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PubMed2006

Behavior of Angiostrongylus costaricensis in planorbids.

Some terrestrial mollusks are natural hosts of Angiostrongylus costaricensis. In the laboratory, this nematode can be maintained in certain planorbids, which are aquatic mollusks and intermediate hosts of Schistosoma mansoni. Mollusks can be infected with Angiostrongylus costaricensis by ingestion of or active penetration by the first-stage larvae. In this work we assessed the ability of Biomphalaria glabrata to attract first-stage larvae of A. costaricensis. Movement of the nematode larvae towards the mollusks was observed after 15 min, 30 min and 1 h. B. glabrata did not attract the first-stage larvae of A. costaricensis in any of the three intervals. The susceptibility of two populations of Biomphalaria tenagophila to infection by A. costaricensis was also determined. One population was genetically selected for the susceptibility to S. mansoni while the other was not. Third-stage larvae were recovered from the snails 30 days after exposure of the two populations to 120 first-stage larvae. All the mollusks were infected. However, a significantly higher number of third-stage larvae were recovered in mollusks not genetically selected.

Angiostrongylus↗

PubMed2003

New intermediate hosts in the life cycle of Zygocotyle lunata in South America.

Biomphalaria peregrina was found to be naturally infected with cercariae of Zygocotyle lunata in a pond of the Zoological Garden of Buenos Aires. Mice and chicks were fed metacercariae and gravid adults recovered. Eggs recovered from mice feces were used for experimental infections. Laboratory-reared B. peregrina and 4 other Biomphaluria spp. were successfully infected with Z. lunata miracidia. Biomphaleria glabrata was refractory. Species of Helisoma, the only intermediate hosts of Z. lunata so far reported, have never been found in Argentina. Species of Biomphalaria may be intermediate hosts of Z lunata in the southern region of the Parana River Basin.

Animals↗

PubMed2004

[Urban schistosomiasis in Cameroon: a longitudinal study of its transmission in a new site of an extension of the intestinal schistosomiasis focus in Mélen, Yaoundé].

In order to to set up the present situation on schistosomiasis in the neighbourhoods around the University of Yaounde I campus, a malacological survey (collection of freshwater snails, their identification and tests on cercarial emergence) was carried out monthly over 12 months in 2 water sources, followed by a parasitological diagnosis of intestinal schistosomiasis in subjects who acknowledge having come into contact with the infested water course. The malacological survey revealed 4 freshwater gastropod species, two (Bulinus globosus and Biomphalaria pfeifferi) of which are intermediate hosts of schistosomes. Biomphalaria pfeifferi specimens from the former quarry pond of Ngoa-Ekellé neighbourhood showed an average infestation rate of 9.7%, and emitted schistosome cercariae throughout the whole period of study The parasitological diagnosis included 112 (81.2%) out of the 138 individuals identified, including 55 males and 57 females; 27 out of the 112 subjects had S. mansoni eggs in stools, making a prevalence rate of 24.1%. These patients were composed of 21 males and 6 females. The prevalence of S. mansoni is therefore significantly higher in males. The average parasitic load for our sample was 248 eggs/g of stools. It was much higher (384 eggs/g stools) for males (280 eggs/g stools) than for females (136 eggs/g stools). The differences of prevalences and parasitic loads between sex can be explained in part by the varying activities of interest according to the different groups in the infested watering places.

Adolescent↗

PubMed1991

Inhibition of lactate dehydrogenase isoenzyme associated with anaerobic respiration in schistosomiasis intermediate host snails.

Lactate dehydrogenase isoenzyme (LD5) which is associated with anaerobic respiration was inhibited to a certain degree in Biomphalaria alexandrina snails, the intermediate host for Schistosoma mansoni. Urea and thiourea were used as inhibitors. The effect of LD5 inhibition on the mortality rate of infected Biomphalaria alexandrina snails and on the susceptibility of the snails to the trematode infection was also studied.

Anaerobiosis↗

PubMed1991

[Epidemiology of intestinal schistosomiasis with Schistosoma mansoni in Richard-Toll (Delta of the Senegal River). Malacological study].

