Miracidial attraction by Biomphalaria straminea, Lymnaea columella and Physa sp on miracidia of Schistosoma mansoni BH strain]

The attraction exercised over Schistosoma mansoni miracidia by Biomphalaria straminea, Lymnaea columella and Physa sp using a specially designed apparatus consisting of two circular glass chambers joined by an open channel were studied. The molluscs or their snail-conditioned water (SCW) was placed in one of the chambers (randomly chosen). In the channel ten miracidia was deposited and the count of miracidia in each of the three compartments (the two chambers and the channel) was recorded during fifteen minutes. Ten replications of each experiment with different specimens of molluscs and miracidia were made. Statistical and ad-hoc exploratory data analysis showed that: a) the three species of molluscs and their SCW attract the miracidia; b) Physa sp attract more miracidia then L. columella. There was an isolated single B. straminea specimen that had a repulsive effect to the miracidia.     

Schistosomiasis mansoni and distribution of freshwater mollusks in natural bodies of water in Niterói,Rio de Janeiro State,Brazil

The authors report on the distribution of freshwater mollusks in Niterói, Rio de Janeiro State, Brazil, and notification of schistosomiasis cases in this municipality from 1995 to 2000. All breeding sites favorable to freshwater mollusks were surveyed, showing the following species: Antillorbis nordestensis (Lucena, 1954), Biomphalaria straminea (Dunker, 1848), Biomphalaria tenagophila (Orbigny, 1835), Drepanotrema anatinum (Orbigny, 1835), Lymnaea columella Say, 1817, Melanoides tuberculatus (Müller, 1774), Physa cubensis Pfeiffer, 1839, Physa marmorata Guilding, 1828, and Pomacea sordida (Swainson, 1823). Some 3,691 specimens of snail hosts for Schistosoma mansoni Sambon, 1907 were examined by exposure to artificial light and crushing. No S. mansoni cercariae were found, although other types of cercariae were observed.     

Occurrence of schistosomiasis mansoni vectors on the Northern coast of the State of São Paulo, Brazil

This article comments on the detection of Biomphalaria tenagophila (d'Orbigny, 1835) infected with Schistosoma mansoni Sambon, 1907 in Caraguatatuba and the introduction of Biomphalaria straminea (Dunker, 1848) in Ilha Bela, two municipalities on the Northern coast of the State of S?o Paulo, Brazil. Infected snails were collected from a ditch located in the Olaria district. B. straminea and B. tenagophila were living in syntopy in a stream situated in Barra Velha. Such epidemiological findings indicate the risk of spread of schistosomiasis mansoni in the region, a consequence of inadequate basic sanitation.     

Long-term controlled field experiment on the competition between two species of Biomphalaria (Mollusca, Basommatophora), the snail vectors of Schistosoma mansoni in Northeastern Brazil

A long-term controlled field experiment on the interactions of the populations of Biomphalaria glabrata (target population) and B. straminea (competitor) was carried out in the county of Alhandra, state of Paraíba, Brazil, during the period 1980 through 1989. Results obtained in the current paper show that the snail B. straminea has strong competitive advantages over B. glabrata. In six out of nine streams the native population of B. glabrata were totally excluded and replaced by B. straminea. There is evidence showing that seasonal dryness has marked influence on the phenomenon studied in this paper. In all the streams were B. straminea already predominated, return of B. glabrata was never observed.     

The bioecology of snail vectors for schitosomiasis in Brazil

This paper describes the ecology of two species of Biomphalaria: B. glabrata and B. straminea. These species have been intensively studied in Brazil and in other countries since the 1950s. The literature in this area can be broadly subdivided into three categories, linked to three distinct historical periods: 1) an accumulated store of early studies carried out in the laboratory and in the field; 2) the development of quantitative ecological models; and 3) the development of an alternative methodology for breeding snails under seminatural conditions.     

The continued introduction of intermediate host snails of Schistosoma mansoni into Hong Kong

The South American planorbid snail Biomphalaria straminea, an intermediate host of Schistosoma mansoni, was first introduced into Hong Kong with tropical aquarium plants or fish around 1970. Genetic data indicate that a second introduction occurred in 1981-82.     

