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PubMed1997

[Control of intestinal schistosomiasis in Martinique island].

The presence of schistosomiasis mansoni is known in Martinique since the beginning of the XXth century. A general survey of the distribution of the disease was carried out in 1977 and showed a mean prevalence of 12% (coprology and serology taken together) in the whole of the island. Following this survey, an integrated control programme associating sanitary education, detection and treatment of patients and improved sanitation, was developed. In addition, a biological control programme against the intermediate snail host, Biomphalaria glabrata using the competitor snail, Melanoides tuberculata, was developed in the transmission sites. The decline of snail populations and of its parasite, as well as a strong reduction of the prevalence in humans were recorded between 1977 and 1996. At the present time, only few cases corresponding to older infections are detected. This epidemiological situation is quite different from that in Guadeloupe island where, in spite of an excellent control programme which was achieved on the Basse-Terre district, an important focus is still functioning on Grande-Terre district with the black rat as host reservoir. Such foci do not exist on Martinique island.

Animals↗
PubMed2001

Molluscicidal and trypanocidal activities of lapachol derivatives.

The activity of the potassium salt of lapachol against the snail Biomphalaria glabrata and its egg masses was tested. The obtained IC50 values (2.70 ppm and 1.43 ppm, respectively) are indicative of a strong activity. Lapachol derivatives were also assayed against infective trypomastigote blood forms of T. cruzi and the triacetoxy derivative of reduced lapachol showed relevant trypanocidal activity, killing 95.7% of the parasites at the concentration of 42 microg/mL.

Animals↗
PubMed1993

Schistosomiasis around Siavonga, on the shores of Lake Kariba, Zambia.

A schistosomiasis prevalence survey was carried out at Lake Kariba, Zambia--only the second since the creation of the lake more than 30 years ago. In the 20 or so years since the first study the prevalence of Schistosoma mansoni has increased from 16% to 56% while that of S. haematobium has dropped from 69% to 17%. There was variability in the infectivity of contact sites (P < 0.001) and this had an impact on prevalence. In contrast, sex, age (within the range 5-19 years), residential area (distance from the lakeshore) and activity at the contact site had no significant effect on prevalence (P > 0.05). The population at Matinangala was more at risk of infection by both S. haematobium (P < 0.001) and S. mansoni (P < 0.05) than the Siavonga population. Both Biomphalaria pfeifferi and Bulinus globosus were present in the area and factors which may be influencing their distribution are discussed.

Adolescent↗
PubMed1997

Laboratory assessment of the molluscicidal and cercaricidal activities of the Egyptian weed, Solanum nigrum L.

The molluscicidal properties of Solanum nigrum L. were tested against three Egyptian snail species (Biomphalaria alexandrina, Bulinus truncatus and Lymnaea natalensis), each an intermediate host of parasites causing human schistosomiasis or fascioliasis. The plant was collected in two regions within Egypt: Fayium and Giza. Snails were exposed for 24 and 48 h, to the dry powdered fruits and leaves or to crude water extracts of the powders, and mortality was recorded. The water extract of the leaves collected in Fayium (FLWE) had the highest molluscicidal activity, with median lethal concentrations (LC50) of 18.6 mg/litre for Bi. alexandrina, 14.5 mg/litre for Bu. truncatus and 17.7 mg/litre for L. natalensis. When Bi. alexandrina infected with Schistosoma mansoni were exposed to FLWE (20 or 25 mg/litre), they shed significantly fewer cercariae than unexposed snails (P < 0.02). The cercaricidal properties of FLWE were directly tested against S. haematobium, S. mansoni and Fasciola gigantica cercariae and a time-concentration relationship was observed; the concentrations needed to kill all cercariae (LC100) within 30 min of exposure were 30 mg/litre for both S. haematobium and S. mansoni and 40 mg/litre for F. gigantica.

Animals↗
PubMed2006

Acetogenins in Annona muricata L. (annonaceae) leaves are potent molluscicides.

