[IgM-ELISA for diagnosis of schistosomiasis mansoni in low endemic areas]. / ELISA-IgM para diagnóstico da esquistossomose mansoni em área de baixa endemicidade.

An immunoenzymatic method for the detection of IgM antibodies (IgM-ELISA) against a fraction of Schistosoma mansoni adult worm antigen, soluble in trichloroacetic acid (TCA-soluble fraction), was evaluated for epidemiological purposes in low endemic areas for schistosomiasis. Blood samples on filter paper were collected from a population living in the municipality of Pedro de Toledo, São Paulo State, and submitted to IgM-ELISA. The results were compared to those obtained by the IgM-immunofluorescence test (IgM-IFT) and the Kato-Katz parasitological method. Positive rates of 36.8%, 33.5%, and 1.6% were obtained respectively by the IgM-ELISA, IgM-IFT, and Kato-Katz methods. The geometric mean obtained by the parasitological method was 40.9 eggs per gram of feces (epg). The nearly perfect agreement observed between the two serological tests (Kappa index of 0,89) indicates good diagnostic performance by the evaluated test. IgM-ELISA is a potentially useful method for diagnosis of schistosomiasis in individuals with low worm burden.

IgM-immunofluorescence test as a diagnostic tool for epidemiologic studies of Schistosomiasis in low endemic areas.

The high sensitivity and the ability to diagnose schistosomiasis in a very early phase after infection have indicated the detection of IgM antibodies to Schistosoma mansoni gut antigens by the immunofluorescence test (IgM-IFT) as a useful serological test for epidemiological studies in low endemic areas. When applied in a follow-up study for two years, higher rates of seroconversion from IFT negative to positive were observed during the summer months, suggesting seasonal transmission of schistosomiasis in the rural area of the municipality of Itariri (São Paulo, Brazil). In each survey, blood samples from about 600 schoolchildren were collected on filter paper and submitted to IgM-IFT. When the blood samples were classified for the IgM antibody levels, according to the intensity of fluorescent reaction observed at fluorescence microscopy, and correlated to the egg counts in the Kato-Katz positive patients, no association was observed. This observation might suggest that the intensity of fluorescence observed in the IgM-IFT, as an indicator of IgM antibody levels, could not be an useful seroepidemiological marker for classifying areas of low endemicity according to degrees of infection.

Variation in response of Schistosoma mansoni strains to Schistosomicides

A cepa BH de S. mansoni foi suscetível ao hycanthone (1 X 80 mg/Kg), oxamniquine (1 X 100 mg/Kg), niridazole (5 X 100 mg/Kg), praziquantel (1 X 100 mg/Kg), oltipraz (5 X 125 mg/Kg) e amoscanato (1 X 300 mg/Kg). Assim, essa cepa do trematódeo é importante como referência nos estudos de quimioterapia experimental. Por outro lado, a cepa MPR-1 apresentou resistência ao oxamniquine e/ou hycanthone. Foi possível constatar em uma cepa resistência parcial ao oltipraz

Strain variation in the infectivity of Schistosoma mansoni for Biomphalaria glabrata

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 infecçäo 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 desenvolveram bem e infectaram mais de 90% dos exemplares de B. glabrata portorriquenhos. Entre os resultados, ressalta-se que cepas resistentes a esquistossomicidas poderäo ser utilizadas por pacientes em diferentes áreas geográficas como Brasil e Porto Rico

Suscetibilidade de Biomphalaria glabrata, B. straminea e B. tenagophila a diferentes cepas de Schistosoma mansoni / Susceptibility of Biomphalaria glabrata, B. straminea and B. tenagophila to different strains of Schistosoma mansoni

Em condiçöes 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 simpática (MAP) e com 5 alopátricas do Estado de Säo Paulo (PTH, VPH, OuH, PTR e VPR). B. glabrata paulista mostrou altas taxas de infecçäo com as cepas MAP, VPR e OuH do trematódeo. Quatro % dos exemplares B. straminea de Säo 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, näo 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 säo importantes na disseminaçäo da esquistossomose mansônica