Relationship between the pathogenicity of Schistosoma mansoni in mice and the susceptibility of the vector mollusc. I. Cercariae infectivity and worm burden]

The possible influence of the immune mechanisms of the molluscs on the development of the sporocysts and the resultant behavior of the adult worm in the vertebrate host were studied. Two strains of Schistosoma mansoni (BH and SJ) were used. These were genetically selected for their susceptibility and maintained, respectively, in Biomphalaria glabrata and Biomphalaria tenagophila, the natural invertebrate hosts. Experimental groups of mice infected with cercariae proceeding from the two species of molluscs, belonging to generations P, F1, F2, F3 and F4, were formed. The infection rates of the snails, the number of the penetrant cercariae and the worm burden in mice were evaluated. It was concluded that the higher susceptibility of Biomphalaria tenagophila results in a greater ability on the part of the cercarial to develop into adult worms. The higher susceptibility of B. glabrata results in greater power of penetration into mice tegument on the part of the cercariae.     

First occurrence of Biomphalaria straminea in the South Goiano, Brazil

The objective of this note is to report the occurrence of the Biomphalaria straminea in the county of Cachoeira Dourada in the south of Goiás, and with that enhance the knowledge about its geographical distribution in the state. More than identify the species, the collection of thirty samples helped study and verify the presence of cercariae, especially because they were found in a setting which offers proper conditions to the development of a focal transmission site of schistosomiasis.     

Estivation of Biomphalaria tenagophila (Pulmonata, Planorbidae)

This study reports the finding of Biomphalaria tenagophila naturally aestived in two municipalities of the State of S.Paulo (Brazil): Ubatuba and Conchas. This ethological characteristic was discovered in 15 specimens collected in Ubatuba, and in 6 specimens collected in Conchas. The snails aestived showed vitality after being placed in water.     

Schistosomiasis: new occurrence of Biomphalaria straminea in Belo Horizonte, Minas Gerais

In Belo Horizonte, Minas Gerais, Brazil, the snail Biomphalaria straminea was found in the Pampulha region. Recently the snail was found in ditches in the old Santa Lúcia Reservoir, a now-extinct focus of schistosomiasis transmission by B. glabrata. The snails were collected and examined to verify whether they were naturally infected with Schistosoma mansoni. Negative specimens were used for breeding or infection with the LE strain of S. mansoni from the laboratory and another strain obtained from eggs found in the feces of a schoolchild (VGS) from Belo Horizonte. Among the 1890 snails collected from 1994 to 1995, none were infected with S. mansoni. Among 87 snails collected and exposed to the LE strain, 9 (10.3%) shed cercariae; among 83 snails from F1, and exposed to LE, 10 (12.0%) shed cercariae. Among 88 snails exposed to VGS, 10 (11.3%) shed cercariae. In Belo Horizonte, schistosomiasis is transmitted by B. glabrata and B. tenagophila. However, currently there exists the risk of appearance of a focus in which B. straminea could be the host if prophylactic measures are not taken by the authorities responsible for the construction of a park and lake at that site.     

Field tests on two new molluscicides (Molucid and WL 8008) in the Egypt-49 project area

In a continuing search for more effective molluscicides, tests were carried out in the Egypt-49 area on Molucid and WL 8008. Molucid, a 35% w/v solution of isobutyltriphenyl-methylamine (ICI 24223), was applied at 2 ppm for 6 hours; after the treatment, no live Bulinus truncatus, Biomphalaria alexandrina or Lymnaea caillaudi were observed for at least three months and snail densities remained low for at least seven months. Egg-masses were not affected by the treatment, however. WL 8008, N-tritylmorpholine, was applied as a 10% w/v emulsifiable concentrate in carbon tetrachloride (formulation 1), as a 20% w/v emulsifiable concentrate in tetrachlorethylene (formulation 2) or as bait. The two liquid formulations, applied at 0.25 ppm for 6 hours, gave a high initial kill, but snail densities regained their original levels within two months for Bulinus and within four months for Biomphalaria. The bait, applied at 62 lb—150 lb (28 kg—68 kg) per feddan, was ineffective. Like Molucid, WL 8008 is non-ovicidal.     

Distribution of Biomphalaria tenagophila and B. occidentalis in the State of S?o Paulo (Brazil)

The geographical distribution of Biomphalaria tenagophila (d'Orbigny, 1835) and B. occidentalis Paraense, 1981 in S. Paulo State, Brazil, is described. The first species being the most important intermediate host of Schistosoma mansoni Sambon, 1907. The second species is unsusceptible to transmission. The two species inhabit the limnic environments of great areas of S. Paulo, occasionally in simpatria. The 3,160 samples of mollusks collected between September 1981 and March 1986 were examined. B. tenagophila were identified in 1,062 of these samples from 203 municipalities and B. occidentalis in 255 samples from 97 municipalities. Biogeographical circumstances related to the distribution of the planorbids species are commented on.     

