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PubMed2002

Toxicology of a potential molluscicide derived from the plant Solanum xanthocarpum: a preliminary study.

A potential molluscicidal extract, obtained from the indigenous Chinese plant Solanum xanthocarpum (Schrad. and Wendl), was tested for toxicity against snails and fish in static, acute-toxicity tests. The extract had a significant effect on mature and young snails of the amphibious Asian freshwater prosobranch Oncomelania hupensis (Gredler) and also on mature specimens of the freshwater pulmonate snails Biomphalaria glabrata (Say) and Lymnaea stagnalis (Linnaeus). The minimum dose that produced 100% mortality of snails exposed for 48h, 4.321mg/litre, is much less than the threshold, of 100mg/litre, set for a potential molluscicide by the World Health Organization. In contrast, the minimum concentration producing 100% mortality in the fish Gobiocypris rarus (Ye and Fu) was 17.28mg/litre. The extract also limited the extent of water-leaving by snails exposed to it, an important feature for the control of amphibious snails. This extract thus represents a promising plant-derived molluscicide which is worthy of further investigation.

Animals↗
PubMed2006

Schistosoma mansoni in infants (aged < 3 years) along the Ugandan shoreline of Lake Victoria.

In two complementary epidemiological surveys of villages on the Ugandan shoreline of Lake Victoria, the putative occurrence of intestinal schistosomiasis in the local infants (children aged < 3 years) was investigated. When, during the first survey, 136 mother-and-infant pairs from a total of 12 villages were studied, only 7% of the infants but 45% of the mothers were found to be egg-patent for Schistosoma mansoni infection. The use of dipstick tests for urine-circulating cathodic antigen indicated, however, a much higher prevalence, of approximately 40%, among the infants. In the second survey, urine samples and multiple, not single, stool samples were collected from another 19 mother-and-infant pairs in two of the 12 study villages (Bugoto and Bwondha), and a standardized questionnaire was implemented. The prevalence of egg-patent infection was then found to be markedly higher in the study infants from Bugoto (86%) than in those from Bwondha (25%). A greater level of mother-and-infant water contact, a higher abundance of (infected) Biomphalaria choanomphala, and an unusual lakeshore topology may explain why S. mansoni infection was so much more common in the Bugoto subjects than in the Bwondha. All but one of the infants studied in the second survey were found to be anaemic (with <110 g haemoglobin/litre). Taken together, these children were less likely to be found infected with hookworm (16%), Hymenolepis nana (11%) or Trichuris trichiura (5%) than with S. mansoni (47%). Infection with the parasites causing intestinal schistosomiasis can be common among the infants living in these lakeshore villages. Although the immediate and later-life clinical impacts of such infection have yet to be elucidated, such infants would probably benefit from regular de-worming. Mothers should be strongly encouraged to visit the nearest health-services clinic, with their infants, for any necessary anthelmintic treatment.

Animals↗
PubMedDate not supplied

Molluscicidal activity and new flavonoids from Egyptian Iris germanica L. (var. alba).

The molluscicidal activity of leaf and rhizome extracts of Iris germanica L. (var. alba) against Biomphalaria alexandrina snails was evaluated and the rhizome extracts were found to be the most potent. Activity-guided fractionation revealed that the chloroform extract showed the highest molluscicidal activity (LC90 = 1.26 mg/l) among the tested extracts of the rhizomes. Fraction B prepared from the chloroform extract was the most potent molluscicide (LC90 = 0.96 mg/l) in addition, it showed a significant heart rate reduction in the snail after a 6- to 24-h exposure period. It also displayed a significant level of cercaricidal potential in a time-concentration relationship pattern. Chromatographic fractionation and purification of fraction B resulted in the isolation of two novel compounds: 5,2'-dihydroxy-3-methoxy-6,7-methylenedioxyflavone and 5,7,2'-trihydroxy-6-methoxyflavanone. Their structures were established by one- and two-dimensional NMR methods and mass spectrometry.

Animals↗
PubMed1993

[Urban focus of schistosomiasis in a metropolitan area in a southeastern region of Brazil].

Urban focus of schistosomiasis in an urban area of South-eastern, Brazil. An active, urban focus of schistosomiasis in Belo Horizonte, MG, Brazil is described. It is located in the "Julien Rien" Park, a leisure area of 48,500 m2 created by the local administration in 1980 on the south side of city. Snail captures were made over 10 years (1983-1992) resulting in the collection of 3,361 Biomphalaria glabrata, ranging from 6.4 to 12.8 mm in diameter (mean = 9.3); 23 (0.7%) of these were found to be infected with Schistosoma mansoni. The finding of S. mansoni intermediate hosts in urban areas (ponds, small artificial lakes, etc) may be related to the introduction of fish and ornamental aquatic plants coming from specialized shops or areas in which they occur. It is suggested that the introduction of fish aquatic plants into urban water collections without a quarantine period should be avoided, as a prophylactic measure.

