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PubMed2000

Toxic activities of the plant Jatropha curcas against intermediate snail hosts and larvae of schistosomes.

The aim of studies on plant molluscicides is to complement methods for controlling snails acting as intermediate hosts of schistosomes. We report on the toxic activity of extracts from Jatropha curcas L. (Euphorbiaceae) against snails transmitting Schistosoma mansoni and S. haematobium. We studied different extracts' effects on infectious larvae, cercariae and miracidia of S. mansoni. Compared to aqueous extract, methanol extract showed the highest toxicity against all tested organisms with LC100-values of 25 p.p.m. for cercariae and the snail Biomphalaria glabrata and 1 p.p.m. for the snails Bulinus truncatus and B. natalensis. Attenuation of cercariae leading to reduced infectivity in mice could be achieved in concentrations below those exerting acute toxicity. In view of our results and the ongoing exploitation of J. curcas for other purposes, this plant could become an affordable and effective component of an integrated approach to schistosomiasis control.

Animals↗
PubMed2003

Ecological and molecular studies on emerging schistosomiasis mansoni in Dhofar Governorate, Sultanate of Oman.

The recent detection of some cases of autochtonous schistosomiasis mansoni in Dhofar, Oman, prompted a search for the transmission sites. The five field surveys we conducted from November 2000 to February 2002 provided ecological data on schistosomiasis in Dhofar. Twenty-eight water bodies situated within 8-160 km from Salalah, the largest city of Dhofar and at altitudes of up to 900 m, were surveyed for freshwater snails. Biomphalaria arabica was found in 15 of them. Three sites (Tibraq, Siginitti and Arazat) had Schistosoma infected snails, the first snails shedding cercariae of this parasite ever collected in Oman. The parasite from Dhofar was analysed by Random Amplified Polymorphic DNA comparisons using 11 primers and 167 polymorphic fragments and had 87-88% similarity with Schistosoma mansoni from Guadeloupe, but only 37-38% similarity with S. rodhaini from Burundi. Thus, it is a strain of S. mansoni. During the November 2000 survey, the prosobranch snail Melanoides tuberculata was associated with B. arabica in 10 of the 13 B. arabica sites. Cercariae from other species of Digenea emerged from five of the B. arabica sites, including the three named above. This paper presents the first finding of S. mansoni in the Dhofar Governorate and represents an initial study of the biology of S. mansoni transmission. This parasite and its cycle need further biological and molecular characterization, and the clarification of its epidemiological status in Dhofar Governorate is an urgent task.

Animals↗
PubMedDate not supplied

[Natural transmission of Schistosoma mansoni in Guadeloupe (French Antilles). Preliminary note (author's transl)].

Occasioning in Guadeloupe a high rate of morbidity, schistosomiasis is unequally spread in the field. The intermediate host, Biomphalaria glabrata, is wide-spread. But some biotopes only, most of them located on the coast belt of the montainous island, allow the parasite growth. Among them, the irrigation canals appear as the most dangerous source of contamination for human population.

Animals↗
PubMed1984

[Activities of a Schistosoma mansoni focus of transmission in Martinique (French Antilles)].

A focus of intestinal schistosomiasis was discovered in november 1981 in Martinique in the Saint-Pierre area. An analysis of its structure and of the mecanisms of the transmission of the parasite was carried out between 1981 and 1983. This focus presents the following particularities: a transmission site very small constituted by water cress beds; a small human population infected with a prevalence of 13% (positive stools) to 41,3% (positive serologies); a weak fecal contamination of the water; a non functioning sewage stabilization tank is responsible for this contamination; a rich population of the snail host Biomphalaria glabrata (40,5 to 256,3 Bg/m2) with a low prevalence of infestation (0,13 to 0,59%); low cercarial densities in the water cress bed waters; a very low contamination of the Roxelane river water in to which the water from the water cress beds flows. The epidemiological importance of this contamination has proved very low but not altogether absent. This focus appears as a particular case in Martinique because all the surveys which have been conducted in the island to date has not uncovered a similar example.

Animals↗
PubMed1985

[Factors responsible for preventing the carrying out of the Schistosoma mansoni cycle in the waters of Grande Terre of Guadeloupe (French Antilles)].