A recent outbreak of intestinal schistosomiasis (1989) has been reported in Richard-Toll (Delta of Senegal River) with a global prevalence of 43%. A malacological survey has been carried in order to study, the density of Biomphalaria pfeifferi the intermediate hosts, their distribution and rate of infection, and to identify the transmission sites. Ten districts have been selected. The snails have been collected in the different water points of these localities which are the river, the Taouey marigot, the Taouey channel and the irrigation channels and drains of the CSS (Senegal Sugar Company). A total of 1,210 Biomphalaria have been collected in 45 sites with a variable density of 2 to 150 snails. The overall rate of infestation of snails is 44% but varies according to the districts (9 to 64%). The transmission is acting in all the districts mainly in the Taouey channel (28% of infested snails) the Taouey marigot (38% of infested snails) and particularly in the channels of CSS (47% of infested snails). The situation is alarming and requires urgent action be undertaken to decrease the prevalence and reduce the transmission.

Animals↗

PubMed1991

The intensity of Schistosoma mansoni in the fishing villages of Bugonga and Kitubulu in Entebbe Peninsula, Uganda.

The intensity of Schistosoma mansoni infection in the fishing villages of Bugonga and Kitubulu, and the occurrence of snail intermediate host population in the two villages are described and compared. A total of five hundred and six faecal samples from both villages were examined by modified Kato's technique and the prevalence infection rate at Kitubulu was 40.3% with mean egg count of 187 eggs per gram(epg) while in Bugonga it was 32.4% and 126 epg respectively. The snail intermediate host for S. mansoni in the two villages was 2,750 Biomphalaria choanomphala at Kitubulu and 1,268 at Bugonga. But at Kitubulu in the vicinity of the village 185 Biomphalaria peifferi occurred in small localized population. The cercarial screening test conducted on 4,018 B. choanomphala and 185 B. peifferi from the two villages revealed higher snail infection rate for both mammalian and non-mammalian cercariae at Kitubulu than Bugonga. Variations in infection rates both among the inhabitants and host snail populations in the two villages are discussed.

Adolescent↗

PubMed1988

Schistosomiasis in Kano State, Nigeria. I. Human infections near dam sites and the distribution and habitat preferences of potential snail intermediate hosts.

Stool and urine samples from 813 schoolchildren and adults from the Tomas and Rimin Gado dam areas of Kano State, Nigeria, showed Schistosoma haematobium to be present at both localities with prevalences of 26.6 and 36.8%, respectively. No cases of S. mansoni were found. The prevalence and intensity of S. haematobium was low and similar in both study areas. Statistical analysis revealed a correlation between prevalence and location, but no evident association with professed patterns of water contact. Investigation of 165 freshwater habitats throughout the state revealed the presence of a number of potential snail intermediate host species, namely Bulinus senegalensis, B. forskali, B. globosus, B. rohlfsi and Biomphalaria pfeifferi. The most widespread species was Bulinus senegalensis, which inhabited shallow pools and excavations on a variety of substrata. Its habitats were typically devoid of aquatic vegetation and included those with highly turbid waters and conductivities as low as 11 microseconds. Bulinus forskali was by contrast relatively rare, occurring in more permanent water courses, although it was often found in mixed populations with B. senegalensis. Bulinus globosus also occurred in seasonally rainfilled pools, but was confined to areas south of the 12 degrees N parallel, and its habitats tended to have a well-developed aquatic flora and clear water. The dominant species in man-made lakes was B. rohlfsi, which occurred in both the Tomas and Rimin Gado reservoirs. Biomphalaria pfeifferi was also primarily lake dwelling, although all species save B. senegalensis were found in irrigation canals.

Adolescent↗

PubMed1978

[An epidemiological study of foci of S. mansoni bilharziosis in Minkana and Nalassi (Lekie Division, Cameroun) (author's transl)].

