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PubMed1992

Cultivation of excysted metacercariae of Echinostoma caproni to ovigerous adults in the allantois of the chick embryo.

Chemically excysted metacercariae of Echinostoma caproni inoculated into the allantois of domestic chick embryos became ovigerous in that site within 9 days postinoculation. The egg preparation technique of Saville and Irwin was markedly better than that of a modified Zwilling procedure for obtaining large numbers of postinoculation embryos with worm infections. Adults of E. caproni from the allantois were larger and became ovigerous sooner than worms grown on the chorioallantois. Only worms from the allantois produced eggs with fully developed miracidia. Miracidia were released from these eggs, but an insufficient number was available to attempt infections in Biomphalaria glabrata snails.

Allantois↗
PubMed2003

Correlation between snails and fish in fish ponds of World Fish Center (ICLARM) with special reference to snail vectors of schistosomiasis and fascioliasis.

The abundance of snail species in earthen fish ponds, irrigation and drainage canals at World Fish Center (ICLARM) in descending order was Bellamya unicolor (50.89%) > Physa acuta (18.94%) > Cleopatra bulimoides (7.6%) > Lanistes carinatus (6.73%) > Bulinus truncatus (5.19%) > Melanoides tuberculata (4.83%) > Lymnaea natalensis (3.14%) > Gabbiella senaariensis (0.9%) > Biomphalaria alexandrina (0.55%) > Lym naea truncatula (0.4%) > Planorbis planorbis and Succinea cleopatra (0.33%) > Ferrissia isseli (0.18%). Dead snails constituted about 5.19% of all the collected specimens. There were dramatic decrease in the total number of pulmonates in fish ponds which contained only Tilapia sp., and a very small number of cat fish, whereas the numbers of prosobranchia snails were much higher in these ponds. In fish ponds which accommodated a variety of fish species, the most dominant snail was B. unicolor followed by L. carinatus. However, pulmonate snails were absent in these ponds. B. truncatus was the only snail species found in concrete tank which contained only young tilapias with a very small size (5-8 cm in standard length). In irrigation canals, the number of snails and diversity was much higher than those in fish ponds. Out of 191 snails collected from inlet irrigation canal, 71 were dead, but in the outside irrigation canals, seven out of 564 snails were dead. P. acuta was absent in all examined fish ponds, but it was alive and in a high number (497 snails) in the outside irrigation canals. The number of snails collected from Bahnasawy drain was remarkably low (128 snails), however the diversity of snails was much higher compared to those in fish ponds and irrigation canals. Snail populations were stable with constant recruitment of young to adult snails for all the studied species.

Animals↗
PubMed2004

[Epidemiology of schistosomiasis mansoni in a low endemic area].

We discuss the epidemiological patterns of schistosomiasis mansoni in areas with low transmission in Brazil. We define as areas of low endemicity those where the prevalence is less than 10%, the number Schistosoma mansoni eggs per gram of feces (epg) is less than 96, and carriers are asymptomatic. Data are from the county of Pedro de Toledo in the Ribeira Valley (São Paulo State) and were collected randomly according to the aggregate pattern of S. mansoni within the hosts. We suggest the replacement of parasitological methods by more sensitive and specific serological techniques. The main risk factor for infection is type of leisure activity. Infection is more frequent in the 10-14, 15-19, and 20-24-year age brackets. Geometric mean epg is 58.5. Intensity of infections correlates well (rs = 0.745) with prevalence. The highest index of potential contamination is in the 5-20-year age bracket (57.6%). Autochthonous cases show close association with Biomphalaria tenagophila, which has a low infection rate (2%). Prevalence, incidence, and intensity of infection patterns are similar to those of moderate and high endemic areas. Social and cultural aspects must be studied in order to obtain a global epidemiological view of schistosomiasis.

English Abstract↗
PubMed2004

[Dynamics of intestinal schistosomiasis in Cameroon: evolution of transmission in the mixed zone of Nkolmébanga, Lékié].