Different surveys which have been conducted in ponds and pools in the Grande Terre of Guadalupe, have demonstrated the absence of Schistosoma mansoni transmission in spite of apparent favourable ecological conditions. Four hypothesises can explain this absence of transmission: 1 - the presence of Biomphalaria glabrata populations non-susceptible to the infestation by S. mansoni. 2 - Ecological conditions unfavourable to the survival of parasitized snails. 3 - Ecological conditions unfavourable to the production, survival and infectivity of the S. mansoni cercariae. 4 - Factors causing the non-contamination of the snails. The results show that the transmission of schistosomiasis mansoni is possible in the ponds and pools of Grande Terre. Only human behaviour is responsible for the absence of actual transmission in the waterbodies of this area. Man breaks the life-cycle of the parasite by avoiding all fecal pollution and therefore all snail contamination.

Animals↗
PubMed1999

In vitro culture of rediae of Echinostoma caproni.

Rediae of Echinostoma caproni (Egyptian strain) were dissected from Biomphalaria glabrata snails at intervals from 13-34 days post-exposure and co-cultured for up to 51 days with cells of the B. glabrata embryonic (Bge) cell line. Rediae readily ingested Bge cells and survived longer when co-cultured with cells than in cell-free cultures. Rediae released mostly motile cercariae throughout the observation period when in Bge medium and cells. Rediae cultured in 199 medium with Bge cells also produced progeny throughout most of the observation period. In the latter medium, progeny were much more likely to include rediae as well as cercariae. Some cercariae produced in vitro encysted as metacercariae. Rediae consumed cercariae released into culture but were not observed to attack one another or rediae of a different echinostome species.

Animals↗
PubMed1994

Antibacterial and molluscicidal phenolic acids from Spondias mombin.

Spondias mombin L. (Anacardiaceae), used in traditional medicine because of its antimicrobial properties, was found to contain a series of 6-alkenyl-salicylic acids. They were isolated from the ethanolic extract of leaves and stems of Spondias mombin by a combination of chromatographic methods. Their structure was determined by NMR and MS techniques as (17:3), (17:2) and (17:1) pelandjuaic acid [or 6-(8'Z,11'Z,14'Z-heptadecatrienyl)-salicylic acid, 6-(8'Z,11'Z-heptadecadienyl)-salicylic acid, and 6-(10'Z-heptadecenyl)-salicylic acid, respectively], 6-(12'Z-non-adecenyl)-salicylic acid, and 6-(15'Z-heneicosenyl)-salicylic acid, the two last compounds being new ones. These phenolic acids were shown to have a pronounced antibacterial effect against Bacillus cereus, Streptococcus pyogenes, and Mycobacterium fortuitum (minimal bactericidal concentration in a concentration range of 3-25 micrograms/ml), and a molluscicidal effect against the snail Biomphalaria glabrata, an intermediate host in the schistosome life cycle. Because of their high molluscicidal activity (LC90 down to 1-3 ppm), these long-chain salicylic acid derivatives may be important tools in the prevention of schistosomiasis.

Animals↗
PubMed1990

Molluscicidal and antischistosomal activities of Zingiber officinale.

Experiments were conducted to study the major constituents of Zingiber officinale responsible for its molluscicidal activity and the effect of the active component on different stages of Schistosoma mansoni. Gingerol and shogaol exhibited potent molluscicidal activity on Biomphalaria glabrata. Gingerol (5.0 ppm) completely abolished the infectivity of Schistosoma mansoni miracidia and cercariae in B. glabrata and mice, respectively, indicating that the molluscicide is capable of interrupting schistosome transmission at a concentration lower than its molluscicidal concentrations.

Animals↗
PubMed1990

Molluscicidal properties of constituents from the liverwort Ricciocarpos natans and of synthetic lunularic acid derivatives.

Five new sesquiterpenoids, three monocyclofarnesane, and two cuparane derivatives, isolated from the liverwort Ricciocarpos natans (L.) Corda have been tested against Biomphalaria glabrata, one of the snail vectors of schistosomiasis (bilharzia). Molluscicidal activity is exhibited by four of the sesquiterpenoids with an LC100 of 11 ppm of the most toxic compound. Lunularic acid, a common growth inhibitor of liverworts, and five of its synthetic derivatives have also been tested, and two derivatives were found to be highly active.

Animals↗
PubMed1992

Molluscicidal constituents of Calophyllum from Madagascar: activity of some natural and synthetic neoflavonoids and khellactones.

