Strain variation in the infectivity of Schistosoma mansoni for Biomphalaria glabrata

Five strains of Schistosoma mansoni resistant and susceptible to schistosomicides were studied for infectivity of 2 strains of Biomphalaria glabrata one of Puerto Rican origin and the other of Brazilian origin. Puerto Rican strains of S. Mansoni developed more slowly and had a lower infectivity in Brazilian B. glabrata than did the Brazilian S. mansoni. However, Brazilian S. Mansoni developed as well in Puerto Rican snails as in Brazilian snails, indicating that drug resistant strains could easily be moved by travel of infected persons from one area to another.

Repovoamento de criadouros de Biomphalaria glabrata após tratamento com niclosamida

Experimentos foram feitos no laboratório e no campo nos anos de 1980 a 1984, objetivando detectar as causas do repovoamento de criadouros de Biomphalaria glabrata após tratamento com niclosamida. Os bioensaios no laboratório mostraram que a suscetibilidade à niclosamida emulsionável de B. glabrata coletada mensalmente em um sistema de valas de irrigação, variou durante o ano. As concentrações letais CL90 foram 0,15 mgl-1 a 0,60 mgl-1, apresentando diferenças significantes estatisticamente (p < 0,01) nos meses de maio/82 e janeiro/83 e dezcmbro/82 e janciro/83, relacionadas a nutrição. No campo, foram tratados dois tipos de focos com solução aquosa a 10 ppm de niclosamida. O primeiro era formado por reservatório com cerca de 12.000 litros de água e continha 14,5% de moluscos infectados pelo Schistosoma mansoni. Uma única aplicação do produto, seguida de esvaziamento e limpeza do reservatório, eliminou os moluscos. O segundo, era constituído por sistema de valas e poço com 5,6% de moluscos infectados por S. mansoni. Uma única aplicação do produto, sem limpeza das valas, reduziu a densidade planorbídica 98%. As causas da sobrevivência de 2% dos moluscos do sistema de valas, são discutidas, sendo relacionadas ao substrato do criadouro e a técnica utilizada no tratamento.

First register of Biomphalaria straminea Dunker, 1848, in Santa Catarina State

The first register of Biomphalaria straminea, vector species of schistosomiasis, in Santa Catarina State, South Brazil is described. The specimens were obtained from two ornamental aquaria of private residences. In both cases the ornamental plants and/or fishes were bought from the same supplier. The presence of this species was later confirmed in the farm where these plants and fishes are cultivated, in the city of Governador Celso Ramos, also in Santa Catarina State. The occurrence in natural environments was later detected in two different places of the Island of Santa Catarina.

Immunoelectrophoretic study on common antigens of São Lourenço da Mata and Belo Horizonte strains of Schistosoma mansoni adult worms and Biomphalaria snails

Immunoelectrophoretic studies on common antigens were carried out by using rabbits sera immunized against São Lourenço da Mata and Belo Horizonte strains of Schistosoma mansoni adult worms and antigens of Biomphalaria glabrata pigmented (Jaboatão - PE); B. glabrata albino (Belo Horizonte - MG) and B. straminea (São Lourenço da Mata, PE). Furthermore, the reverse approach was proceeded, namely, sera anti Biomphalaria snails produced in rabbits were tested against both strains of Schistosoma adult worm antigens. The analysis of the common antigens between the SLM strains of S. mansoni adult worm and B. glabrata pigmented showed 8 to 9 precipitin bands, 3 bands with B. glabrata albino and only 1 band with B. straminea crude extracts. On the other hand, the BH strain of S. mansoni adult worm antisera produced 6 to 7 bands with B. glabrata pigmented, 5 bands with B. glabrata albino and 1 band with B. straminea antigenic extract. Biomphalaria snails crude extracts were fractionated by Sephadex G-100 column and three fractions were collected from each snail strain. The fractions were tested with anti SLM and BH strains of S. mansoni adult worm sera by immunoelectrophoresis. The common antigens fractionated from Biomphalaria snails crude extracts and those found for both strains of S. mansoni adult worm mostly existed in the first fraction and they were estimated to have molecular weight over 158,000 daltons. In our laboratory, it was found a relationship between the antigenic similarities and experimental infection rates of S. mansoni towards Biomphalaria snails so that more bands were seen with increasing infection rates of S. mansoni.