This study was undertaken to evaluate the current status of shistosomiasis in the Nkolmébanga region (Lékié) of Cameroon, previously determined to be a mixed zone harboring both Schistosoma mansoni and S. intercalatum. Study involved both malacology with collection and identification of freshwater snails in four waterpools and parasitology with collection and analysis of stools from schoolchildren. Five species of freshwater snails were identified including two that were intermediate host of Schistosomes, i.e., Biomphalaria pfeifferi and Bulinus forskalii. Only B. pfeifferi species collected from the Momboh and Mbonsoh Rivers shed Schistosoma cercaria. A total of 347 schoolchildren were enrolled but only 200 provided stools for parasitological testing. There were 93 boys and 107 girls. Parisitology demonstrated S. intercalatum eggs in the stools of no children. S. mansoni eggs were identified in the stools of 10 children for a prevalence of 5%. Parasitic load ranged from 24 to 1104 eggs per gram of stool. In this study both malacologic and parasitological findings suggested that S. mansoni persists in Nkolmébanga region but that S. intercalatum has disappeared probably as a result of deforestation and urbanization.

Adolescent↗
PubMed2005

Dispersal in a parasitic worm and its two hosts: consequence for local adaptation.

Characterizing host and parasite population genetic structure and estimating gene flow among populations is essential for understanding coevolutionary interactions between hosts and parasites. We examined the population genetic structure of the trematode Schistosoma mansoni and its two host species (the definitive host Rattus rattus and the intermediate host Biomphalaria glabrata) using microsatellite markers. Parasites were sampled from rats. The study was conducted in five sites of the Guadeloupe Island, Lesser Antilles. Mollusks display a pattern of isolation by distance whereas such a pattern is not found neither in schistosomes nor in rats. The comparison of the distribution of genetic variability in S. mansoni and its two host species strongly suggests that migration of parasites is principally determined by that of the vertebrate host in the marshy focus of Guadeloupe. However, the comparison between genetic differentiation values in schistosomes and rats suggests that the efficacy of the schistosome rat-mediated dispersal between transmission sites is lower than expected given the prevalence, parasitic load and migration rate of rats among sites. This could notably suggest that rat migration rate could be negatively correlated to the age or the infection status of individuals. Models made about the evolution of local adaptation in function of the dispersal rates of hosts and parasites suggest that rats and mollusks should be locally adapted to their parasites.

Animals↗
PubMed2004

Preliminary studies on the prevalence and distribution of urinary schistosomiasis in Ondo State, Nigeria.

The prevalence of S. haematobium infection in 18 Local Government Area (LGA) in Ondo state was determined by examining pupils from randomly selected schools in the state. A total of 4266 urine samples were examined and 1303 (30.5%) were infected with the parasite. The infection was recorded in both rural and urban communities in each LGA. The overall prevalence was significantly higher in males (33.7%) than in females (26.0%) (P = -0.001). The LGA exhibiting the highest overall prevalence of infection was Akure north (86.2%; Cl, 0.82-0.9). The infection was most common in subjects between the ages of 11 and 15 years. Seven species of aquatic snails were encountered and B. (P). globosus was the most abundant and widespread species. The Owena river/dam in Idanre LGA was richest in molluscan fauna. B. (P). globosus and Biomphalaria pfeifferi shedding cercariae were recovered from Owena river and dam. The study shows that there were spatial heterogeneities in the prevalence of infections in both human population and the snail intermediate hosts. The implications of the clustering nature of the disease, for a successful control program in the state, were discussed.

Adolescent↗
PubMed2005

Intraspecific competition and the evolution of virulence in a parasitic trematode.

