The adhesion of biofilm on dental prostheses is a prerequisite for the occurrence of oral diseases. Objective: To assess the antimicrobial activity and the mechanical properties of an acrylic resin embedded with nanostructured silver vanadate (β-AgVO3). Material and Methods: The minimum inhibitory concentration (MIC) of β-AgVO3 was studied in relation to the species Staphylococcus aureus ATCC 25923, Streptococcus mutans ATCC 25175, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231. The halo zone of inhibition method was performed in triplicate to determine the inhibitory effect of the modified self-curing acrylic resin Dencor Lay - Clássico®. The surface hardness and compressive strength were examined. The specimens were prepared according to the percentage of β-AgVO3 (0%-control, 0.5%, 1%, 2.5%, 5%, and 10%), with a sample size of 9x2 mm for surface hardness and antimicrobial activity tests, and 8x4 mm for the compression test. The values of the microbiologic analysis were compared and evaluated using the Kruskal-Wallis test (α=0.05); the mechanical analysis used the Shapiro-Wilk's tests, Levene's test, ANOVA (one-way), and Tukey's test (α=0.05). Results: The addition of 10% β-AgVO3 promoted antimicrobial activity against all strains. The antimicrobial effect was observed at a minimum concentration of 1% for P. aeruginosa, 2.5% for S. aureus, 5% for C. albicans, and 10% for S. mutans. Surface hardness and compressive strength increased significantly with the addition of 0.5% β-AgVO3 (p<0.05). Higher rates of the nanomaterial did not alter the mechanical properties of the resin in comparison with the control group (p>0.05). Conclusions: The incorporation of β-AgVO3 has the potential to promote antimicrobial activity in the acrylic resin. At reduced rates, it improves the mechanical properties, and, at higher rates, it does not promote changes in the control.

O programa de melhoramento genético de arroz do Instituto Agronômico visa a obtenção de cultivares de arroz altamente produtivas, características tecnológicas desejáveis e resistência a doenças. O presente estudo avaliou genótipos de arroz integrantes dos ensaios comparativos avançados quanto à qualidade sanitária e severidade de manchas nas sementes, peso das sementes por panícula e esterilidade das espiguetas. A qualidade sanitária das sementes variou conforme o sistema de cultivo, com alta incidência dos fungos Pyricularia grisea, Bipolaris oryzae e Microdochium oryzae no cultivo inundado, enquanto que sob irrigação por aspersão predominaram Pyricularia grisea, Phoma sorghina e Drechslera spp. A severidade de manchas nas sementes apresentou correlação negativa com peso da panícula e número de grãos cheios, e positiva com número de grãos chochos e porcentagem de esterilidade. Destacaram-se em condições de cultivo irrigado por inundação as linhagens IAC 1817 e IAC 1818, apresentando os menores índices de severidade de manchas, e também baixas porcentagens de esterilidade e altos pesos de grãos por panícula. Em terras altas sob irrigação por aspersão, destacaram-se a linhagem IAC 1776 e a cv. Bonança, com os menores índices de severidade de manchas, e a linhagem 1781, com baixas incidências dos mais importantes patógenos, e também baixa esterilidade. Esses resultados serviram como indicadores do nível de resistência e/ou tolerância dos genótipos a manchas de grãos.

Aiming the development of high yielding rice cultivars, IAC (Agronomic Institute of S. Paulo, Brazil) carries out a continuous breeding program focused on good-grain quality and disease resistance. Rice genotypes from the upland and irrigated advanced trials were evaluated for seed health, seed discoloration severity, panicle seed weight and spikelet sterility. The results showed that seed health varied according to the two environments. High seed incidence of Pyricularia grisea, Bipolaris oryzae and Microdochium oryzae occurred under irrigated conditions, whereas Pyricularia grisea, Phoma sorghina e Drechslera spp. in upland. Correlation coefficient values obtained were significant and negative for seed discoloration severity x panicle seed weight and filled grains, and positive for seed discoloration severity x empty spikelets and spikelet sterility. In lowlands, the lines IAC 1817 e IAC 1818 showed low values of seed discoloration severity, spikelet sterility and high seed weight per panicle. In upland, IAC 1776 line and cv. Bonança showed the lowest seed discoloration severity, while IAC 1781 line presented low incidences of the most important pathogens, and low spikelet sterility.