Suscetibilidade de planorbídeos da região metropolitana de Belo Horizonte, MG (Brasil) ao Angiostrongylus costaricensis (Nematoda, Angiostrongylidae

Lotes de Biomphalaria glabrata (controle), B. tenagophila e B. straminea (com respectivamente 139, 77 e 149 exemplares) criados em laboratório a partir de espécimes coletados na região metropolitana de Belo Horizonte, MG (Brasil), foram infectados experimentalmente com larvas L1 de Angiostrongylus costaricensis. Decorridos aproximadamente 25 dias, os moluscos foram digeridos individual e artificialmente para exame. De 87 B. glabrata examinadas, 62 (71,3%) estavam positivas e apresentaram de uma a 61 larvas L3; de 42 B. tenagophila, 21 (50,0%) possuíam de uma a cinco L3; e de 89 B. straminea, 69 (77,5%), de uma a 72 L3. As três espécies de planorbídeos mostraram-se suscetíveis à infecção pelo A. costaricensis, sendo a B. glabrata e a B. straminea as mais eficientes para manutenção do ciclo do nematódeo em laboratório.

O uso da casca da castanha do caju, Anacardium occidentale, como moluscicida alternativo

Bioensaios usando extratos hexânicos de cascas da castanha do caju, Anacardium occidentale, coletadas no Ceará em 1972 (amostra 1) e em 1987 (amostra 2) foram feitos sobre moluscos adultos e desovas de Biomphalaria glabrata, B. tenagophila e B. straminea, no laboratório e no campo. As cascas, 18,5 g, sem triturar amostra 1, também foram testadas sobre moluscos adultos e desovas das três espécies. A toxidez do extrato foi testada ainda sobre peixes (Poecilia reticulata) e girinos. As concentrações letais CL90, amostra 1, foram de 2,0 a 2,2 ppm para os moluscos das três espécies. Para B. glabrata adultos, recém-eclodidos e desovas as CL90, amostra 2, foram de 2,0, 0,5 e 30,0 ppm respectivamente. As cascas causaram mortalidade de 40 a 80% dos moluscos e de 22 a 35% dos embriões, ocasionando redução de 40 a 55% na oviposição das três espécies. O extrato hexânico, amostra 2, foi inócuo para girinos e peixes até 2 ppm. No campo, em poços com água parada, tratados com 20 ppm do extrato, amostra 1, ocorreu 97,1% de mortalidade de B. straminea e 100% de B. glabrata e B. tenagophila. Com a niclosamida a 3 ppm ocorreu 100% de mortalidade das três espécies.

Transmission of Schistosoma mansoni under experimental conditions using the bovine - Biomphalaria glabrata - bovine model

Three calves experimentally infected with Schistosoma mansoni, and passing viable eggs in feces, as well as 5 normal calves (coming from a non-endemic area for schistosomiasis) kept as controls, were maintained in an enclosure (850 m² in area). In this enclosure, a tank with water received 500 laboratory reared Biomphalaria glabrata. All the control calves were infected for a period ranging from 79 to 202 days after the beginning of the experiment, and afterwards presented viable S. mansoni eggs in feces. The mean worm recovery was 555. The snail population increased throughout the experimental period, showing a high number of B. glabrata infected with S. mansoni (42% on average). According to the present study, bovine has been suggested as having potentially a role in the maintenance of the life cycle of S. mansoni

Predation of Biomphalaria glabrata during the development of Belostoma anurum (Hemiptera, Belostomatidae)

Belostoma anurum was reared under laboratory conditions. Specimens were exposed to semi-natural conditions of photo period. The mortality rate was 26.3% during the post embryonic period (38.6 ± 0.7 days). During this time the average predation of Biomphalaria glabrata was of 99.0 ± 9.4 snails. The mean increment ratio of length and dry weight per instar was of 1.4 ± 0.1 and 2.8 ± 0.5, respectively. The predation by B. anurum adults can be divided into two different periods: phase I (4.8 ± 1.4 snails/day) and phase II (1.8 ± 0.5 snails/day). The higher predation in phase I suggested the sexual maturation of the belostomatid.