Intrahost competition between parasite genotypes has been predicted to be an important force shaping parasite ecology and evolution and has been extensively cited as a mechanism for the evolution of increased parasite virulence. However, empirical evidence demonstrating the existence and nature of intraspecific competition is lacking for many parasites. Here, we compared within-host competitiveness between genetic strains of Schistosoma mansoni with high (HIGH-V) or low (LOW-V) virulence to their intermediate snail host, Biomphalaria glabrata. Groups of snails were exposed to either one or the other of two parasite strains, or a mixed infection of both strains, and the resulting progeny were identified using a molecular marker. In two separate experiments investigating simultaneous and sequential infections, we demonstrated that the lifetime reproductive success of parasite strain HIGH-V was reduced in the presence of a faster replicating parasite genotype, LOW-V, regardless of whether it was in a majority or minority in the initial inoculum of the simultaneous exposure or of its relative position in the sequential exposure experiment. Thus, we demonstrate competition between parasite genotypes and asymmetry in competitive success between parasite strains. Moreover, since the less virulent strain investigated here had a competitive advantage, we suggest that a high frequency of multiple infections could favor the evolution of less, rather than more, virulent parasites in this system.

Animals↗
PubMed2004

Common antigenicities between Angiostrongylus cantonensis and various species of snails.

Studies on common antigenicities were carried out by using rabbit sera immunized with Angiostrongylus cantonensis adult worms or the third stage larvae and antigens of various species of snails and vice versa by the immunoblotting technique. The results obtained are summarized as follows: (1) Common antigenicities between A. cantonensis adult worms and snails susceptible to A. cantonensis were observed in a range of molecular weights of 14.3 to 200 kDa. In Puerto Rican pigmented Biomphalaria glabrata and Achatina fulca, which had high infection rates with A. cantonensis, we recognized 15 to 16 bands against the adult worm, especially the band with a molecular weight of 29 kDa, which had a more intense reaction. (2) Common antigenicities between A. cantonensis third stage larvae and snails susceptible to A. cantonensis, were observed in a range of molecular weights of 14.3 to 97.4 kDa, especially A. fulica and B. glabrata, where we detected many bands in molecular weight range of 18.4 to 43 kDa. Based on the common antigenicities between A. cantonensis and snails susceptible to A. cantonensis, it is possible that the common antigenicities are one of the factors defining the different susceptibilities of various species of snails to A. cantonensis, and more bands are seen with increasing infection rates with A. cantonensis. Of those bands, the protein with the molecular weight of 29 kDa may be the main common antigen between the A. cantonensis adult worm, the third stage larvae and the snails susceptible to A. cantonensis.

Angiostrongylus cantonensis↗
PubMed2005

Update of fasciolosis-transmitting snails in Egypt (review and comment).

Several snail species may contribute in transmission of fasciolosis in Egypt. These molluscs show a variable sensibility to natural infections with Fasciola species. Radix natalensis is considered to be the essential intermediate host for F. gigantica based on field and experimental studies. Cercarial production from R. natalensis experimentally infected with F. gigantica is affected by the species of definitive host from which the eggs are obtained, as well as the different laboratory conditions. Another lymnaeid, Galba truncatula, may play a role in transmitting this parasite in Egypt, as it was found naturally infected with F. gigantica. Latter snail species, originated from France, was susceptible to experimental infections with Egyptian miracidia of F. gigantica and it had a cercarial production close to that of local R. natalensis. Two other snails, Pseudosuccinea columella and Biomphalaria alexandrina, were naturally found harboring larvae of Fasciola sp. At the level of intermediate hosts of F. gigantica, the conditions are thus favorable in Egypt to transmit fasciolosis which could also be caused by another fasciolid, F. hepatica, as the existance of this fluke was confirmed in Egypt.

Animals↗
PubMed2005

Impact of certain plants and synthetic molluscicides on some fresh water snails and fish.