Altered Response of Strain of Schistosoma mansoni to Oxamniquine and Praziquantel

The susceptibility of a fourth generation Ouh strain (Paranapanema Valley, Säo Paulo, Brazil) of Schistosoma mansoni to oxamniquine (OXA) and praziquantel (PZQ) was studied. Ten groups of 13 female albino mice each were infected with 70 cercariae per animal. These mice were medicated orally on the 50th day after infection. Five groups were given OXA doses of 0, 100, 200, 300 and 400 mg/kg (single doses) and the rest were treated with PZQ doses of 0, 100, 200, and 250 mg/kg/5 days. Each group was sub-divided: 8 animals underwent perfusion after 15 days treatment, 5 mice followed up for oviposition and their feces were tested every 15 days for miracidia hatching. The efficacy of the OXA doses of 100 and 200 mg/kg was 66 percent and 91.4 percent, respectively and for the 100 mg/kg PZQ dose it was 90.1 percent. The follow-up groups with 100 and 200 mg/kg of OXA and PZQ, 100 and 150 mg/kg, showed that they re-established the oviposition after a period of 60 to 75 days of treatment. The ED50 was 69.6mg/kg OXA and 39.4 mg/kg PZQ. The results show the tolerance of the Ouh strain to a dose of 100 mg with both drugs and they appoint the need for a dose review during the follow up of the oviposition and in monitoring phenomena in the field

Controle da esquistossomose mansônica em área de baixa transmissao / Control of schistosomiasis mansoni in a low transmission area

The schistosomiasis is transmitted by Biomphalaria tenagophila in our study area (Pedro de Toledo, Sao Paulo, Brazil). From 1980 to 1990 epidemiological surveys in a population of 4.000 inhabitants, has shown that: prevalence Kato-Katz (KKT), immunofluorescence (FT) and intradermal (IDT) techniques were 22.8%, 55.5% and 51.8% respectively; intensity of infection was low, 58.5 eggs per gram of faeces (epg); there were no symptomatic cases; prevalences were higher in mates, children and rural zone; index of potential contamination was 57.5% in the age group 5 to 20 years; 2/3 of patients were autochtonous; cases were no-randomly aggregated; transmission was focal and only 0.4% of snails were infected; water contacts through recreation showed the most important odds ratio; knowledge, attitudes and practices were satisfatory. From the epidemiological control findings a control programme was carried out; yearly faeces exams, chemotherapy, molluscocide, health education and sanitation. Thus, the prevalence decreased sharply to 3.3% and intensity of infection to 30.3 epg; the incidence rates ranged between 0.4% and 2.5% annualy; the sanitation became better and the youngsters were the main target in prophylaxis. To improve control, immunodiagnosis has to be conducted and the involvment of the population should be increase. However, we cannot forget that re-infection and the involvment of the population should be increase. However, we cannot forget that re-infection, therapeutic failure, etc, could play a major role in the maintnance this residual prevalence

Drug resistance in Schistosomiasis: a review

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.

Response of drug resistant isolates of Schistosoma mansoni to antischistosomal agents

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

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.

ELISA-IgM para diagnóstico da esquistossomose mansoni em área de baixa endemicidade / IgM-ELISA for diagnosis of schistosomiasis mansoni in low endemic areas