Ensaios preliminares do Guaiacum officinale L. como moluscicida

Suspensões aquosas do pericarpo do fruto, da casca da raiz, das folhas e das sementes de Guaiacum officinale foram testadas como moluscicida, cercaricida e piscicida em diferentes concentrações. Em laboratório, a suspensão do pericarpo do fruto apresentou 100% de mortalidade a 100 ppm para desovas de B. glabrata, a 20 ppm para caramujos adultos de Biomphalaria glabrata, B. straminea e B. tenagophila, a 5 ppm para Lebistes reticulatus (peixes) e a 1 ppm para cercárias de Schistosoma mansoni. O extrato etanólico do pericarpo do fruto não foi ativo para caramujo adulto de B. glabrata. As doses letais para 90% dos caramujos adultos (DL90), após 24 horas de exposição, usando a suspensão do pericarpo do fruto foram de: 15 ppm para B. glabrata; 14 ppm para B. straminea e 18 ppm para B. tenagophila. As DL90 das suspensões das casca da raiz, sementes e folhas contra B. glabrata foram de 57, 33 e 15 ppm, respectivamente. No campo, coma suspensão do pericarpo do fruto a mortalidade de caramujos adultos de B. glabrata foi de 68% a 20 ppm e 100% a 40 ppm

Production of Shistosoma mansoni cercariae by Biomphalaria glabrata from a focus in Belo Horizonte, Minas Gerais

The snail density, levels of infection and the monthly production of Schistosoma mansoni cercariae by Biomphalaria glabrata were determined in a focus of Barreiro de Baixo (Belo Horizonte, MG, Brazil). During a period of 38 months (1984 to 1987) 5,366 snails were collected of which 324 (6.03%) were infected with S. mansoni. The total number of cercariae shed was 5,667,312. Each snail shed an average of 17,422 cercariae during the time that it was under study in the laboratory. The greatest longevity of infected snails was 218 days. Natural cure was observed in 42 (12.9%) of the infected specimens about 130 days after collection. The average snail density in the focus during the period of study was 16.3 snails per scoop. The shedding of cercariae by snails collected from the field was compared with laboratory bred specimens infected in mass with the LE strain of S. mansoni from Belo Horizonte. The laboratory infected snails shed an average of 6,061 cercariae each, a value 2.8 times less than the field specimens due to a shorter life span. The prevalence of schistosomiasis in the focus was 14.3%.

Influence of temperature on development of Schistosoma mansoni female cercariae in Biomphalaria glabrata

In these experiments the ratio of male to female S. mansoni larvae in D. glabrata from Belo Horizonte and Ribeirão das Neves Minas Gerais, Brazil, either reared in laboratoty or collected in the field, varied from 1:1 to 1:1.3 or 1.4:1. Cercariae of LE strain of Schistosoma mansoni, shed by 39 snails maintained at 25±0.5ºC were used to infect mice on a weekly basis. Subsequent perfusion resulted in 76.6% male and 23.4% female worms. The cercariac produced by 32 infected snails maintained at 27+0.5°C were inoculated into mice and produced 43.4% male and 56.6% female worms (p<0.05). Cercariae eliminated by snails collected in Barreiro and Ressaca, Belo Horizonte, during hot months, produced 45.7 to 47.7% male and 52.3 to 54.3% female worms. A lower number of cercariae shed by snails collected in Gorduras, Belo Horizonte, at 20+3.0°C, produced 51.6% male and 48.4% female worms. Thus, in this region the infection of vertebrate hosts with S. mansoni cercariae would be more severe in the summer due to the higher level of parasites and the number of eggs.

Gamma 60Co DL50/30 of Biomphalaria glabrata (Say, 1818)

The variation of resistance to 60Co gamma-rays of Biomphalaria glabrata was studied. A population of 480 mollusks was observed during 30 days - distributed in 8 groups of snails isolated and 8 groups of snails in colonies - after exposure (30 snails per group per dose) to increasing doses of gamma radiation. Doses of 10, 20, 40, 60, 80, 160, 320 and 640 Gy from a Gamma-cell 60Co irradiator, were applied to the test groups and two groups control (non-irradiated) of snails - isolated and colony - were kept apart. After have been exposed, the snails were drew back to the aquaria where they were maintained before. The survival was estimated on a daily score of the alive animals in each group-dose, starting after the irradiation exposure day. As a result, the survival self-fertilization forms (DL50/30 = 218.2 Gy) was found greater than in cross-fecundation forms. These data point to a low radio-resistance on the cross-fertilization forms - the sexual reproductive form - which is most found in nature. The lower radio-resistance of the cross-fertilization forms suggests the presence of some sex-linked hormonal factor related to this phenomenon.