A técnica coproparasitológica de concentração em formol acetato de etila foi empregada para a quantificação de ovos de helmintos. O método quantitativo proposto foi padronizado utilizando-se o sistema comercial Coprotest® e amostras fecais contendo diferentes cargas de ovos de Ascaris lumbricoides. Para a comparação do Coprotest® quantitativo com outros métodos de quantificação de ovos, foi preparada em laboratório uma série de amostras fecais, com carga decrescente de ovos de A. lumbricoides, Trichuris trichiura e Schistosoma mansoni. Discutem-se as vantagens de se empregar um método capaz de detectar maior número de espécies de helmintos, além de protozoários, e que permita, concomitantemente, estimar a intensidade das infecções por geo-helmintos e S. mansoni nas populações. O Coprotest® quantitativo mostrou ser de aplicação viável, fornecendo resultados comparáveis a outros métodos quantitativos já descritos na literatura.

The formol ethyl acetate concentration technique was applied for the quantification of helminth eggs in fecal samples. The proposed quantitative method was standardized through the use of a commercial kit, Coprotest®, and fecal samples with different counts of Ascaris lumbricoides eggs. For the comparison of the quantitative Coprotest® with other methods of egg quantification, a series of fecal samples was prepared in laboratory, with decreasing number of A. lumbricoides, Trichuris trichiura and Schistosoma mansoni eggs. It is discussed the advantages of a method that is able of detecting different helminth and also protozoa species, allowing, in concomitance, to estimate in the populations the intensity of S. mansoni and geohelminth infections. The quantitative Coprotest® showed to be feasible, providing results that were comparable to the other quantitative methods already described in the literature.

Este estudo foi conduzido para avaliar o milho (Zea mays L.) AG 1051 e os sorgos (Sorghum bicolor, (L.) Moench) AG 2006 e BR 303, para produção de silagem, e verificar o efeito da substituição do farelo de soja por uréia (0, 50 e 100%), nas rações concentradas para bovinos confinados. As silagens foram usadas em dois experimentos e os animais foram distribuídos em delineamento experimental inteiramente casualizado. No primeiro, 72 bovinos mestiços F1 Pardo Suíço x Nelore, inteiros, com 20 meses de idade e 412 kg PV, foram distribuídos em arranjo fatorial 3 x 3 (silagem de milho e de sorgos e nível de substituição do farelo de soja por uréia). No segundo, 48 novilhos Nelore, com 34 meses e 378 kg PV, foram distribuídos em arranjo fatorial 2 x 3 (silagem de sorgos e nível de substituição do farelo de soja por uréia). Não houve diferença entre as forragens quanto às produções/ha de matéria seca total e de folha, colmo e à relação espiga/panícula. As plantas de milho e sorgo BR 303 apresentaram cerca de 53% de espiga/panícula quando comparado a 45% do sorgo AG 2006. Não houve interação entre as silagens e a fonte de nitrogênio. A silagem de milho propiciou melhor desempenho para os animais mestiços. Economicamente, o melhor resultado foi obtido com o uso da silagem de milho e do farelo de soja. O desempenho dos animais Nelores não foi influenciado pelo tipo de silagem e pela fonte de nitrogênio. Não houve diferença no retorno econômico para as silagens. Contudo, para as fontes de nitrogênio, o maior retorno economico foi obtido com o uso da uréia, seguido da mistura farelo de soja + uréia e, por último, com o farelo de soja.

This study was conducted to evaluate the corn (Zea mays L.) AG 1051 and the sorghums (Sorghum bicolor (L.) Moench) AG 2006 and BR 303, for silage production, and the effect of substitution of soybean meal by urea (0,50 and 100%) in the concentrated diets for feedlot cattle. The silages were used in two experiments and the animals were alloted to a completely experimental design. In the first, 72 F1 crossbred Brown Swiss x Nellore bulls, with 20 months of age and 412 kg LW were distributed to a 3x3 factorial arrangement (corn silage and sorghums silage and level of substitution of soybean meal by urea). In the second, 48 Nellore steers, with 34 month of age and 378 kg LW, were allotted to a 2 x 3 factorial arrangement (sorghum silage and level of substitution of soybean by urea). There were no differences between the forages as for production/ha of total dry matter and leaves, stem and of ear/panicle ratio. The corn and sorghum BR 303 plants presented about 53% of ear/panicle ratio as compared to 45% of the sorghum AG 2006. There was no interaction between the silage and the nitrogen source. The corn silage provided better performance for the crossbred bulls. Economically, the highest profit was obtained by using corn silage and soybean meal. The performance of Nellore steers was not affected by silage type or nitrogen source. There were no differences in the economic return for the silages. However, for the nitrogen source, the higher economic return was obtained by the use of urea followed by soybean meal + urea mixture and, finally, by soybean meal.