The LC50 (78, 85 ppm) and LC90 (88, 135 ppm) of Anagalis arvensis and Calendula micrantha respectively against Biomphalaria alexandrina were higher than those of the non-target snails, Physa acuta, Planorbis planorbis, Helisoma duryi and Melanoides tuberculata. In contrast, the LC50 of Niclosamide (0.11 ppm) and Copper sulphate (CuSO4) (0.42 ppm) against B. alexandrina were lower than those of the non-target snails. The mortalities percentage among non-target snails ranged between 0.0 & 20% when sublethal concentrations of CuSO4 against B. alexandrina mixed with those of C. micrantha and between 0.0 & 40% when mixed with A. arvensis. Mortalities ranged between 0.0 & 50% when Niclosamide was mixed with each of A. arvensis and C. micrantha. A. arvensis induced 100% mortality on Oreochromis niloticus after 48 hrs exposure and after 24 hrs for Gambusia affinis. C. micrantha was non-toxic to the fish. The survival rate of O. niloticus and G. affinis after 48 hrs exposure to 0.11 ppm of Niclosamide were 83.3% & 100% respectively. These rates were 91.7% & 93.3% respectively when each of the two fish species was exposed to 0.42 ppm of CuSO4. Mixture of sub-lethal concentrations of A. arvensis against B. alexandrina and those of Niclosamide or CuSO4 at ratios 10:40 & 25:25 induced 66.6% mortalities on O. niloticus and 83.3% at 40:10. These mixtures caused 100% mortalities on G. affinis at all ratios. A. arvensis CuSO4 mixtures at 10:40 induced 83.3% & 40% mortalities on O. niloticus and G. affinis respectively and 100% mortalities on both fish species at ratios 25:25 & 40:10. A mixture of sub-lethal concentrations of C. micrantha against B. alexandrina and of Niclosamide or CuSO4 caused mortalities of O. niloticus between 0.0 & 33.3% and between 5% & 35% of G. affinis. The residue of Cu in O. niloticus were 4.69, 19.06 & 25.37 mg/1kgm fish after 24, 48 & 72 hrs exposure to LC0 of CuSO4 against B. alexandrina respectively.

Anagallis↗
PubMedDate not supplied

[Development of mother sporocysts of Echinostoma caproni (Trematoda: Echinostomatidae)].

New data on the migration and development of Echinostoma caproni mother sporocysts in two mollusk species of the genus Biomphalaria are obtained. It is confirmed, that the formation of primary and second generative cells takes place only as a result of undifferentiated cells' proliferation and following differentiation of some of them. These processes in miracidium, as well as in the parasitic stage of mother sporocyst, take place in a special organ, germinal mass, which occupies caudal position in both cases. The supposition of the role of germinal mass as the universal centre of multiplication and development of generative elements in all generations of Echinostoma caproni parthenites is confirmed. It is established, that mother sporocysts do not relize their reproductive potential completely, and the degree of its realization depends on the conditions arising in the host organism.

Animals↗
PubMed2006

Molluscicidal effect of three monoterpenes oils on schistosomiasis and fascioliasis vector snails in Egypt.