A malacological survey in city parks in Belo Horizonte, Minas Gerais, Brasil

The Greater Metropolitan Area of Belo Horizonte currently contains 18 city parks (also known as "ecological parks") with various bodies of water (lakes, springs, streams, etc). Initial research in 17 of these parks showed the occurrence of intermediate mollusk hosts for Schistosoma mansoni in at least 4. Monthly captures done from August 1994 to February 1996 showed the following results for these planorbids: Julien Rien Park: 1,145 specimens of Biomphalaria glabrata (2 to 13 mm); Betania Park: 149 specimens of B. glabrata (4 to 13 mm); Santa Lúcia Park: 2,431 specimens of B. straminea (3 to 9 mm); and Lagoa do Nado Park: 3 specimens of B. tenagophila (3 to 10 mm). Visits to the parks will continue, and after a diagnosis of each park's situation, control and/or eradication measures suitable for each one will be proposed to the municipal authorities.     

Discriminant analysis of free fatty acids of some Egyptian snails as a step for schistosomiasis control: new trends

Schistosomiasis is still the most common occupational health problem of rural workers in Egypt. The use of molluscicides, either chemical or biological, and environmental changing are the most successful methods of snail control. The new trend in Schistosoma control programs is to study the ecological factors that attract miracidium Schistosoma specific snails, to emphasizing to find out new environmental safe control methods. Since Schistosoma worms do not make fatty acids de novo, they require host lipids for survival and to complete their life cycle. Discriminate analysis of the estimated free fatty acids was done in this study in Biomphalaria alexandrina, Biomphalaria glabrata, and Bulinus truncatus, viz. Lymnaea truncatula and Physa acuta (Schistosoma intermediate and non-intermediate respectively). With the objective of determination of the biochemical difference that attract the infestation of Schistosoma miracidium to the target snails, as a step of the new control trends. Caprylic acid (C8:0), and Oleic acid (C18:1) are significantly lower in the tissues of Schistosoma intermediate snails compared to the non-intermediate snails. While, Capric acid (C10:0), Margaric acid (C17:0), and Lenoleic acid (C18:2) of the intermediate snails are significantly higher than that of non-intermediate snails. The percent of correct medical classification of snails are more than 80% according to Caprylic acid, Margaric acid, and Lenoleic acid, the other 15 fatty acids are less than 80%. These three free fatty acids could be chemoattractive of Schistosoma miracidium, and could be used as safe environmental control compounds, which needs further research.     

Trials with N-tritylmorpholine (Shell WL 8008) as a molluscicide in Southern Rhodesia

In the course of research into the effectiveness of new molluscicides for bilharziasis control, a recently developed compound, Shell WL 8008 (N-tritylmorpholine), has been tested in Southern Rhodesia, both in the laboratory and in the field. It is highly toxic to Bulinus (Physopsis) globosus, Biomphalaria pfeifferi and Lymnaea natalensis, all of which succumbed to the compound at a concentration of 1.0 ppm in a contact time of only 15 minutes. In experiments in reservoirs and natural watercourses, a concentrated aqueous suspension was sprayed on or just under the water surface, forming a white ”blanket” that sank at a rate depending on temperature, amount of vegetation, and so on. The period of contact with snails is sufficiently long for the molluscicide to kill them as it sinks; this characteristic is of great importance in the economic treatment of large stagnant water bodies or slow-moving streams. The compound is highly piscicidal, but has little effect on a wide range of microfauna.     

Attempts to Eradicate Snails from Impounded Water by the Use of N-Tritylmorpholine

This paper records attempts to overcome the problems of using a powerful but non-ovicidal molluscicide (N-tritylmorpholine) in eradicating snails from a dam by treating the water twice in 14 days. The first treatment was aimed at the existing snail population and the second at snails hatched from eggs that survived the first application. At each treatment an over-all concentration of 0.25 ppm was applied by spraying a 16% emulsifiable concentrate of N-tritylmorpholine from shore and boat to the water surface. The snails, Biomphalaria pfeifferi and Lymnaea natalensis, were first seen again 8 weeks from the start of the application in the region of 2 inlet furrows. When pretreatment levels of snails were again reached, a second double treatment was applied, again at an over-all concentration of 0.25 ppm but using a 50% paste formulation applied over 3 days for 3 hours per day to the inlet furrows. The snail kill was again 100% as measured by the sampling technique used but again young snails appeared 9 weeks later. The author concludes that single treatments at 5-week intervals probably represent the best means of control with N-tritylmorpholine.     