Dados de prevalência e incidência da esquistossomose foram estimados, acompanhando-se um grupo de escolares residentes em área rural do município de Itariri (São Paulo, Brasil), por um período de 2 anos, com cinco inquéritos, um a cada semestre, realizados no primeiro semestre de cada ano entre março e abril e no segundo, entre setembro e outubro. O hospedeiro intermediário do Schistosoma mansoni na área é a Biomphalaria tenagophila. A infecção pelo S. mansoni foi determinada pelo método parasitológico de Kato-Katz, através do exame de três lâminas, e os resultados analisados comparativamente aos da reação de imunofluorescência para detecção de anticorpos IgM (RIF-IgM). Foram encontrados nos cinco inquéritos índices de prevalência de 8,6%, 6,8%, 9,9%, 5,8% e 17,2% pelo método parasitológico, e de 56,5%, 52,6%, 60,8%, 53,5% e 70,1%, pelo sorológico. As médias geométricas do número de ovos por grama de fezes (opg) foram baixas: 57,8, 33,0, 35,6, 47,3 e 40,9 opg, respectivamente do 1º ao 5º inquérito. Dos 299 escolares que se submeteram à RIF-IgM nos cinco inquéritos, 40% apresentaram-se positivos e 22% negativos no decorrer do acompanhamento. Soroconversão de negativo para positivo pela RIF-IgM, indicando provável infecção recente, foi observado com maior frequência nos inquéritos realizados no primeiro semestre (pós-verão), que no segundo semestre. A pesquisa de ovos nas fezes não mostrou sensibilidade para detectar essa sasonalidade. Os resultados indicam a superioridade da RIF-IgM para determinação de incidência de S. mansoni em áreas de baixa endemicidade.

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.

The detection of IgM antibodies for Schistosoma mansoni using gut-associated antigens (IgM-IFT) was compared to the parasitological Kato-Katz method for study of the transmission of schistosomiasis in an urban area in Campinas. About 400 schoolchildren whose ages ranged from 6 to 18 years, were observed for a period of two years. Blood samples on filter paper and fecal samples were collected, at intervals of six months. Serological (IgM-IFT) prevalence rates of 1.2%, 4.3%, 3.6%, 2.9% and 3.4% were obtained in five surveys carried out. S. mansoni eggs were detected in only one child out of the 225 children (0.4%) who were submitted to the Kato-Katz method (three slides for each fecal sample) in the 1st survey. Sixty eight children who submitted five blood samples, one for each survey, were found IFT negative throughout the study. No child was found to be IFT positive in all five surveys, and only four children showed IFT positive results in at least four surveys. Seroconversion from IFT negative to positive was observed from the 1st to the 2nd survey in six chidren, from the 2nd to the 3rd survey in three children, from the 3rd to the 4th survey in four children, and from the 4th to the 5th survey in two cases. However, confirmation of S. mansoni infection using the fecal examination was not possible in any of the cases. Also, in most of them the IFT result oscillated from negative to positive and vice versa. Our data implied that recent transmission of schistosomiasis in the study area was not possible.

The potential of an immunofluorescence test for detection of IgM antibodies against Schistosoma mansoni gut-associated antigens (IgM-IFT) was evaluated as a tool for studying aspects related to the schistosomiasis transmission in Ribeirão Pires, in the metropolitan area of the capital of the State of São Paulo, Brazil. Children from a school with about 400 students, 6 to 18 years, were followed-up for two years. In the five surveys, carried out at 6-month intervals, from October 92 to October 94, serological (IgM-IFT) prevalence indices of 5.3%, 5.8%, 6.2%, 2.9% and 3.3% were obtained. These indices were 7 to 10 times higher than the parasitological prevalence indices of 0.5%, 0.5%, 0.7%, 0.4% and 0% determined by the Kato-Katz method. Seroconversion from IFT negative to positive was indicating possible newly acquired S. mansoni infection in three children. But confirmation of infection by fecal examination was possible in only one child. The IgM-IFT can constitute a valuable tool for the improvement of the vigilance program in low endemic areas for schistosomiasis, better characterizing the S. mansoni transmission in such areas.