An ethanolic extract of the leaves of Annona muricata was shown to be toxic to adult forms of the snail Biomphalaria glabrata (LC50 9.32 microg mL(-1)) and to larvae of the brine shrimp Artemia salina (LC50 0.49 microg mL(-1)). Activity-guided fractionation of the extract gave rise to a sample with high molluscicidal activity that contained the acetogenins, annonacin (90%), isoannonacin (6%) and goniothalamicin (4%).

Acetogenins↗
PubMed2002

Nitric oxide limits parasite development in vectors and in invertebrate intermediate hosts.

Nitric oxide (NO) possesses antiparasitic effects on both Protozoa and Metazoa in vertebrate definitive and intermediate hosts. Inducible NO limits parasite development also in Rhodnius prolixus and Anopheles stephensi, the natural vectors of human trypanosomiasis and malaria respectively, and in the snail Biomphalaria glabrata, a natural invertebrate intermediate host of human schistosomiasis. Therefore, NO limits Trypanosoma, Plasmodium, and Schistosoma development at all stages of the parasite life cycle.

Animals↗
PubMed1998

Ecology of larval mosquitoes, with special reference to Anopheles arabiensis (Diptera: Culcidae) in market-garden wells in urban Dakar, Senegal.

The urban area of Dakar, Senegal, contains > 5,000 market-garden wells that provide permanent sites for mosquito larvae, in particular Anopheles arabiensis Patton, the major vector of malaria. A study of the bioecology of mosquito larvae was conducted over 1 yr with a monthly visit to 48 of these wells. Overall, 9,589 larvae were collected of which 80.1% were Culicinae and 11.9% Anophelinae. Larvae from stages III and IV (n = 853) were identified to 10 species. An. arabiensis represented 86% of the anophelines collected and An. ziemanni Grunberg 14%. The most common Culicinae species included Aedeomyia africana Neveu-Lemaire, Culex quinquefasciatus Say, and Mimomyia splendens Theobald. Maximum anopheline abundance was observed at the end of the dry season in June, whereas maximum Culicinae abundance was observed at the end of the rainy season in September. Most wells (67%) did not harbor any An. arabiensis larvae and in the remaining 33% the larval abundance was low, averaging 0.54 larvae in stages III-IV per tray sample. To identify factors that determine the abundance of larvae in these wells, a co-inertia (multivariate) analysis was carried out to account for physicochemical variables (depth, turbidity, temperature, pH, conductivity, Na+, Cl-, HCO3-, CO3--, and NO3- concentrations) and biological variables (abundance of mosquito species, predators [e.g., fish, Dytiscidae, Notonectidae, odonates], molluscs [Bulinus and Biomphalaria], and surface plants [water lettuce, Lemna, and filamentous algae]). The co-inertia analysis indicated that the abundance of An. arabiensis was associated with Cx. quinquefasciatus and Cx. decens for the physiochemical data but was not associated with other mosquito species for floro-faunistic data. The conditions associated with abundant An. arabiensis were warm temperature (28-30 degrees C), clear and not too deep water (< 0.5 m), elevated concentrations of HCO3- and CO3--, low concentrations of NO3- and NaCl, low populations of larvivorous fish and invertebrate predators (notably odonates), the presence of water lettuce, and an absence of Lemna. These results indicate that many contributing factors influence the ecology of the immature stages of An. arabiensis.

Animals↗
PubMed2003

Parasite infection, host resistance and mate choice: battle of the genders in a simultaneous hermaphrodite.

Parasites have been proposed to be fundamental in the evolution of mate choice because differential mating on the basis of heritable disease resistance is expected to lead to progeny with a better genome-environment match than random mating. However, direct empirical data in support of this hypothesis are often lacking, and the relative influences of current and potential infection status (i.e. resistance genotype), and of mate choice versus mate conflict, remain largely unknown. We demonstrate experimentally, using simultaneous hermaphroditic snails (Biomphalaria glabrata) artificially selected for resistance or susceptibility to Schistosoma mansoni infection, that mate choice is influenced by a combination of current and potential parasitic infection status. As predicted by game-theory models, we also found a picture of conflict and cooperation: resistant and susceptible genotypes copulated in either gender and reciprocated (i.e. switched gender) equally when faced with an uninfected partner, but, by contrast, resistant snails actively refused to copulate as females with an infected partner. Such recognition and discrimination has implications for the maintenance of sex and the evolution of recognition systems.