Animals↗
PubMed1995

[Relationship between the pathogenicity of Schistosoma mansoni in mice and the susceptibility of the vector mollusk. III. Mortality, body and viscera weight].

The relationship between the development of hepatomegaly, splenomegaly, body weight and mortality rate and the degree of susceptibility of Biomphalaria glabrata and B. tenagophila at which infective cercariae developed was studied. The study utilized Swiss mice, SPF, as definitive hosts and populations of snails genetically selected for character susceptibility as intermediate hosts. Low body weight and smaller viscera were observed in infected mice with cercariae originating from snails that showed a high degree of susceptibility. The higher susceptibility of molluscs infected with S. mansoni corresponded to a lower survival of the infected mice. These results lead to the conclusion that the higher degree of adaptation of the parasite to its intermediate hosts, evidenced by the high indexes of susceptibility, leads to different behaviour on the part of this parasite in its definitive host.

Analysis of Variance↗
PubMed2000

[Ecoepidemiology of urban schistosomiasis in Itamaracá Island, Pernambuco, Brazil].

INTRODUCTION: In 1988, 22 autochthonous cases from accidental exposure were registered in Forte Orange beach, Itamaracá Island, Pernambuco, Brazil. All cases occurred in middle-to-upper class individuals who were vacationing in the island. After the cases were identified, the major objective was to find breeding sites of schistosomiasis vectors and correlate the biological factors with the environmental conditions. METHODS: The environmental characteristics of the beach before human occupation were obtained from several documents. Also, a one-year malacological survey was conducted with monthly collection of mollusks, and the determination of their infectivity rates. RESULTS/CONCLUSIONS: The malacological survey was able to identify 20 breeding sites of Biomphalaria glabrata and 28 capture station were set up. Snails were collected and examined each month throughout a whole year. The results show a seasonal variation in the mollusk population density associated with infection rates and types of breeding sites. The importance of this new epidemiological profile of schistosomiasis in the State of Pernambuco relies on the fact that it can be related with the drastic human interference on the environment. Ecological, environmental, and demographic factors as well as the epidemiological characteristics of the disease have social and economic repercussions.

Animals↗
PubMedDate not supplied

Schistosomiasis mansoni in an area of low transmission. I. Impact of control measures.

This work was undertaken in the municipality of Pedro de Toledo (São Paulo State, Brazil) in 1987, to clarify aspects related to the transmission levels of Schistosoma mansoni in a human population where the snail host is Biomphalaria tenagophila. Since 1980 a control programme has been undertaken in this municipality. Urban and rural populations (4,719 subjects) were submitted to faecal examinations (Kato-Katz method). The overall prevalence rate was 4.8% being higher in males (6.2%) and also in the rural zone (5.8%). The geometric mean of S. mansoni eggs was 35.1 eggs per gramme of faeces (epg). Approximately 80.0% of the carriers presented less than 100 epg and only 20 individuals (9.0%) eliminated more than half of total eggs. The highest index of potential contamination (IPC) was in the age group of 5 to 20 years (57.6%). Two thirds of the investigated patients (207) were autochthonous of Pedro de Toledo. The geographical distribution of the carriers showed a clear aggregation of the autochthonous cases and a close association between human contact sites and breeding places of B. tenagophila. This study shows that schistosomiasis subjects were not randomly aggregated, the youngsters should be the main target in the prophylaxis, and the efficacy of the control programme.

Adolescent↗
PubMedDate not supplied

Evaluation of temporal, seasonal and geographic stability of the molluscicidal property of Euphorbia splendens latex.

Laboratory tests with aqueous solutions of Euphorbia splendens var. hislopii latex have demonstrated seasonal stability of the molluscacidal principle, with LD90 values of 1.14 ppm (spring), 1.02 ppm (fall), 1.09 ppm (winter), and 1.07 ppm (summer) that have been determined against Biomphalaria tenagophila in the field. Assays on latex collected in Belo Horizonte and Recife yielded LD90 values similar to those obtained with the reference substance collected in Rio de Janeiro (Ilha do Governador), demonstrating geographic stability of the molluscacidal effect. The molluscacidal action of aqueous dilutions of the latex in natura, centrifuged (precipitate) and lyophilized, was stable for up to 124 days at room temperature (in natura) and for up to 736 days in a common refrigerator at 10 to 12 degrees C (lyophilized product). A 5.0 ppm solution is 100% lethal for snails up to 13 days after preparation, the effect being gradually lost to almost total inactivity by the 30th day. This observation indicated that the active principle is instable. These properties together with the wide distribution of the plant, its resistance and adaptation to the tropical climate, its easy cultivation and the easy obtention of latex and preparation of the molluscicidal solution, make this a promising material for large-scale use in the control of schistosomiasis.