The susceptibility of four isolates of Schistosoma mansoni (BH, MAP, MPR-1 and K) to four multiple doses of anti-schistosomal agents (hycanthone, niridazole, oxamniquire, and praziquantel) were evaluated in infected female Swiss albino mice. These schistosomal isolates had been maintained in the laboratory without further drug pressure for 20 to 30 generations. Multiple dosage regimens were used for each drug against each isolate of S. mansoni to generate ED50 (effective dose 50%) values. Results demonstrated that the K isolate is resistant to niridazole, the MPR-1 isolate to oxamniquine, and the MAP isolate to both hycanthone and oxamniquine. The BH isolate was susceptible to all drugs and was used as the reference isolate. All isolates were susceptible to praziquantel. The significance of the difference in response of the MPR-1 and MAP isolates is discussed. These results confirm the resistance of these isolates of S. mansoni of three schistosomicides and demonstrate that the resistance of these isolates are stable over long periods of time without exposure to drugs.

Dentre as regiões do Estado de São Paulo, onde Biomphalaria tenagophila é hospedeira intermediária, o vale do Ribeira é área endêmica da esquistossomose. Nos últimos onze anos a endemia vem sendo intensamente controlada no vale, principalmente, nos municípios de Pedro de Toledo e Itariri. Estudamos a suscetibilidade de B. tenagophila de Itariri à linhagem simpátrica de Schistosoma mansoni, isolada do campo em 1988 e mantida no laboratório em camundongos suiço e B. tenagophila. Estudou-se a 2ª geração do trematódeo. Constituiram-se 3 grupos de 60 moluscos cada, sendo um grupo exposto a um miracídio e outro a 10 e um grupo controle não infectado. Observou-se mortalidade e eliminação de cercárias durante 78 dias. Findo este período, foram seguidos apenas moluscos que liberaram larvas até cessar sua eliminação. Nos moluscos expostos a 1 e 10 miracídios as mortalidades foram de 23% e 31% e os índices de infecção de 8% e 60% respectivamente, assim como a eliminação de cercárias foi de 82 e 104 dias. No controle a mortalidade foi de 22%. Assim, podemos concluir que B. tenagophila apresenta boa adaptação a linhagem simpátrica de S. mansoni

In the São Paulo State, Brazil, where the Biomphalaria tenagophila is the intermediate host, the Ribeira Valley is an important endemic schistosomiasis mansoni area. During last eleven years there has been intense control measures focusing on schistosomiasis. The efforts have been concentrated in the municipalities of Pedro de Toledo and Itariri. We determined the susceptibility of B. tenagophila to sympatric strain of S. mansoni, both recently isolated from Itariri field. In 1988, this strain was isolated and maintained in the experimental model: Swiss mice - sympatric B. tenagophila. The second generation of the worm was evaluated. The snail were divided in the three groups of 60 snails each. One group was exposed to 1 miracidium and other to 10. The third group was the control. The mortality and the shedding of cercariae were checked during 78 days. After that, the positive snails were observed until they ceased to shed cercariae. The exposed molluscs showed mortality rates of 23% and 31% and infection indexes were of 8% and 60% to 1 and 10 miracidia respectively. The mortality was of 22% in the control group. The periods of shedding cercariae in the two groups were 82 and 104 days. We can conclude that B. tenagophila is an effective intermediate host to the sympatric strain of S. mansoni sympatric strain

Este trabalho foi realizado no município de Pedro de Toledo, no Estado de São Paulo, Brasil, em 1987 para esclarecer aspectos sobre níveis de transmissão ao homem de Schistosoma mansoni, quando o hospedeiro intermediário é Biomphalaria tenagophila. Desde 1980 vem sendo desenvolvido um programa de controle neste município. Foram submetidos a exames de fezes (método de Kato-Katz) 4.719 indivíduos das zonas rural e urbana. A taxa de prevalência foi de 4,8%, sendo maior nos homens (6,2%) e também na zona rural (5,8%). Foi de 35,1% a média de ovos de S. mansoni por grama de fezes (epg). Cerca de 80,0% dos portadores apresentavam menos de 100 epg e somente 20 indivíduos (9,0%) eliminavam mais do que metade do total de ovos. Os mais altos índices de potencial de contaminação (IPC) ocorreram nos grupos etários de 5 a 20 anos (57,6%). Dois terços dos pacientes investigados (207) eram autóctones de Pedro de Toledo. A distribuição geográfica dos portadores demonstrou evidente agregação dos casos autóctones, assim como uma íntima associação entre locais de contato da população com os criadouros de B. tenagophila. Este estudo demonstra que os portadores de S. mansoni não estão agregados ao acaso, que os jovens devem ser o principal objetivo na profilaxia, e que o programa de controle foi eficaz.