Thymol, Linalool and Eugenol showed considerable molluscicidal effect against Biomphalaria alexandrina, Bulinus truncatus and Lymnneae natalensis. The thymol was the potent one at least LC50 and LC90) followed by euganol then linalool. L. natalensis were more sensitive to these compounds followed by B. truncatus and then B. alexandrina. The LC50 & LC90) of thymol were 22 and 34 ppm against B. alexaldrina, 20 and 30 ppm for B. truncatuts and 18 and 29 ppm for L. nalalensis. These values were higher with Eugenol, 28 and 48 ppm for B. alexuadrina, 24 and 44 ppm for B. truncatus and 22 and 40 ppm for L. natalensis. Linalool showed highest values of LCs5 and LC90 against B. alexandrina, 34 and 56 ppm, against B. truncatus 30 and 52 ppm and for L. natalensis 28 and 48 ppm, respectively. Maintaining of B. alexandrina at LC10 of Thymol for one week induced an inhibitory effect in the level of some enzymes (AchE, SDH). It led to increase in the activity of other enzymes (ACP, ALP & G-6-PD). Acetylcholine-sterase activity (AchE) of treated B. alexandrina was significantly reduced by 45.9% when compared to control. The results showed a significant decrease in succinate dehydrogenase activity (SDH) by 46.4% together with a concomitant increase in glucose-6-phosphate dehydrogenase activity level (G-6-PD) by 47.5% in comparison with control. The activities of acid phosphatase and alkaline phosphatase enzymes were found to be higher in the treated snails than in control ones. The percentage increases were 47.2% & 73.2% respectively. The results also showed an elevation in the hemolymph glucose content of treated snails by 51.9% while the tissue glycogen content was reduced by 48.1%. The infection of B. alexandrina with S. mansoni miracidia was greatly reduced by thymol LC10 (sublethal dose). The infection rate reduction was 43.1%. The treated snails' prepatent period was prolonged (34.2 +/- 3.3 days) compared to control (28.4 +/- 1.2 days). A highly significant reduction of total cercarial production per snail occurred in experimental snails as compared to control.

Acyclic Monoterpenes↗
PubMed1991

Lectin-binding properties of the surfaces of in vitro-transformed Schistosoma mansoni and Echinostoma paraensei sporocysts.

As carbohydrates on the surfaces of sporocysts of digenetic trematodes may be targets of attack by the molluscan internal defense system, the lectin-binding patterns of living, in vitro-transformed sporocysts of Schistosoma mansoni and Echinostoma paraensei were characterized. Schistosoma mansoni sporocysts specifically bound 8 and E. paraensei 6 of 11 lectins examined. Sporocysts of the 2 species responded differently to 7 of the 11 lectins. Lectins inhibitable by mannose, galactose, and N-acetylgalactosamine were bound by both species. Lectins inhibited by fucose and N-acetylglucosamine bound uniquely to S. mansoni, and an N-acetylneuraminic acid (NeuNAc)-inhibitable lectin bound only to E. paraensei. Preincubation of sporocysts of either species in the plasma of the host snail Biomphalaria glabrata for as long as 24 hr only marginally altered the subsequent binding of lectins. Pretreatment of S. mansoni sporocysts with pronase E and trypsin substantially altered subsequent lectin binding, but similar treatment of E. paraensei sporocysts had little effect. A neuraminidase enzyme derived from Clostridium perfringens diminished binding of the NeuNAc-inhibitable lectin to E. paraensei sporocysts. This study indicates that lectin-binding monosaccharides are expressed abundantly on sporocyst surfaces, they vary considerably between 2 species parasitizing the same host, and they are not obscured readily or altered by exposure to host plasma.

Animals↗
PubMed1990

Intestinal schistosomiasis among children in a labour village of Wonji Sugar Estate, Ethiopia.

A survey for transmission of schistosomiasis was carried out in one of the labour villages of Wonji Sugar Estate, Ethiopia. Little or no schistosomiasis was present prior to establishment of this irrigation scheme. The survey revealed that 82% of the children between 5-14 years were now excreting S. mansoni eggs, and high intensities of egg excretion were observed (geometric mean intensity 377 eggs/g faeces, with 26% excreting greater than or equal to 1000 eggs/g). Large numbers of Biomphalaria pfeifferi snails were discovered in the irrigation canals near the village, of which 5% were shedding schistosome cercariae. No cases of urinary schistosomiasis were seen, although intermediate hosts of this infection were present. Poor maintenance of sanitary and water supply facilities, combined with a lack of community involvement in the control measures, were identified as major contributors to the dramatic rise in transmission. All children infected with S. mansoni were treated with praziquantel (40 mg/kg body weight). A follow up one month after chemotherapy indicated a cure rate of 69% and a reduction in geometric mean egg output of 77%.

Adolescent↗
PubMed1990

[Epidemiological study of schistosomes in a coastal lake of recent formation].