Comparative study of the fecundity and fertility of Biomphalaria glabrata (Say, 1818) and Biomphalaria straminea (Dunker, 1848) in a laboratory through self-fertilization and cross-fertilization

The aim of this study was to compare the fecundity and fertility of B. glabrata and B. straminea by cross- and self-fertilization. To attain this objective, laboratory-raised strains of B. glabrata and B. straminea were used. The former originated from natural breeding grounds in the municipality Paulista, state of Pernambuco, Brazil. The latter originated from irrigation ditches in the municipality of Petrolândia, in the same state. Snail populations of B. glabrata and B. straminea were maintained for 240 days in laboratory. Their fecundity was evaluated by noting the number of egg-masses, eggs and eggs per mass. Their fertility was evaluated by the number of viable eggs and the hatching rate. B. straminea was markedly more fecund than B. glabrata through cross- and self-fertilization, namely: greater egg-mass; higher egg production and more eggs per mass. Regarding fertility, there seemed to be no preferential period for occlusion to occur or a trend in the rhythm of producing viable eggs.

Aplicação da Técnica de "Nested PCR" Durante o Período Pré-patente para Identificação de Schistosoma mansoni no Hospedeiro Intermediário Biomphalaria glabrata

Biomphalaria glabrata, molusco de água doce, desempenha um importante papel em Parasitologia Médica, por ser o hospedeiro intermediário de Schistosoma mansoni, tremátode digenético responsável pela schistosomose intestinal. A detecção de moluscos infectados pelo Schistosoma mansoni tem uma grande importância em Saúde pública, porque identifica focos de transmissão da schistosomose. As limitações dos métodos clássicos para o diagnóstico de infecções pré patentes fazem com que os métodos de biologia moleculares sejam vistos como possíveis alternativas através da detecção de ADN do S. mansoni em moluscos hospedeiros. A detecção de sequências específicas de ADN por reacção de polimerase em cadeia (PCR) tem-se verificado ser de extrema importância para a análise genética e diagnóstico de várias doenças infecciosas. Neste estudo foi aplicada a técnica de Nested-PCR, com o objectivo de identificar, no período pré-patente, S. mansoni em moluscos expostos a 1, 5 e 10 miracídios em diferentes períodos de tempo. Foram utilizados moluscos das estirpes albina e selvagem de B. glabrata. Para a realização das técnicas de PCR e de Nested–PCR (NPCR) foram utilizados dois pares de oligonucleótidos desenhados especificamente para detectar o ADN de S. mansoni . Verificou-se amplificação do fragmento de ADN do parasita em 80% das amostras analisadas, independentemente da dose de miracídios e do período de exposição. O método utilizado é altamente sensível, mostrando ser uma ferramenta útil na detecção de hospedeiros intermediários de S. mansoni, consequentemente na identificação de focos de schistosomose intestinal. Palavras-chave: Schistosoma mansoni, Biomphalaria glabrata, período pré-patente e Reacção em Cadeia de Polimerase.

OVICIDAL EFFECT OF PIPERACEAE SPECIES ON Biomphalaria glabrata, Schistosoma mansoni HOST

SUMMARYSchistosomiasis is a neglected disease with public health importance in tropical and subtropical regions. An alternative to the disease control is the use of molluscicides to eliminate or reduce the intermediate host snail population causing a reduction of transmission in endemic regions. In this study nine extracts from eight Piperaceae species were evaluated against Biomphalaria glabrata embryos at blastula stage. The extracts were evaluated in concentrations ranging from 100 to 10 mg/L. Piper crassinervium and Piper tuberculatum extracts were the most active (100% of mortality at 20 mg/L and 30 mg/L respectively).