Animals↗
PubMed2005

Origin and diversification of the human parasite Schistosoma mansoni.

Schistosoma mansoni is the most widespread of the human-infecting schistosomes, present in 54 countries, predominantly in Africa, but also in Madagascar, the Arabian Peninsula, and the Neotropics. Adult-stage parasites that infect humans are also occasionally recovered from baboons, rodents, and other mammals. Larval stages of the parasite are dependent upon certain species of freshwater snails in the genus Biomphalaria, which largely determine the parasite's geographical range. How S. mansoni genetic diversity is distributed geographically and among isolates using different hosts has never been examined with DNA sequence data. Here we describe the global phylogeography of S. mansoni using more than 2500 bp of mitochondrial DNA (mtDNA) from 143 parasites collected in 53 geographically widespread localities. Considerable within-species mtDNA diversity was found, with 85 unique haplotypes grouping into five distinct lineages. Geographical separation, and not host use, appears to be the most important factor in the diversification of the parasite. East African specimens showed a remarkable amount of variation, comprising three clades and basal members of a fourth, strongly suggesting an East African origin for the parasite 0.30-0.43 million years ago, a time frame that follows the arrival of its snail host. Less but still substantial variation was found in the rest of Africa. A recent colonization of the New World is supported by finding only seven closely related New World haplotypes which have West African affinities. All Brazilian isolates have nearly identical mtDNA haplotypes, suggesting a founder effect from the establishment and spread of the parasite in this large country.

Africa↗
PubMed1987

Anthelmintic properties of Polygonum glabrum.

A pure anthelmintic substance (PGA) has been isolated from the methanol-aqueous extract of the leaf of Polygonum glabrum Willd., a semi-aquatic Sudanese species of the family Polygonaceae. The antiparasitic in-vitro activity of several fractions isolated from the plant, has been examined comparatively with that of PGA. PGA also showed molluscicidal activity against Biomphalaria glabrata and Limnea truncatula Müll. Structural determination of PGA was attempted following data analysis of UV, IR, 13C NMR, 1H NMR and MS spectra and suggests that PGA is a terpenoid.

Animals↗
PubMed2003

Transmission of schistosomiasis in Kariba, Zimbabwe, and a cross-sectional comparison of schistosomiasis prevalences and intensities in the town with those in Siavonga in Zambia.

Given that the two communities lie only 10 km apart, on the northern shore of Lake Kariba, it is surprising that human schistosomiasis now appears to be a much less important health problem in Kariba town (Zimbabwe) than in Siavonga town (Zambia). In an attempt to explain this difference, the level and sites of Schistosoma haematobium and S. mansoni transmission in Kariba, and the prevalences and intensities of human infection with these parasites in both communities, have now been investigated. In a longitudinal study, a cohort of 378 schoolchildren, 150 subsistence fishermen and 42 commercial fishermen from Kariba town was screened three times for schistosome infection, at 6-month intervals. Sixteen human-water contact sites in or near the town were surveyed for intermediate host snails every month for 1 year. Finally, the results of screening 660 Kariba schoolchildren (in January 2001) and 527 Siavonga schoolchildren (in July 2002) were compared. In the longitudinal study, 9.0% of the schoolchildren, 7.3% of the subsistence fishermen and 0% of the commercial fishermen were each found positive for S. haematobium at least once. The corresponding values for S. mansoni were 2.5%, 12.5% and 26.3%, respectively. The results indicated that, each year in Kariba, 2.4% and 2.0% of schoolchildren and 18.2% and 5.2% of fishermen were infected with S. haematobium and S. mansoni, respectively. Although both Bulinus globosus and Biomphalaria pfeifferi were found at 14 of the 16 water-contact sites, snails infected with schistosomes that could infect mammals were only found at three of the sites. The problem of schistosomiasis in Kariba town appears to be greater among fishermen than schoolchildren, all transmission probably occurring in Lake Kariba. As expected, the overall prevalences of S. haematobium and S. mansoni infection among Siavonga schoolchildren (19.4% and 33.5%, respectively) were far higher than the corresponding values for Kariba schoolchildren (7.1% and 2.1%, respectively). The marked differences in the prevalence of human schistosomiasis between Kariba and Siavonga appear to be attributable to the better water and sanitation facilities and a history of schistosomiasis-control activities in Kariba town.