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 potencial 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.

Desde 1980, está-se estudando a epidemiologia e o controle da esquistossomose mansônica no Município de Pedro de Toledo (Estado de São Paulo, Brasil). Em 1980 a prevalência avaliada por exame de fezes (método de Kato-Katz) foi de 22,8%. Estatisticamente, ao nível de 5%, não houve diferença nas prêvalencias observadas nas zonas rural e urbana. A intensidade de infecção foi baixa (média geométrica de 58,5 ovos por grama de fezes). As maiores prevalências e intensidades de infecção foram registradas na faixa etária de 5 a 29 anos. Geralmente a transmissão da endemia verificou-se durante o lazer. Apenas 0,4% de B. tenagophila mostraram-se positivos para cercárias de S. mansoni. A maioria dos portadores era assintomático. O programa de controle foi intensificado após avaliação dos dados de 1980, resultando em diminuição acentuada da prevalência de 22,8% em 1980 para 6%. Esta prevalência residual vem se mantendo até 1987. Agora iniciamos estudos para investigar as possíveis causas dessa prevalência residual.

The epidemiology and control of schistosomiasis mansoni in the Municipality of Pedro de Toledo (State of S. Paulo, Brazil) since 1980, has been studied. In 1980 the prevalence evaluated by stool exams (Kato-Katz method) was 22.8% and no statistical difference at 5.0% level was observed between rural and urban zones. The intensity of infection was low (58.5 eggs/g of faeces); the highest prevalence and intensity of infection rates were observed within the group of from 5 to 29 years of age, respectively. The transmission of schistosomiasis usually occurred during leisure time. The majority of the carriers of the parasite were asymptomatic. Of the B. tenagophila examined only 0.4% were found to be infected. The control programme has been intensified from 1981 on resulting in a sharp decrease in the prevalence from 22.8% in 1980 to 6% at the present time. This result shows that, in spite of the control programme there is a residual human prevalence. A beginning has been made on the investigation into the possible causes of this residual prevalence (6.0% was maintained through out 1987).

Desde 1980, está-se estudando a epidemiologia e o controle da esquistossomose mansônica no Município de Pedro de Toledo (Estado de São Paulo, Brasil). Em 1980 a prevalência avaliada por exame de fezes (método de Kato-Katz) foi de 22,8%. Estatisticamente, ao nível de 5%, não houve diferença nas prêvalencias observadas nas zonas rural e urbana. A intensidade de infecção foi baixa (média geométrica de 58,5 ovos por grama de fezes). As maiores prevalências e intensidades de infecção foram registradas na faixa etária de 5 a 29 anos. Geralmente a transmissão da endemia verificou-se durante o lazer. Apenas 0,4% de B. tenagophila mostraram-se positivos para cercárias de S. mansoni. A maioria dos portadores era assintomático. O programa de controle foi intensificado após avaliação dos dados de 1980, resultando em diminuição acentuada da prevalência de 22,8% em 1980 para 6%. Esta prevalência residual vem se mantendo até 1987. Agora iniciamos estudos para investigar as possíveis causas dessa prevalência residual.

The epidemiology and control of schistosomiasis mansoni in the Municipality of Pedro de Toledo (State of S. Paulo, Brazil) since 1980, has been studied. In 1980 the prevalence evaluated by stool exams (Kato-Katz method) was 22.8% and no statistical difference at 5.0% level was observed between rural and urban zones. The intensity of infection was low (58.5 eggs/g of faeces); the highest prevalence and intensity of infection rates were observed within the group of from 5 to 29 years of age, respectively. The transmission of schistosomiasis usually occurred during leisure time. The majority of the carriers of the parasite were asymptomatic. Of the B. tenagophila examined only 0.4% were found to be infected. The control programme has been intensified from 1981 on resulting in a sharp decrease in the prevalence from 22.8% in 1980 to 6% at the present time. This result shows that, in spite of the control programme there is a residual human prevalence. A beginning has been made on the investigation into the possible causes of this residual prevalence (6.0% was maintained through out 1987).