The epidemiological survey involved the examination of the total population of the two villages as well as the investigation of the freshwater snails in the neigbouring waters bodies. Biomphalaria camerunensis and Biomphalaria pfeifferi were found to be the intermediate hosts of Schistosoma mansoni. The cassage of eggs in the stools was more frequently observed in two groups, those aged 10-19 years and in the elderly women. The study of the prevalence of the disease by means of the indirect immunofluorescence technique on frozen sections of S. mansoni revealed that already in childhood the percentage of subjects with circulating antibodies is high. This percentage remains elevated in subsequent age groups. The geometrical mean reciprocal titers show an age and sex pattern similar to that found for prevalence. Both the percentage of positive indirect immunofluorescence tests and their respective titers were higher in patients with eggs in their stools. The immunological reaction using homologous S. mansoni antigen is more sensitive than that with heterologous S. haematobium antigen.

Adolescent↗

PubMedDate not supplied

Investigation of molluscicidal activity of certain Sudanese plants used in folk-medicine. I. A preliminary biological screening for molluscicidal activity of certain Sudanese plants used in folk-medicine.

A preliminary biological screening for molluscicidal activity of certain Sudanese plants used in Folk-medicine was carried out. 78 samples belonging to 51 species, 45 genera and 28 families were screened. The aqueous extracts of 18 samples belonging to 8 species, 6 genera and 5 families were found to be active against Bulinus truncatus and 7 of these were also found to be active against Biomphalaria pfeifferi. Successive extraction of the 18 active samples with petroleum ether, ethanol and water showed that the petroleum ether extracts of only 4 samples were active against Bulinus truncatus; while the alcoholic extracts of 16 samples were found to be active against the same snail species. Only the alcoholic extracts of 4 samples were proved to be active against Biomphalaria pfeifferi. In the successive extraction technique, only the aqueous extract of Gardenia vogelii fruit pulp was proved to be active against the two snail species tested.

Acacia↗

PubMedDate not supplied

[Method for the individual maintenance of mollusks infected with Schistosoma larvae in a thermostatic apparatus].

A technique has been suggested for individual maintenance of intermediate hosts of Schistosoma mansoni, molluscs of the genus Biomphalaria, in thermostat water bath with thermoregulator in order to study the host-parasite relationships in the mollusc-trematode system. Advantages of the suggested technique have been shown for studying total production of Cercaria when estimating the compatibility degree of various strains of S. mansoni and races of molluscs of some species of the genus Biomphalaria.

Animals↗

PubMedDate not supplied

[Study of the distribution of schistosomiasis mollusks intermediate hosts in west africa. First results (author's transl)].

During 18 surveys carried out in 29 regions of 6 West african countries (Benin, Ivory Coast, Upper Volta, Mali, Niger and Togo), one species of Biomphalaria (Biomphalaria pfeifferi) and six species of Bulinus (Bulinus truncatus rohlfsi, B. globosus, B. jousseaumei, B. umbilicatus, B. senegalensis and B. forskalii) were collected. First indications of the distribution of these species demonstrated: the presence of 3 principal species (B. pfeifferi, B. globosus and B. truncatus rohlfsi); the absence of B. pfeifferi, above latitude 14 degrees north; the presence of a zone of B. truncatus rohlfsi in the north, a zone of B. globosus in the south and an intermediate zone where these two species are sympatrie; the possible presence of two strains of Schistosoma haematobium, each being transmitted by only one of the two preceding intermediate hosts. The authors point out that the parasitic diseases and their intermediate hosts are extending, as a result of the various hydraulic works and insist that the authorities should be duly made aware of the health problems generated by any development project.

Africa, Western↗

PubMed1994

[Distribution of intermediate mollusc hosts in human schistosomiasis in the Office of Niger (Mali).II. Role of different habitats in the transmission].

To determine the role of habitats in the schistosomiasis transmission all the year, a study on snail hosts distribution was carried out within various parts in the irrigated system of the "Office du Niger". Bulinus truncatus and Biomphalaria pfeifferi were the only snail hosts recorded. Densities were low and 85% (46/54) of breeding sites contained less than 50 snails collected per man/hour. Primary and secondary canals play the most important role in disease transmission because of the stability of these habitats, the pollution of human water contact by remnants of food and wastes which favourised the snail growth and infestation. Prevalences were 23.3% (46/197) in Bulinus truncatus and 2.5% (6/243) in Biomphalaria pfeifferi. The cercariae shedding was permanent, but the infection varied significantly according to the snail species, the period and to the area.