Animals↗
PubMedDate not supplied

[The susceptibility of Planorbidae from the metropolitan area of Belo Horizonte, MG (Brazil) to Angiostrongylus costaricensis (Nematoda, Angiostrongylidae)].

Biomphalaria glabrata (control), B. tenagophila and B. straminea from our laboratory colonies iniciated with molluscs collected in the municipality of Belo Horizonte, MG (Brasil), were experimentally infected with first-stage larvae of Angiostrongylus costaricensis. The number of molluscs of each species exposed was 139, 77 and 149. About 25 days later, surviving molluscs were individually examined by artificial digestion. Of 87 B. glabrata examined, 62 (71.3%) were positive and between one and 61 third-stage larvae were found; of 42 B. tenagophila, 21 (50.0%) contained between one five third-stage larvae; and of 89 B. straminea, 69 (77.5%) presented between one and 72 third-stage larvae. The three molluscan species are susceptible to A. costaricensis infection, but B. glabrata and B. straminea are most suitable for maintaining the nematode cycle in laboratory.

Angiostrongylus↗
PubMedDate not supplied

The prolonged use of niclosamide as a molluscicide for the control of Schistosoma mansoni.

Applications of niclosamide at three-monthly intervals were undertaken for 14 years in foci of Biomphalaria glabrata in the water sources of Peri-Peri (Capim Branco, MG). All the residents of the area were submitted to an annual fecal examination (Kato/Katz) and those individuals eliminating Schistosoma mansoni eggs were treated with oxamniquine. A malacological survey was undertaken at three-monthly intervals by means of ten scoops with a perforated ladle each ten metres along the two banks of the ditches and streams of the region. Where snails were found, molluscicide was applied by means of dripping or aspersion using a 3 ppm aqueous suspension of niclosamide. Initially, a mean of 14.3% of snails in the region were found to be eliminating cercariae. Following the first four applications of molluscicide, this was reduced to 0.0% and maintained at about 1.5% throughout the program. Thus, there was a continued possibility of schistosomiasis transmission in the area and it was observed that the population of snails reestablished itself within three months of molluscicide application. The results obtained in this study do not encourage the continual use of niclosamide as the only method of control of schistosomiasis.

Animals↗
PubMedDate not supplied

Schistosomiasis mansoni in an area of low transmission. II. Risk factors for infection.

Risk factors for Schistosoma mansoni infection were identified using a 1:1 matched case-control design. The work was conducted in the municipality of Pedro de Toledo, São Paulo State, Brazil, an area where the snail host is Biomphalaria tenagophila. Information on water contact patterns, knowledge, attitudes and practices (kap), socioeconomic and sanitary conditions were obtained by mean of questionnaires. The crude odds ratio estimates and the adjusted odds ratio estimates using the logistic regression model are presented. Most of the examined individuals admitted recent water contacts (90.6% of the cases). The most frequent reason for contact was swimming, playing and fishing and the preferential site of contact was the river. According to the logistic regression technique, the main risk factors for infection were: a) water contact through swimming, playing and fishing; b) fording; c) bad hygiene. We concluded that recreational activities are the main reasons for schistosomiasis transmission in Pedro de Toledo and leisure alternatives should be offered to the local population.

Animals↗
PubMedDate not supplied

[Preliminary trials of Guaiacum officinale L. as a molluscicide].

Aqueous suspensions of fruit's pericarp, leaves, root's bark and seeds of Guaiacum officinale were tested at different concentrations as molluscicide, cercaricide and piscicide. In the laboratory the suspension of fruit's pericarp produced 100% mortality for egg masses of B. glabrata at 100 ppm, for adult snails of Biomphalaria glabrata, B. straminea and B. tenagophila at 20 ppm, for Lebistes reticulatus (fishes) at 5 ppm and Schistosoma mansoni's cercariae at 1 ppm. The ethanolic extract of fruit's pericarp was not active against adult snails of B. glabrata. The lethal dose for adult snails(DL90) of the aqueous suspension of fruit's pericarp after 24 hours exposure, were: 15 ppm for B. glabrata; 14 ppm for B. straminea and 18 ppm for B. tenagophila. The DL90 of aqueous suspensions of root's bark, seeds and leaves were 57 ppm, 33 ppm and 15 ppm, respectively. In the field, B. glabrata adult snail mortality was 68% at 20 ppm and 100% at 40 ppm, when using suspension of fruit's pericarp.

Animals↗
PubMedDate not supplied

[Malacological survey of the Soledade lake hydrographic basin, in Ouro Branco (Minas Gerais, Brazil)].