Um método imunoenzimático para detecçäo de anticorpos IgM (ELISA-IgM) contra uma fraçäo do extrato total de vermes de Schistosoma mansoni, solúvel em ácido tricloro acético (fraçäo TCA-solúvel) foi avaliado para fins epidemiológicos, em área de baixa endemicidade para esquistossomose. Amostras de sangue em papel de filtro, coletadas de uma populaçäo residente no município de Pedro de Toledo, Estado de São Paulo, foram submetidas ao ELISA-IgM e os resultados, analisados comparativamente aos obtidos pela RIFI-IgM e pelo exame parasitológico de fezes Kato-Katz. Obteve-se 36,8 por cento de positividade pelo ELISA-IgM, 33,5 por cento pela RIFI-IgM e 1,6 por cento pelo Kato-Katz, que indicou uma média geométrica de 40,9 ovos por grama de fezes (opg). A concordância de resultados, quase perfeita (índice Kappa de 0,89), observada entre os dois métodos sorológicos, indica um bom desempenho diagnóstico do teste em avaliaçäo. O ELISA-IgM constitui-se em um método potencialmente útil para fins diagnósticos da esquistossomose, em indivíduos com baixa carga parasitária

IgM antibodies to Schistosoma mansoni gut-associated antigens for the study of Schistosomiasis transmission in Ribeiräo Pires, Säo Paulo

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 Ribeiräo Pires, in the metropolitan area of the capital of the State of Säo 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 per cent, 5.8 per cent, 6.2 per cent, 2.9 per cent and 3.3 per cent were obtained. These indices were 7 to 10 times higher than the parasitological prevalence indices of 0.5 per cent, 0.5 per cent, 0.7 per cent, 0.4 per cent and 0 per cent 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.

Immunofluorescence test on Schistosoma mansoni worm paraffin sections (IgM-IFT) for the study of shistosomiasis transmission in Campinas, Säo Paulo, Brazil

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 shistosomiasis in an urban area in Campinas. About 400 school children 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 per cent, 4.3 per cent, 3.6 per cent, 2.9 per cent and 3.4 per cent were obtained in five surveys carried out. S. mansoni eggs were detected in only one child out of the 225 children (0.4 per cent) 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 children, 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.

IgM-immunofluorescence test as a diagnostic Tool for epidemiologic studies of Schistosomiasis in low endemic areas

The high sensitivity and the ability to diagnose schistosomiasis in a very early phase after infection have indicated the detection of IgM antibodies to Schistosoma mansoni gut antigens by the immunofluorescence test (IgM-IFT) as a useful serological test for epidemiological studies in low endemic areas. When applied in a follow-up study for two years, higher rates of seroconversion from IFT negative to positive were observed during the summer months, suggesting seasonal transmission of schistosomiasis in the rural area of the municipality of Itariri (Säo Paulo, Brazil). In each survey, blood samples from about 600 schoolchildren were collected on filter paper and submitted to IgM-IFT. When the blood samples were classified for the IgM antibody levels, according to the intensity of fluorescent reaction observed at fluorescence microscopy, and correlated to the egg counts in the Kato-Katz positive patients, no association was observed. This observation might suggest that the intensity of fluorescence observed in the IgM-IFT, as an indicator of IgM antibody levels, could not be an useful seroepidemiological marker for classifying areas of low endemicity according to degrees of infection

Schistosomiasis mansoni: follow-up of control program based on parasitologic and serologic methods in a brazilian community of low endemicity

A field survey on schistosomiais was carried out in 1998, in the municipality of Pedro de Toledo, a low endemic area in the state of Sä¯áPaulo, Brazil. According to the parasitologic Kato-Katz method, the prevalence rate was 1.6 percent, with an infection intensity of 40.9 eggs per gram of stool. By the immunofluorescence test (IFT) for detection of IgG and IgM antibodies in the serum, IgG-IFT and IgM-IFT, respectively, prevalence indices of 33.2 percent and 33.5 percent were observed. To assess the impact of the schistosomiasis control program in the area, parasitologic and serologic data obtained in 1998, analyzed according to the age, sex, and residence zone, were compared to previous data obtained in a epidemiologic study carried out in 1980, when prevalence indices were of 22.8 percent and 55.5 percent, respectively by Kato-Katz and IgG-IFT. A significant fall of the prevalence was observed, indicating that the control measures were effective. Nonetheless, residual transmission was observed, demonstrating the need for a joint effort to include new approaches for better understanding the real situation and improving the control of the disease in low endemic areas