Animals↗

PubMed1993

Effect of rice cultivation on the prevalence and infection rates of Schistosoma intermediate host.

In this study, it was aimed to explore the effect of rice cultivation on the prevalence, density and infection rates on the snail intermediate hosts of human schistosomiasis. A village was chosen and examine for the main water canal supplying the rice field by making three successive scoops at 10.20, 30, 40 and 50 meters up stream the site of the pump supplying the rice field. The same was done in the large irrigation canal supplying 50 feddans of rice up to 100 meters (i.e. 10 sampling sites). Also the drains in between the rice fields were examined at 10 meters distance throughout the drain. The hunted snails were sorted, the Biomphalaria alexanderina and Bulinus truncatus were separated, their age was determined then crushed to look for immature stages under the microscope. Also the vegetations coming in the scoops were examined. The results showed that rice cultivation and irrigation is a suitable site for the prevalence and intensity of snails. Both species of snails were found in the main canal, irrigation canal and drains. All Bulinus truncatus snails were free from infections. The number of infected Biomphalaria alexanderina snails was significantly higher in the irrigation canal and drains than main canal which may be attributed to pollution of the drain water and irrigation canal by micturition and defecation or to the use of water in ablution.

Animals↗

PubMedDate not supplied

[Lymnic snails from the microregion of Belo Horizonte, Minas Gerais, Brazil with an emphasis on parasite disease vectors].

A malacological survey to detect foci of transmission of schistosomiasis and other parasitic diseases was undertaken into water-courses from 13 municipalities of microregion of Belo Horizonte, MG, Brazil. From 1990 to 1996, 22,066 snails were collected. From those, 378 (1.7%) were found infected by trematodes: Biomphalaria glabrata (7,920), infected by Schistosoma mansoni (1.9%), Echinostomatidae (1.2%), Strigeidae (0.6%), Cercaria minense (0.1%) and Derogenidae (-0.1%); B. straminea (4,093) infected by Strigeidae (0.6%), Echinostomatidae (0.2%), Clinostomatidae (-0.1%) and two unidentified cercariae; B. tenagophila (1,338), infected by Strigeidae (0.1%) and Physa marmorata (1,776) by Echinostomatidae (1.6%). The snails Biomphalaria peregrina, B. occidentalis, B. schrammi, Drepanotrema depressissimum, D. lucidum, D. cimex, Physa cubensis, Lymnaea columella, Melania tuberculata, Idiopyrgus souleyetianus, Pomacea sp, Anodontites sp and Ancylidae were found noninfected. Snails from 9 municipalities were infected by S. mansoni and from 11 by other trematodes.

Animals↗

PubMed1987

The phospholipid and fatty acid composition of Schistosoma mansoni and of its purified tegumental membranes.

The lipid compositions of mature male and female Schistosoma mansoni and cercariae were compared to that of the hepato-pancreas of unparasitised Biomphalaria globrata (the intermediate snail host), and of red blood cells and sera of hamsters (the mammalian host). Membranes were isolated from the tegument of mature schistosomes by spontaneous release into phosphate-buffered saline, with or without vortexing, and by removal from the parasite's surface using poly-lysine beads. The phospholipid composition of the membranes prepared by the three methods showed a typical plasma membrane-like profile, with high sphingomyelin content (approximately 20%) and cholesterol to phospholipid molar ratio (0.7-1.1). The fatty acid compositions of the resolved phospholipid classes were analysed. Although the composition was in general unremarkable, a high content of eicosaenoic acid (20:1), rarely found in mammals, was noted in whole schistosomes, cercariae, the hepato-pancreas of unparasitised Biomphalaria, and the isolated tegumental membranes. Eicosaenoic acid was also found in adults of Schistosoma japonicum. Host serum lipids from normal and parasitised hamsters contained extremely low amounts of eicosaenoic acid, indicating that this fatty acid is probably continually synthesised by the parasite, probably from preformed fatty acid precursors provided by the host.

Animals↗

PubMed2002

A phylogeny of planorbid snails, with implications for the evolution of Schistosoma parasites.