Crude extracts of seeds, leaves and barks of four Madagascan Calophyllum species: C. inophyllum, C. recedens, C. chapelieri, and C. verticullatum, have been tested for molluscicidal activity against Biomphalaria glabrata. All seed extracts showed significant activity. The major constituents of the most active Calophyllum species were examined. Some related coumarinic derivatives were synthesized in order to improve the biological activity. Among the compounds prepared, 5,7-dihydroxy-6-(2-methylbutyryl)-4-phenyl-coumarin presented an interesting molluscicidal activity.

Animals↗
PubMed1992

The molluscicidal activity of coumarins from Ethulia conyzoides and of dicumarol.

The molluscicidal principles of Ethulia conyzoides were identified as ethuliacoumarin A (1) and isoethuliacoumarin A (2). Ethuliacoumarin A possessed an LC90 between 19 and 23.5 ppm depending on the age of the snail against Biomphalaria glabrata, and between 12 and 15 ppm against Bulinus truncatus. In addition, ethuliacoumarin A was found to be cercaricidal at 25 ppm and ovicidal. Ethuliacoumarin has the structural requirements considered essential for anticoagulant activity. Consequently the anticoagulant dicumarol (4) was tested and found to be molluscicidal in the range from 2.5 to 10 ppm. In contrast, the coumarin anticoagulant warfarin (3) did not show molluscicidal activity.

Animals↗
PubMed2006

Red blood with blue-blood ancestry: intriguing structure of a snail hemoglobin.

The phylogenetic enigma of snail hemoglobin, its isolated occurrence in a single gastropod family, the Planorbidae, and the lack of sequence data, stimulated the present study. We present here the complete cDNA and predicted amino acid sequence of two hemoglobin polypeptides from the planorbid Biomphalaria glabrata (intermediate host snail for the human parasite Schistosoma mansoni). Both isoforms contain 13 different, cysteine-free globin domains, plus a small N-terminal nonglobin "plug" domain with three cysteines for subunit dimerization (total M(r) approximately 238 kDa). We also identified the native hemoglobin molecule and present here a preliminary 3D reconstruction from electron microscopical images (3 nm resolution); it suggests a 3 x 2-mer quaternary structure (M(r) approximately 1.43 MDa). Moreover, we identified a previously undescribed rosette-like hemolymph protein that has been mistaken for hemoglobin. We also detected expression of an incomplete hemocyanin as trace component. The combined data show that B. glabrata hemoglobin evolved from pulmonate myoglobin, possibly to replace a less-efficient hemocyanin, and reveals a surprisingly simple evolutionary mechanism to create a high molecular mass respiratory protein from 78 similar globin domains.

Amino Acid Sequence↗
PubMed1992

Immunosuppression in the definitive and intermediate hosts of the human parasite Schistosoma mansoni by release of immunoactive neuropeptides.

Evidence supporting the concept that the parasitic trematode Schistosoma mansoni may escape immune reactions from its vertebrate (man) or invertebrate (the freshwater snail Biomphalaria glabrata) hosts by using signal molecules it has in common with these hosts was obtained by the following experiments. The presence of immunoactive proopiomelanocortin (POMC)-derived peptides [corticotropin (ACTH), beta-endorphin] in, and their release from, S. mansoni was demonstrated. Coincubation of adult worms with human polymorphonuclear leukocytes or B. glabrata immunocytes led to the appearance of alpha-melanotropin (MSH) in the medium. The conclusion that this alpha-MSH resulted from conversion of the parasite ACTH by neutral endopeptidase 24.11 (NEP) present on these cells was supported by the fact that the alpha-MSH level in the medium was markedly reduced by addition of the specific NEP inhibitor phosphoramidon. This interpretation is substantiated by the fact that no conversion was observed in comparable tests with human monocytes, which exhibit no NEP activity. alpha-MSH has the capacity to inactivate formerly active immunocytes not only from the definitive host (man, hamster) but also from the intermediate host (B. glabrata), as determined by microscopic computer-assisted examination of conformational changes. POMC-derived peptides have been detected in B. glabrata hemolymph 2, 10, and 24 days after infection by S. mansoni miracidia. Immunocytes from infected snails were found to be inactivated, and this inactivation was prevented by antibodies directed against ACTH and alpha-MSH. The immunoactive beta-endorphin released from S. mansoni does not appear to be subject to enzymatic conversion. Since it is active at lower concentrations, it may be used for distant signaling.