Adolescent↗
PubMedDate not supplied

A municipal level approach to the management of schistosomiasis control in Peri-Peri, MG, Brazil.

A schistosomiasis control program was implemented between 1974/87 in Peri-Peri, MG (622 inhabitants). Molluscicide (niclosamide) was applied at three monthly intervals in water sources with Biomphalaria glabrata, and individuals eliminating Schistosoma mansoni eggs in the feces were treated annually with oxamniquine. From 1974 to 1983 the control measures were undertaken by staff of the "René Rachou" Research Center FIOCRUZ (CPqRR), and from 1984 to 1987 these measures were included in the Capim Branco basic health network activities. During both periods, the prevalence, incidence, intensity of infection and hepatosplenic form as well as the number of infected snails decreased significantly. The prevalence decreased from 43.5 to 4.4%, the incidence from 19.0 to 2.9%, the overall intensity of S. mansoni from 281 to 87 and of the hepatosplenic form from 5.9 to 0.0%. The results obtained suggest that the municipal management of control measures was as effective as the vertical program conducted by CPqRR staff.

Adolescent↗
PubMedDate not supplied

Detection of IgM antibodies to Schistosoma mansoni gut-associated antigens for the study of the dynamics of schistosomiasis transmission in an endemic area with low worm burden.

For a period of 2 years, five follow-up measures of prevalence and incidence rates were estimated in a prospective study of S. mansoni infection in a group of schoolchildren who were living in a rural area of the Municipality of Itariri (São Paulo, Brazil), where schistosomiasis is transmitted by Biomphalaria tenagophila. Infection was determined by the examination of three Kato-Katz stool slides, and the parasitological findings were analyzed in comparison to serological data. In the five surveys, carried out at 6-month intervals (March-April and September-October), the prevalences were, respectively, 8.6, 6.8, 9.9, 5.8 and 17.2% by the Kato-Katz, and 56.5, 52.6, 60.8, 53.5 and 70.1% by the immunofluorescence test (IFT). Geometric mean egg counts were low: 57.8, 33.0, 35.6, 47.3 and 40.9 eggs per gram of feces, respectively. Of the total of 299 schoolchildren, who submitted five blood samples at 6-month intervals, one for each survey, 40% were IFT-positive throughout the study, and 22% were IFT-negative in all five surveys. Seroconversion from IFT negative to positive, indicating newly acquired S. mansoni infection, was observed more frequently in surveys carried out during March-April (after Summer holidays), than during September-October. Seasonal trends were not statistically significant for detection of S. mansoni eggs in stool. The results indicate that the use of IgM-IFT is superior to parasitological methods for detection of incidence of S. mansoni infection in areas with low worm burden.

Adolescent↗
PubMedDate not supplied

[Occurrence of snail vectors of schistosomiasis in a dam of the semi-arid region of Pernambuco State, Brazil].

The semi-arid region of Pernambuco state is not an endemic or focal area for schistosomiasis. The present work registers the occurrence of Biomphalaria straminea in a local dam with favorable chemical-physical characteristics to the proliferation of these mollusks. This observation gets the attention for the possibility of the introduction of the disease in this semi-arid region due to the growing multiplication of these dams.

Animals↗
PubMed1987

GP38, P28-I and P28-II: candidates for a vaccine against schistosomiasis.