Coprotest quantitativo: quantificação de ovos de helmintos em amostras fecais utilizando-se sistema de diagnóstico comercial / Quantitative Coprotest®: quantification of helminth eggs in fecal samples by commercial diagnostic kit

A técnica coproparasitológica de concentração em formol acetato de etila foi empregada para a quantificaçäo 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 aplicaçäo viável, fornecendo resultados comparáveis a outros métodos quantitativos já descritos na literatura

A comparative epidemiologic study of specific antibodies (IgM and IgA) and parasitological findings in an endemic area of low transmission of Schistosoma mansoni

O potencial diagnostico dos anticorpos IgM e IgA contra antigenos do tubo digestivo do Schistosoma mansoni detectados através da reaçäo de imunofluorescencia indireta utilizando-se cortes parafinados de vermes adultos, foi avaliado, comparativamente aos resultados do exame parasitologico de fezes, para fins epidemiológicos em areas de baixa endemicidade para a esquistossomose. Amostras de sangue em papel de filtro foram coletadas de escolares, residindo em duas localidades diferentes dentro do municipio de Itariri (Sao Paulo, Brasil), com caracteristicas epidemiologicas distintas em relaçäo a esquistossomose. Os dados parasitológicos e sorológicos foram comparados aos obtidos com um outro grupo de escolares, residentes em uma area näo endemica para esquistossomose. Os resultados demonstraram a falta de sensibilidade do método parasitológico para detecçäo de individuos com baixa carga parasitária e indicam a potencialidade do método sorológico como importante instrumento a ser incorporado aos programas de controle e de vigilância da esquistossomose, para verificaçäo da real situaçäo da esquistossomose em areas de baixa endemicidade

The epidemiology and control of schistosomiasis mansoni where Biomphalaria tenagophila is the snail host

Desde 1980, está-se estudando a epidemiologia e o controle da esquistossomose mansônica no Município de Pedro de Toledo (Estado de Säo Paulo, Brasil). Em 1980 a prevalência avaliada por exame de fezes (métodos de Kato-Katz) foi de 22,8%. Estatisticamente, ao nível de 5%, näo houve diferença nas prevalências observadas nas zonas rural e urbana. A intensidade de infecçäo foi baixa (média geométrica de 58,5 ovos por grama de fezes). As maiores prevalências e intensidades de infecçäo foram registradas na faixa etária de 5 a 29 anos. Geralmente a transmissäo 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 avaliaçäo dos dados de 1980, resultando em diminuiçäo acentuada da prevalência de 22,8% em 1980 para 6%. Esta prevalência residual vem se mantendo ate 1987. Agora iniciamos estudos para investigar as possíveis causas dessa prevalência residual.

Failure at inducing resistance to schistosomicidal drugs in a brazilian human strain of Schistosoma mansoni

No presente estudo, realizou-se uma tentativa de induçäo de resistência a 3 drogas esquistossomicidas em uma cepa brasileira de S. mansoni, segundo o esquema de induçäo de resistência tipo II preconizado por Jansma et al. em 1977. Houve insucesso nas 3 tentativas realizadas. A geraçäo parental tratada com a droga durante o estágio imaturo do verme mostrou-se menos suscetível aos quimioterápicos do que as geraçöes F1 e F2 do verme. Uma hipótese é levantada para a explicaçäo do fato

Genetic complementation analysis of two independently isolated hycanthone-resistant strains of Schistosoma mansoni

The objective of this study is to determine whether various hycanthone resistant strains of schistosomes which have been independently isolated are all affected in the same gene. A strain obtained from a Brazilian patient was compared with a strain of Puerto Rican origin selected in the laboratory. If the mutation conferring resistance involved two different genes, one would expect that the progeny of a cross between the two strains would show complementation, i.e. it would be sensitive to the drug. We have performed such a cross and obtained F1 hybrid worms wich were essentially all resistant, thus suggesting that the mutation conferring resistance in the two strains involves the same gene