Rattus rattus and Rattus norvegicus) may play a part in schistosomiasis in three ways: - by harbouring fertile S. mansoni, a fact which serves to increase the total population of the parasite and may eventually take part in the infestation of man; - by harbouring a great number of Ribeiroia marini, a trematode whose larval stages sterilize Biomphalaria glabrata, the vector of schistosomiasis; - simply by eating B. glabrata. The quantitative influence of these contradictory roles played by the rats upon schistosomiasis in Guadeloupe has yet to be studied.

Animals↗
PubMed1982

[Perspectives of the use of Echinostoma togoensis Jourdane et Kulo, 1981 for biological control of intestinal schistosomiasis in Africa].

A study of the experimental development of E. togoensis Jourdane et Kulo, 1981 in its successive hosts has allowed us to show that this species combines several characteristics considered to be essential with a view to biological control of intestinal schistosomiasis: --a complete and permanent sterilizing effect of Biomphalaria pfeifferi; --a pathogenicity with respect to the mollusc in infestations with more than 5 miracidia; --a very clear dominance of intramolluscal stages of Schistosoma mansoni; --ease and low cost of cycle maintenance (the parasite develops in two common hosts: the planorb and the mouse; --a high egg productivity in the mouse (10 mice infected with 75 metacercariea produce on average 620.000 eggs per day.

Africa↗
PubMedDate not supplied

[Epidemiologic study of S. haematobium bilharziasis in the rice fields of Yagoua (North Cameroon) II. Distribution and ecology of intermediate hosts].

While inventoring the local malacological fauna and evaluating the density of species acting as intermediate hosts of human schistosomes it has been shown that Bulinus truncatus is predominant in the study area. Bulinus globosus is scarcely encountered. Biomphalaria pfeifferi is only found in the Mayo Guerleo, in irrigation canals and draining ditches. But B. globosus and B. pfeifferi have not yet invaded the recent aquatic network and are not found in the lake nor in the newly created irrigation systems. Snails shedding cercariae of S. haematobium and S. mansoni have been collected in the area. Bulinus forskalii is found in all types of permanent of temporary waterbodies but S. intercalatum has not yet been reported from North-Cameroon. Lymnaea natalensis, the intermediate host of Fasciola gigantica, is found in the lake and in the canals, in the Mayo Guerleo and in the Toupasko pool. The rice field does not form by itself a favorable environment for snails to develop in it. Spots where transmission occurare more often in the area the secondary of tertiary irrigation canals and the brains. The ditches obstructed by plants are the places where the snails are developing best. Bulinus spp. are found in large numbers in the lowest parts of the aquatic network and they accumulate there to survive drought conditions in the mud. The recently built irrigation systems are not massively invaded by the snails yet and the prevalence of bilharziasis in the area correspond to the distribution of the intermediate hosts of schistosomes and to the density of the snails populations.

Agriculture↗
PubMed1981

Distribution in Kenya of intermediate hosts of Schistosoma.

A major factor in the geographical distribution of endemic schistosomiasis in Kenya is the discontinuous distribution of intermediate hosts. Biomphalaria pfeifferi is the main transmitter of S. mansoni and is found in the altitude zone 300-2,300 m; its absence from the costal region results in the absence of endemic schistosomiasis mansoni amongst the large human population in the coastal region. Snails belonging to the Bulinus africanus group appear to be responsible for all transmission of S. haematobium; they occur from near sea-level to an altitude of about 1,800 but are discontinuously distributed. There appears to be considerable potential for increase in the areas in which each form of schistosomiasis is endemic, taking into account existing patterns of snail distribution and likely developments in irrigation and water conservation. New localities reported here considerably extend the known distribution in western Kenya of B. truncatus, which could serve as an effective intermediate host for S. haematobium if a suitable strain were to become established in Kenya.

Animals↗
PubMed1981

[Contribution to the study of nervous system in larval and adult forms of Schistosoma mansoni Sambon, 1907 (Trematoda Digenea). II. Role of serotonine and dopamine (author's transl)].

This study provides details concerning the localization and role of 5-HT and DA in Schistosoma: 1) 3H-5HT is incorporated selectively by the nerve fibers containing dense granules measuring 820 +/- 20 A (type 2 granules), combined at times with other structures; the presence of "cold" dopamine in the environment does not alter the incorporation; 2) 3H-DA is also incorporated in vitro by the nerve fibers and occasionally by the muscle fibers of the adult Schistosoma; 3) neither the intraovular miracidium, the first and second generation sporocystes, nor the intrasporocystic cercariae appear to incorporate the 3H-5-HT or the 3H-DA, under our working conditions. The two amines are, however, incorporated by the hepatopancreas of Biomphalaria glabrata and the 3H-5-HT produced marking on certain neuromuscular zones of the tentacle.

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↗
PubMed1978

[Molluscicidal properties of the Euphorbia cotinifolia L (author's transl)].

The hexanic extract from the leaves of Euphorbia cotinifolia L. has been experimentally used as molluscicide against Biomphalaria glabrata. The extract was fractionated and the most actives fractions were those of numbers 6 and 7. The lethal concentrations (LC50 and LC90 obtained using fraction 6 against adult snails were 1,2 and 2,4 ppm; for the eggs they were 25,0 and 48,0 ppm. With fraction 7 the lethal concentrations were 1,4 and 3,4 ppm for adult snails; for newly hatched snails they were 4,8 and 8,0 ppm; for the eggs they were 13,0 and 31,0 ppm. In the field the hexanic extract was lethal for the snails in concentrations of 20 ppm in stagnant water. Fractions 6 and 7 were lethal for S. mansoni cercariae and to fish (Lebistes reticulatus) in concentrations below 10 ppm. For mice the extract did not display any toxity in concentrations of 600 mg/kg.

Animals↗