Com duas linhagens de Biomphalaria glabrata foi estudada a suscetibilidade de cinco cepas de Schistosoma mansoni resistentes e suscetíveis a esquistossomicidas. Três cepas do trematódeo oriundas de Porto Rico apresentaram desenvolvimento mais lento e menor índice de infecção em B. glabrata brasileira quando comparados com o comportamento de duas cepas de S. Mansoni provenientes do Brasil. Por outro lado, as cepas brasileiras do parasita desenvolve ram bem e infectaram mais de 90% dos exemplares de B. glabrata portorriquenhos. Entre os resultados, ressalta-se que cepas resistentes a esquistossomicidas poderão ser introduzidas por pacientes em diferentes áreas geográficas como Brasil e Porto Rico.

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.

Em condições experimentais foi estudada a suscetibilidade de Biomphalaria glabrata, B. straminea e B. tenagophila a quatro linhagens humanas (MAP, PTH, UPH, e OuH) e duas de roedores silvestres (PTR e VPR) do Schistosoma mansoni. Grupos de 50 moluscos foram expostos individualmente a 10 miracídios e observados durante 70 dias. Avaliou-se a suscetibilidade dos moluscos ao parasito por meio da % de animais com esporocistos, % de moluscos que eliminavam cercárias e mortalidade conjunta dos animais expostos e infectados. Exemplares de B. glabrata mineira infectaram-se com cepa simpátrica (MAP) e com 5 alopátricas do Estado de São Paulo (PTH, VPH, OuH, PTR e VPR). B. glabrata paulista mostrou altas taxas de infecção com as cepas MAP, VPR e OuH do trematódeo. Quatro % dos exemplares B. straminea de São Paulo eliminavam cercárias de cepas simpátricas; com cepa mineira apenas 4% apresentaram esporocistos na vigência de 20 miracídios por molusco; as menores taxas de mortalidade foram registradas com essa espécie de molusco, não sendo maior do que 20%. B. tenagophila paulista foi suscetível apenas às linhagens simpáticas sendo 6% a maior taxa de moluscos que eliminaram cercárias. Os resultados indicam que os movimentos populacionais humanos dentro do território paulista e para fora dele são importantes na disseminação da esquistossomose mansônica.

The susceptibility of 3 species of snails from, Brazil, B. glabrata (Minas Gerais - MG - and São Paulo - SP - States), B. tenagophila (SP) and B. straminea (SP) to experimental infection with 4 human (MAP, PTH VPH, and OuH) and 2 rodent (PTR and VPR both from SP) isolates of S. mansoni was studied. Snails of each species were exposed individually to 10 miracidia and observed during a 70 day experimental period for mortality, sporocyst development and number of snails shedding cercariae. The B. glabrata from MG -was found to be susceptible to MAP (MG) and 5 from SP (PTH, VPH, OuH, PTR and VPR). The B. glabrata from SP -was found to be susceptible to MAP, OuH and VPR. High mortalites were observed among B. glabrata from SP. The B. stramlnea was found to be susceptible to MAP (only sporocysts), OuH and VPR parasites; mortality rates were lower in this species of snail than in the other species tested. B. tenagophila from SP was found to be susceptible only to sympatric strains, but with low infection rates. The results indicate the importance of transmission of schistosome by human migration from São Paulo to other Brazilian areas.

Drug resistance associated with the treatment of human schistosomiasis appears to be an emerging problem requiring more attention from the scientific community than the subject currently receives. Drug-resistant strains of Schistosoma mansoni have been isolated by various investigators as a result of laboratory experimentation or from a combination of field and laboratory studies. Review of this data appears to indicate that the lack of susceptibility observed for some of the isolated strains cannot be ascribed solely to previous administration of antischistosome drugs and thus further studies are required to elucidate this phenomena. Strains of S. mansoni have now been identified from Brazil which are resistant to oxamniquine, hycanthone and niridazole; from Puerto Rico which are resistant to hycanthone and oxamniquine; and from Kenya which are resistant to niridazole and probably oxamniquine. Strains derived by in vitro selection and resistant to oxamniquine and possibly to oltipraz are also available. All of these strains are currently maintained in the laboratory in snails and mice, thus providing for the first time an opportunity for indepth comparative studies. Preliminary data indicates that S. haematobium strains resistant to metrifonate may be occurring in Kenya. This problem could poise great difficulty in the eventual development of antischistosomal agents. Biomphalaria glabrata from Puerto Rico and Brazil were found to be susceptible to drug-resistant S. mansoni from each country.