The population of Brazil is currently characterised by many individuals harbouring low-intensity Schistosoma mansoni infections. The Kato-Katz technique is the diagnostic method recommended by the World Health Organization (WHO) to assess these infections, but this method is not sensitive enough in the context of low egg excretion. In this regard, potential alternatives are being employed to overcome the limits of the Kato-Katz technique. In the present review, we evaluated the performance of parasitological and immunological approaches adopted in Brazilian areas. Currently, the diagnostic choices involve a combination of strategies, including the utilisation of antibody methods to screen individuals and then subsequent confirmation of positive cases by intensive parasitological investigations.

Current schistosomiasis control strategies are largely based on chemotherapeutic agents and a limited number of drugs are available today. Praziquantel (PZQ) is the only drug currently used in schistosomiasis control programs. Unfortunately, this drug shows poor efficacy in patients during the earliest infection phases. The effects of PZQ appear to operate on the voltage-operated Ca2+channels, which are located on the external Schistosoma mansoni membrane. Because some Ca2+channels have dihydropyridine drug class (a class that includes nifedipine) sensitivity, an in vitro analysis using a calcium channel antagonist (clinically used for cardiovascular hypertension) was performed to determine the antischistosomal effects of nifedipine on schistosomula and adult worm cultures. Nifedipine demonstrated antischistosomal activity against schistosomula and significantly reduced viability at all of the concentrations used alone or in combination with PZQ. In contrast, PZQ did not show significant efficacy when used alone. Adult worms were also affected by nifedipine after a 24 h incubation and exhibited impaired motility, several lesions on the tegument and intense contractility. These data support the idea of Ca2+channels subunits as drug targets and favour alternative therapeutic schemes when drug resistance has been reported. In this paper, strong arguments encouraging drug research are presented, with a focus on exploring schistosomal Ca2+channels.

Schistosomiasis diagnosis is based on the detection of eggs in the faeces, which is laborious and lacks sensitivity, especially for patients with a low parasite burden. Immunological assays for specific antibody detection are available, but they usually demonstrate low sensitivity and/or specificity. In this study, two simple immunological assays were evaluated for the detection of soluble Schistosoma mansoni adult worm preparation (SWAP) and egg-specific IgGs. These studies have not yet been evaluated for patients with low parasite burdens. Residents of an endemic area in Brazil donated sera and faecal samples for our study. The patients were initially diagnosed by a rigorous Kato-Katz analysis of 18 thick smears from four different stool samples. The ELISA-SWAP was successful for human diagnosis with 90% sensitivity and specificity, confirming the Kato-Katz diagnosis with nearly perfect agreement, as seen by the Kappa index (0.85). Although the ELISA-soluble S. mansoni egg antigen was 85% sensitive, it exhibited low specificity (80%; Kappa index: 0.75) and was more susceptible to cross-reactivity. We believe that immunological assays should be used in conjunction with Kato-Katz analysis as a supplementary tool for the diagnosis of schistosomiasis for patients with low infection burdens, which are usually hard to detect.

IntroductionThe diagnosis of schistosomiasis mansoni on early stages of infection is important to prevent late morbidity. A simple, cheap, sensitive and specific assay for routine diagnosis of schistosome infection based on the detection of specific IgG for schistosomula tegument antigens (ELISA-SmTeg) was developed by our group.MethodsWe describe here an acute outbreak involving a travel group of 80 individuals from a non-endemic area of the State of Minas Gerais, Brazil. These individuals were in contact with a freshwater pool where Biomphalaria glabrata was found. Results obtained from our new methodology were compared to IgG antibody titers against soluble worm antigenic preparation (SWAP) by ELISA and, also to parasitological examination, nuclear magnetic resonance and clinical findings.ResultsELISA-SmTeg was capable of detecting 64 positive cases among the 80 individuals participating at the survey with a positivity ratio of 80% and a higher sensitivity than ELISA-SWAP that was only sensitive for 56% of positive cases. Besides, a significant correlation was found for the severity of the infection and the specific IgG titers against SmTeg.ConclusionsOur data showed that ELISA-SmTeg might serve as the initial diagnostic tool for acute stages of the infection in community-based helminth control programs or for the surveillance of individuals from non-endemic areas.