Three antigens protective against Schistosoma mansoni have been extensively characterized. The schistosomulum surface antigen GP38 possesses an immunodominant carbohydrate epitope of which the structure has been defined. Protection can be achieved via the transfer of monoclonal antibodies recognizing the epitope or by immunization with anti-idiotype monoclonal antibodies. The glycan epitope is shared with the intermediate host, Biomphalaria glabrata as well as being present on other molluscs, including the Keyhole Limpet. A group of molecules at 28 kDa were initially characterized in adult worms and shown to protect rats and mice against a challenge infection. One of these molecules, P28-I, was cloned and expressed in E. coli, yeast and vaccinia virus. The recombinant antigen significantly protected rats, hamsters and baboons against a challenge infection. P28-I is a glutathione-S-transferase and the recombinant antigen produced in yeast exhibits the enzyme activity and has been purified to homogeneity by affinity chromatography. A second P28 antigen, P28-II, has also been cloned, fully sequenced and expressed. This recombinant antigen also protects against S. mansoni infection.

Animals↗
PubMedDate not supplied

[Natural infection of wild rodents by Schistosoma mansoni].

UNLABELLED: In Planalto, a small locality in the interior of the Bahia state, Brazil, 47% of sylvatic rodents were found to be naturally infected with Schistosoma mansoni, whereas the prevalence of the infection in the inhabitants of the area was 3.26%. The rodents (Nectomys) live near the houses, in contact with water, passing viable schistosome eggs in the stools. Worm burden is variable amongst such rodents. Periovular granulomas are small, especially in liver and intestines, and hepatic fibrosis is mild or absent, with no morphological evidence of portal hypertension being noted. Miracidia isolated from the eggs recovered from Nectomys readly infected laboratory-raised Bahia strain of Biomphalaria glabrata. Cercariae then obtained infected Swiss mice in a similar way as the human strains of S. mansoni kept in laboratory. Also, Swiss mice left in contact with water collections in Planalto were easily infected, which proved the transmissibility potential of the area. IN CONCLUSION: sylvatic rodents found in the area of Planalto tolerate well S. mansoni infection, eliminate viable eggs in the stools, are usually infected with a strain probably of human origin and therefore may play a role in maintaining parasite cycle in the area.

Animals↗
PubMedDate not supplied

Schistosomiasis in a low prevalence area: incomplete urbanization increasing risk of infection in Paracambi, RJ, Brazil.

The risk of schistosomiasis infection and heavy infection in the locality of Sabugo was evaluated in relation to housing in areas with different urbanization development and to residential supply with snail-infested water. Critical sanitary conditions were found in areas of incomplete urbanization, where healthy water supply sources were scarce, and draining of sewage, without previous treatment, was made directly to the water-bodies used for domestic and leisure activities, despite being Biomphalaria tenagophila snail breeding-places. Stool examinations (Kato-Katz and Lutz methods) showed prevalence of 2.9% mean intensity of 79 eggs per gram of stool and 47% of positive cases presenting intense infection. The use of snail-contaminated water for domestic purposes was considered a risk factor for infection. It is concluded that incomplete urbanization would facilitate transmission, probably enhancing the intensity of infection and that a low prevalence could hide a highly focal transmission. The relevance of these facts upon the efficiency of epidemiologic study methods and disease control planning are then discussed.

Animals↗
PubMed1998

Susceptibility of Nectomys rattus (Pelzen, 1883) to experimental infection with Schistosoma mansoni (Sambon, 1907): a potential reservoir in Brazil.

The aim of the present research was to evaluate the potential of Nectomys rattus, the "water rat", to develop Schistosoma mansoni infection. Comparison with N. squamipes was carried out. Both species of rodents were submitted to transcutaneous infection using different infective cercariae loads: 50, 100 or 500. N. rattus showed high susceptibility to S. mansoni, with an infection rate of 71%. Rodents were able to excrete viable eggs of S. mansoni in the faeces during all infection period. For both species, the small intestine, followed by the liver and the large intestine, presented the highest concentration of eggs among the surveyed organs. Infection caused no animal death. Moreover, N. rattus accomplished the parasite's life cycle, by infecting the snails Biomphalaria glabrata and later Mus musculus. These evidences indicate that both N. rattus, as for N. squamipes are potential reservoirs for schistosomiasis in Brazil. Considering the fact that N. rattus and N. squamipes exist in the same natural ecosystems of S. mansoni, we suggest that these rodents must be regarded as influential factors in epidemiology surveys.

Animals↗