Development of molecular approaches for the identification of transmission sites of schistosomiasis

Primers targeting the gene encoding the small subunit rRNA were designed to amplify DNA from Schistosoma mansoni with high specificity. Three PCR systems were developed: conventional PCR, two-step nested PCR (NPCR) and single-tube nested PCR (STNPCR). The limits of detection of parasite DNA for the conventional PCR, NPCR and STNPCR were 10 pg, 0.1 fg and 1 fg, respectively. The assays were highly specific for S. mansoni and did not recognise DNA from closely related non-schistosome trematodes. Using pools of Biomphalaria molluscs, PCR, NPCR and STNPCR were positive in 6/16 (37.5%), 15/16 (93.8%) and 13/16 (81.3%) of the tested samples, respectively, whereas the observation of cercariae shedding after exposure to light was able to detect S. mansoni infection in 6/16 (37.5%) of the pools. Thus, the molecular detection systems had a higher level of sensitivity than standard screening of intermediate hosts by cercarial shedding when DNA was purified from pools of snails collected from endemic areas. These PCR protocols have potential to be used as tools for monitoring of schistosome transmission.     

Spatial analysis for stratification of priority malaria control areas, Mato Grosso State, Brazil

The goal of this study was to stratify priority areas for malaria control in the State of Mato Grosso, Brazil, based on spatial analysis. The variables used were: Annual Parasite Index (API), Plasmodium falciparum/Plasmodium vivax ratio, population variation, number of families settled, and percent of deforested area. The Moran's I and Local Moran Test were applied, visualized with the Box Map and Moran Map, for 1986- 1991, 1992-1997, and 1998-2003. Box Map identified areas with high, low, and intermediate priority for control, and Moran Map identified municipalities with significant autocorrelation. In the high priority area, located in the North of Mato Grosso, malaria incidence decreased drastically despite the increase in the number of municipalities from the first to the last period. Other municipalities were added to the lower priority area, from the Southeast, Southwest, and Central-South of the State. The intermediate priority area was located along the border with neighboring States and municipalities classified as high and low priority. Spatial analysis showed the importance of the neighboring phenomenon between municipalities in defining priority areas, thus highlighting the technique's advantages for use in malaria control and surveillance.     

Effects of locally targeted heavy-ion and laser microbeam on root hydrotropism in Arabidopsis thaliana

Classical studies on root hydrotropism have hypothesized the importance of columella cells as well as the de novo gene expression, such as auxin-inducible gene, at the elongation zone in hydrotropism; however, there has been no confirmation that columella cells or auxin-mediated signaling in the elongation zone are necessary for hydrotropism. We examined the role of root cap and elongation zone cells in root hydrotropism using heavy-ion and laser microbeam. Heavy-ion microbeam irradiation of the elongation zone, but not that of the columella cells, significantly and temporarily suppressed the development of hydrotropic curvature. However, laser ablation confirmed that columella cells are indispensable for hydrotropism. Systemic heavy-ion broad-beam irradiation suppressed de novo expression of INDOLE ACETIC ACID 5 gene, but not MIZU-KUSSEI1 gene. Our results indicate that both the root cap and elongation zone have indispensable and functionally distinct roles in root hydrotropism, and that de novo gene expression might be required for hydrotropism in the elongation zone, but not in columella cells.     

滑车上动脉蒂额部三叶瓣修复鼻尖鼻翼及鼻小柱缺损的疗效分析

目的：探讨应用滑车上动脉蒂额部三叶瓣同时修复鼻尖鼻翼及鼻小柱缺损的临床疗效及治疗经验。方法：选取2008年9月-2013年2月本院收治的5例同时存在鼻尖鼻翼及鼻小柱缺损的患者,均采用滑车上动脉蒂额部三叶瓣修复。手术分2期进行：Ⅰ期行皮肤扩张器置入额部帽状腱膜及额肌下扩张充足的皮肤软组织;Ⅱ期设计滑车上动脉额部三叶瓣转移修复鼻尖鼻翼及鼻小柱缺损。结果：本组5例滑车上动脉蒂额部三叶瓣全部存活,随访4-12个月,平均随访8个月,鼻外形、功能良好,皮瓣色泽、质地与周围皮肤基本一致。结论：滑车上动脉蒂额部三叶瓣能同时修复鼻尖鼻翼及鼻小柱缺损,修复后鼻外形、功能良好,疗效可靠,是治疗同时存在鼻尖鼻翼及鼻小柱缺损较理想的方法。