Adrenocorticotropic Hormone↗
PubMed1997

A family of fibrinogen-related proteins that precipitates parasite-derived molecules is produced by an invertebrate after infection.

After infection with the digenetic trematode Echinostoma paraensei, hemolymph of the snail Biomphalaria glabrata contains lectins comprised of 65-kDa subunits that precipitate polypeptides secreted by E. paraensei intramolluscan larvae. Comparable activity is lacking in hemolymph of uninfected snails. Three different cDNAs with sequence similarities to peptides derived from the 65-kDa lectins were obtained and unexpectedly found to encode fibrinogen-related proteins (FREPs). These FREPs also contained regions with sequence similarity to Ig superfamily members. B. glabrata has at least five FREP genes, three of which are expressed at increased levels after infection. Elucidation of components of the defense system of B. glabrata is relevant because this snail is an intermediate host for Schistosoma mansoni, the most widely distributed causative agent of human schistosomiasis. These results are novel in suggesting a role for invertebrate FREPs in recognition of parasite-derived molecules and also provide a model for investigating the diversity of molecules functioning in nonself-recognition in an invertebrate.

Amino Acid Sequence↗
PubMed2000

Schistosome invasion of human skin and degradation of dermal elastin are mediated by a single serine protease.

Aquatic larvae (cercariae) of the trematode parasite Schistosoma mansoni rapidly penetrate human skin by degrading host proteins including elastin. Two serine proteases, one chymotrypsin-like and the second trypsin-like, have been proposed to be involved. To evaluate the relative roles of these two proteases in larval invasion, both were purified, identified by sequence, and then biochemically characterized. The trypsin-like activity was resolved into two distinct serine proteases 76% similar in predicted amino acid sequence. Southern blot analysis, genomic polymerase chain reaction, and immunolocalization demonstrated that the trypsin-like proteases are in fact not from the schistosome, but are released with larvae from the snail host Biomphalaria glabrata. Invasion inhibition assays using selective inhibitors confirmed that the chymotrypsin-like protease is the enzyme involved in skin penetration. Its ability to degrade skin elastin was confirmed, and the three sites of cleavage within elastin help define a new family of elastases.

Amino Acid Sequence↗
PubMed2002

Larval trematode infections in freshwater snails from the highveld and lowveld areas of Zimbabwe.

Between November 1998 and October 2000, freshwater snails were collected monthly from the highveld and lowveld areas of Zimbabwe to determine the occurrence of larval trematodes. A total of 13,789 snails, representing ten species, were collected from 21 sites and 916 (6.6%) harboured patent trematode infections. Eight morphologically distinguishable types of cercariae were identified. Bulinus tropicus had the highest overall prevalence of infection (13.1%). The echinostome was the most common type of cercaria recovered, contributing 38.2% of all infections. Schistosoma cercariae were recovered mainly from the highveld and comprised 8.0% of all infections. Amphistome cercariae contributed 37.6% of all infections and were recorded from both the highveld and lowveld areas with a peak prevalence occurring during the post-rainy period (March-May). The main intermediate host for amphistomes was B. tropicus. Infections in B. globosus, B. forskalii and Biomphalaria pfeifferi with amphistome cercariae are new records for Zimbabwe.

Animals↗
PubMed2005

Cercarial tail loss in Echinostoma caproni: the influence of in vivo encystment and copper sulphate.

Echinostoma caproni tail loss was studied in vitro in the presence of the toxicant copper sulphate (CuSO4) in concentrations ranging from 1 to 10 000 mg l(-1) in standardized artificial spring water (pH 7.4, osmolarity 34 mOsm kg(-1) H2O, Ca(2+) 20 mg l(-1)) at 23 degrees C. Tail loss was also studied in the absence of toxicants during in vivo encystment of the cercariae in juvenile Biomphalaria glabrata. As the concentration of CuSO4 increased, the percentage of cercarial tail loss increased. By 2 h in 10 000 mg l(-1), 1000 mg l(-1) and 100 mg l(-1) CuSO4, 50%, 23% and 13%, respectively, of the cercariae had lost their tails. In the in vivo studies, by 1 h PI, 59+/-5% of cercariae had lost their tails and only 4+/-1% of the cercariae were actively swimming in the multi-well dishes. At 3 h PI, 72+/-3% of the cercariae began to form cysts within the snails.

Animals↗