A malacological survey was carried out at the Soledade Lake, in Ouro Branco, State of Minas Gerais, for the period 1986-1991. A total amount of 46,579 mollusks was collected, and among them seven species corresponding to five families could be found, as follows: 39,176 specimens of Biomphalaria tenagophila; 1,296 B. glabrata; 7 Drepanotrema cimex; 2,527 Physa sp; 417 Lymnaea sp; 92 Pomacea hastrum, and 3,064 specimens of Melanoides tuberculata (Melanniidae = Thiaridae) were collected from March/1990 onwards. Four specimens of B. tenagophila were found to be positive for Schistosoma mansoni.

Animals↗
PubMedDate not supplied

Genetic variation between susceptible and non-susceptible snails to Schistosoma infection using random amplified polymorphic DNA analysis (RAPDs).

Susceptibility of snails to infection by certain trematodes and their suitability as hosts for continued development has been a bewildering problem in host-parasite relationships. The present work emphasizes our interest in snail genetics to determine what genes or gene products are specifically responsible for susceptibility of snails to infection. High molecular weight DNA was extracted from both susceptible and non-susceptible snails within the same species Biomphalaria tenagophila. RAPD was undertaken to distinguish between the two types of snails. Random primers (10 mers) were used to amplify the extracted DNA by the polymerase chain reaction (PCR) followed by polyacrylamide gel electrophoresis (PAGE) and silver staining. The results suggest that RAPD represents an efficient means of genome comparison, since many molecular markers were detected as genetic variations between susceptible and non-susceptible snails.

Animals↗
PubMedDate not supplied

[Molluscacide and cercariacide activity of different species of Eucalyptus].

Hydrolates and essential oils of several Eucalyptus species were tested on adult snails and egg masses of Biomphalaria glabrata, and cercaria of Schistosoma mansoni. These products were obtained by vapor dragging. Eight out of 21 hydrolates presented activity on snails, nine on egg masses and three on cercaria at 1:4 dilutions. Eleven oils were active on both snails and egg masses at 20 ppm concentrations. The hydrolate of E. deanei was active both on snails, egg masses and cercaria at 1:4 dilution and its essential oil at 20 ppm.

Animals↗
PubMedDate not supplied

[Molluscacide activity of a mixture of 6-n-alkyl salicylic acids (anacardic acid) and 2 of its complexes with copper (II) and lead (II)].

The molluscicide activity of hexanic extract from Anacardium occidentale L. (cashew) nut shell, of copper (II) complex, of lead (II) complex and anacardic acid has been compared in the laboratory in an attempt to obtain better stability than anacardic acid. This was obtained from the hexanic extract of the cashew nut shell by precipitation with lead (II) hydroxide or cupric sulfate plus sodium hydroxide or (II) cupric hydroxide followed by treatment of lead (II) complex with a diluted solution of sulfuric acid. Ten products of the mixture obtained were tested on adults snails of Biomphalaria glabrata at 1 to 10 ppm. The most active products were copper (II) complex, obtained by cupric sulfate plus sodium hydroxide, and anacardic acid (sodium hydroxide) which presented activity at 4 ppm. The anacardic acid's lead content was above the limits accepted by the United States standards.

Animals↗
PubMedDate not supplied

[Identification of a new focus of schistosoma mansoni. (Municipality of Nova Lima, MG, Brazil].

The detection of a new transmission focus of schistosomiasis in Nova Lima town, Minas Gerais State, Brazil, is reported. The search of snail intermediate hosts in Banqueta do Bananal a small locality of Boa Vista neighbourhood detected 356 specimens of Biomphalaria glabrata, with a infection rate of 8.4%. In hundred-sixty-two patients stool examinations (Kato-Katz method) were done, showing ninety-one patients with eggs of Schistosoma mansoni in their feces. The integrated action of local residents and the local administration resulted in the elimination of the focus.

Adolescent↗
PubMedDate not supplied

[Geographic distribution of planorbidae in Santa Catarina, Brazil].

A revision of the malacological surveys carried out in Santa Catarina, Brazil, by the National Health Foundation in 52 counties of 8 microregions between 1981 and 1994 was made. Fifty of them were positive for Biomphalaria tenagophila, the only schistosome vector identified in the 94,535 specimens collected. Of 1,358 districts, 617 (45.4%) were positive to the vector, varying from 4.3% to 89.4% per municipality. The percentages of water bodies with planorbids varied from 0.2% to 26.3% and, of the total 28,120 examined 2,013 (7.1%) were positive. Snails infected with cercariae of Schistosoma mansoni were found in the counties of Araquari, Massaranduba, Joinville, Jaraguá do Sul and São Francisco do Sul, the last two constituting the southernmost focus of schistosomiasis mansoni in Brazil. Other planorbid species identified were B. peregrina, B. oligoza, B. schrammi, B. straminea and B. occidentalis.

Animals↗