The Planorbidae represent one of the most important families of freshwater snails. They have a wide distribution and are significant both medically and economically as intermediate hosts for trematode worms. Digenetic trematodes of the genus Schistosoma cause schistosomiasis, a disease that infects 200 million people, and domestic animals throughout the tropics. Three of the four recognized species groups of Schistosoma rely on snails of the family Planorbidae to complete their life cycles. Each species group requires a specific planorbid genus-Bulinus, Biomphalaria, or Indoplanorbis. Our understanding of the relationships among the genera within the Planorbidae is rudimentary and based solely on internal anatomy and shell morphology. Two molecular markers, ribosomal 28S and actin exon 2, were sequenced and a phylogeny constructed for 38 taxa representing 16 planorbid genera. The phylogeny supports the division of the Planorbidae into two subfamilies, the Bulininae and Planorbinae. Interestingly, two representatives of the family Ancylidae fall within the Planorbidae highlighting the need for further analysis and possible reclassification of this group. A molecular based phylogeny of the genus Schistosoma was then mapped against the snail tree. The trees indicate that planorbid-transmitted Schistosoma appear not to be co-speciating with their current snail host lineages. Rather, host switching was prominent, including a switch involving two distantly related planorbid genera, Biomphalaria and Bulinus. Our study of the Planorbidae poses fundamental questions regarding how and when Schistosoma acquired new snail hosts, including how switches to relatively distant hosts are accomplished and why some available planorbids were not colonized.

Actins↗

PubMed2001

Infection induces antibodies against the cercarial secretions, but not against the cercarial elastases of Schistosoma mansoni, Schistosoma haematobium, Schistosoma japonicum and Trichobilharzia ocellata.

Cercarial secretions from different species of the parasite Schistosoma and from Trichobilharzia ocellata contain a proteolytic activity, cercarial elastase, which was demonstrated by a 30 kDa band in gelatin gels. Sera of patients infected with Schistosoma mansoni, Schistosoma haematobium or Schistosoma japonicum contain immunoglobulin G which react in ELISA with cercarial secretions from all schistosomes and cross-react among the different parasite species. In Western blots, however, infection sera from patients, as well as heavily infected mice or rabbits, did not react with a 30-kDa protein. Moreover, when sections from infected snails (Biomphalaria, Bulinus and Lymnaea) were analysed by immunofluorescence using the same infection sera, only the tegument of the developing cercariae was recognized, but not the acetabular glands. In contrast, when antisera against purified cercarial elastase from either S. mansoni or S. haematobium were tested with sections of infected Biomphalaria or Bulinus, fluorescence was strong in the preacetabular glands of the cercariae of either species, but undetectable with the tegument. Cross-reactivity of both antisera extended to T. ocellata-infected Lymnaea, but not to S. japonicum-infected Oncomelania. In conclusion, although immunization with purified cercarial elastase results in antibody production, the enzyme does not induce an apparent antibody response following natural infection.

Animals↗

PubMed1977

Agglutinins and lysins in the molluscan family Planorbidae: a survey of hemolymph, egg-masses, and albumen-gland extracts.

1. Thirty-one strains representing eight species and four genera of the molluscan family Planorbidae were surveyed for the presence of hemagglutinins and hemolysins. Extracts prepared from albumen-glands and egg-masses, as well as hemolymph, were assayed by a micro-hemagglutination technique in which human erythrocytes were used as receptors. 2. Hemagglutinins and hemolysins for human erythrocytes were not uniformly present in all members of the family and detection of these substances depended, in part, on the material tested. 3. Neither heating to 56 degrees C, dialysis, storage at -20 degrees C for up to a year, nor repeated freezing and thawing appeared to effect the agglutinating activity of egg or albumen-gland extracts. 4. Inhibition of the agglutinating activity of Helisoma hemolymph could be accomplished with N-Acetyl-D-Galactosamine, but this sugar had no effect on the activity of Biomphalaria agglutinins. 5. There is evidence to suggest that the source and nature of agglutinins from Helisoma and Biomphalaria species are different. 6. Lectins may be of some value in characterizing snail populations and as an aid in the taxonomic discrimination of species.

Agglutinins↗