A detecção da infecção pelo helminto Schistosoma mansoni quando realizada nas fases iniciais, especialmente antes da oviposição nos tecidos do hospedeiro, pode impedir de forma eficiente o desenvolvimento de graves lesões patológicas. Baseado nisto, foi desenvolvido um ensaio imunoenzimático indireto para detecção de anticorpos IgG específicos contra antígenos de esquistossômulos (ELISA-SmTeg). Este ensaio foi aplicado em amostras sorológicas de camundongos não infectados, da mesma forma que de camundongos recentemente infectados, após sete e 15 dias de infecção. Os resultados foram comparados com o número de vermes adultos obtidos por perfusão do sistema hepático murino 50 dias pós-infecção. A sensibilidade e a especificidade do novo método, denominado ELISA-SmTeg, foram de 100% (p = 0,0032, 0,0048, respectivamente, durante sete e 15 dias de infecção) com um valor de corte de 0,15 (p = 0,0002). Nossos resultados mostraram que um ensaio de baixo custo, que utiliza antígenos de fácil obtenção, é capaz de discriminar a esquistossomose mansoni em modelo experimental de forma precoce, incluindo sete dias pós-infecção.

If Schistosoma mansoni infection could be detected in its early stages, especially before the egg deposition in the host tissues, the development of severe pathologic lesions could be efficiently prevented. We therefore developed an indirect enzyme-linked immunosorbent assay based on the detection of specific IgG against schistosomula antigens (ELISA-SmTeg). The assay was applied in sera samples from non-infected and infected mice collected seven and 15 days post-infection. The results were compared to the number of adult worms obtained by perfusion of the murine hepatic system 50 days post-infection. The sensitivity and specificity of the ELISA-SmTeg were 100% (p = 0.0032 and 0.0048 respectively for seven and 15 days of infection) with a cutoff value of 0.15 (p = 0.0002). Our findings show a novel low-cost serological assay using antigens which are easy to obtain, which was able to detect all the infected mice as early as seven days post-infection.

INTRODUÇÃO: A correlação entre o ensaio imunológico e o título de anticorpos serve como ferramenta para a determinação das diferentes fases da doença. MÉTODOS: Dois ensaios imunológicos simples para detecção de IgG específico para antígenos de vermes adultos e ovos do Schistosoma mansoni com amostras de soro murino foram padronizados e avaliados em nosso laboratório. Cinquenta camundongos negativos e positivos foram avaliados e os resultados obtidos por enzyme-linked immunosorbent assays (ELISA) foram comparados com o número de vermes adultos contados em tempos diferentes de infecção. RESULTADOS: Os dados mostraram que a ELISA com antígenos de vermes adultos (ELISA-SWAP) apresentou uma correlação satisfatória entre a absorbância obtida para os títulos de IgG e o número individual de vermes contados por perfusão do sistema porta hepático (R2=0,62). Adicionalmente, a ELISA-SWAP foi capaz de detectar diferencialmente amostras positivas com 30 e 60 dias de infecção (p=0,011 e 0,003, respectivamente), enquanto a ELISA com antígenos de ovos (ELISA-SEA) detectou amostras positivas com 140 dias de infecção (p=0,03). CONCLUSÕES: Estes dados mostram que o uso de antígenos diferentes em métodos imunológicos pode ser usado como ferramentas potenciais para a análise da evolução cronológica da infecção por S. mansoni na esquistossomose murina. Correlações com a esquistossomose humana devem ser discutidas.

INTRODUCTION: The correlation between the immunological assay and the antibody titer can offer a tool for the experimental analysis of different phases of the disease. METHODS: Two simple immunological assays for Schistosoma mansoni in mice sera samples based on specific IgG detection for worms soluble antigens and eggs soluble antigens were standardized and evaluated in our laboratory. Fifty mice were used in negative and positive groups and the results obtained by enzyme-linked immunosorbent assays (ELISA) assays were compared with the number of worms counted and the IgG titers at different times of infection. RESULTS: Data showed that ELISA using adult worm antigens (ELISA-SWAP) presented a satisfactory correlation between the absorbance value of IgG titers and the individual number of worms counted after perfusion technique (R²=0.62). In addition, ELISA-SWAP differentially detected positive samples with 30 and 60 days post infection (p=0.011 and 0.003, respectively), whereas ELISA using egg antigens (ELISA-SEA) detected samples after 140 days (p=0.03). CONCLUSIONS: These data show that the use of different antigens in immunological methods can be used as potential tools for the analysis of the chronological evolution of S. mansoni infection in murine schistosomiasis. Correlations with human schistosomiasis are discussed.