Parasitological and malacological surveys were conducted round a fresh water lake, previously a salted lagoon, in the South of Bénin and leaded to measure prevalence of schistosomiasis. 23 percent of population were found positive for Schistosoma haematobium and 13.4 percent for S. mansoni. Prevalences were different from locality to locality according to beach variations, but mean of parasite density was quite constant. Males were significantly more infected than females and young adults were more infected than children or old individuals. The prevalence distribution among people could be explained by behaviour and occupations. Five gastropod species were collected from which 2 are well known as intermediate host of S. haematobium (Bulinus globosus) and S. mansoni (Biomphalaria pfeifferi). A third species (Bulinus forskalii) which could be involved in S. haematobium transmission was found. Specimens of Bulinus were generally few and more represented in dry season. B. pfeifferi was more abundant especially at the end of rainy season. Populations of these 3 species were more dense by silty or swampy sides with shrub vegetation and poor oxygenated, acidic water rich in organic materials.

Adolescent↗
PubMed1989

Intestinal helminths in Akaki town, with special emphasis on the epidemiology of Schistosoma mansoni.

Two thousand, three hundred and nine stool specimens from about 5% of the residents of Akaki were examined by Kato thick smear technique for helminthic infections. The prevalence of various parasites was as follows: Schistosoma mansoni, 1.5%; Ascaris lumbricoides, 40.7%; Trichuris trichiura, 27.5%, Enterobius vermicularis, 2.2%; Taenia saginata, 3.2%; and Hymenolepis nana, 0.6%. Infected Biomphalaria pfeifferi snails were collected from the Fanta Stream, and 12% of the residents along the stream were infected with S. mansoni with an arithmetic mean of 437 eggs per gram of faeces (e.p.g.) as compared to 250 e.p.g. average town-wide, indicating that there was active transmission of S. mansoni. The prevalence of S. mansoni infection was low. It is suggested that it would be easier and more cost effective if control measures were applied at this stage.

Adolescent↗
PubMed1978

A simple quantitative technique for testing behavioral responses of Schistosoma mansoni miracidia to chemicals.

We describe a new technique for testing responses of Schistosoma mansoni miracidia to chemicals. Miracidia in spring water were placed in a chamber shaped like the Greek letter phi. Small volumes of test chemicals were inoculated into one side of the chamber. After 30 sec a dam was inserted to bisect the chamber and the percentage of miracidia on the inoculated side was calculated. Reproducible quantitative results were obtained using the known miracidial stimulants, snail-conditioned water (Biomphalaria glabrata) and Mg2+; up to 80% of the miracidia were recovered on the inoculated side of the chamber. Other substances also stimulated miracidia: several inorganic cations, 4 neurotransmitters, 3 acetycholine antagonists, and 1 acetycholine agonist. Modifying the technique by testing stimulants in altered chemical "backgrounds" allowed us to test for inhibitors of miracidial responses. Assays of the Mg2+ content of several of the test solutions indicated that their stimulatory or inhibitory effects could not be ascribed to Mg2+ contamination. However, results obtained with neurotransmitters and drugs were not sufficiently consistent to implicate specific neurotransmitters in the mechanism by which miracidia detect and respond to stimulants in snail-conditioned water.

Acetylcholine↗
PubMed1965

Molluscicidal properties and selective toxicity of surface-active agents.

Of over 100 commercially produced surface-active agents tested against the bilharziasis vector snail Biomphalaria sudanica, 13 were found to possess considerable and highly selective molluscicidal properties at concentrations of less than 1 ppm for exposures of 48 hours. Against crustacea, fish, water plants, mosquito larvae, mice, and the eggs of B. sudanica, the toxicities of the 13 surfactants were slight. The chemicals did not appear to be absorbed by organic matter to any appreciable extent. It is thought that the toxicity to B. sudanica is of both a chemical and a physical nature.

Animals↗