Diagnosis of Schistosoma mansoni infections: what are the choices in Brazilian low-endemic areas?

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.

Serological proteomic screening and evaluation of a recombinant egg antigen for the diagnosis of low-intensity Schistosoma mansoni infections in endemic area in Brazil.

BACKGROUND: Despite decades of use of control programs, schistosomiasis remains a global public health problem. To further reduce prevalence and intensity of infection, or to achieve the goal of elimination in low-endemic areas, there needs to be better diagnostic tools to detect low-intensity infections in low-endemic areas in Brazil. The rationale for development of new diagnostic tools is that the current standard test Kato-Katz (KK) is not sensitive enough to detect low-intensity infections in low-endemic areas. In order to develop new diagnostic tools, we employed a proteomics approach to identify biomarkers associated with schistosome-specific immune responses in hopes of developing sensitive and specific new methods for immunodiagnosis. METHODS AND FINDINGS: Immunoproteomic analyses were performed on egg extracts of Schistosoma mansoni using pooled sera from infected or non-infected individuals from a low-endemic area of Brazil. Cross reactivity with other soil-transmitted helminths (STH) was determined using pooled sera from individuals uniquely infected with different helminths. Using this approach, we identified 23 targets recognized by schistosome acute and chronic sera samples. To identify immunoreactive targets that were likely glycan epitopes, we compared these targets to the immunoreactivity of spots treated with sodium metaperiodate oxidation of egg extract. This treatment yielded 12/23 spots maintaining immunoreactivity, suggesting that they were protein epitopes. From these 12 spots, 11 spots cross-reacted with sera from individuals infected with other STH and 10 spots cross-reacted with the negative control group. Spot number 5 was exclusively immunoreactive with sera from S. mansoni-infected groups in native and deglycosylated conditions and corresponds to Major Egg Antigen (MEA). We expressed MEA as a recombinant protein and showed a similar recognition pattern to that of the native protein via western blot. IgG-ELISA gave a sensitivity of 87.10% and specificity of 89.09% represented by area under the ROC curve of 0.95. IgG-ELISA performed better than the conventional KK (2 slides), identifying 56/64 cases harboring 1-10 eggs per gram of feces that were undiagnosed by KK parasitological technique. CONCLUSIONS: The serological proteome approach was able to identify a new diagnostic candidate. The recombinant egg antigen provided good performance in IgG-ELISA to detect individuals with extreme low-intensity infections (1 egg per gram of feces). Therefore, the IgG-ELISA using this newly identified recombinant MEA can be a useful tool combined with other techniques in low-endemic areas to determine the true prevalence of schistosome infection that is underestimated by the KK method. Further, to overcome the complexity of ELISA in the field, a second generation of antibody-based rapid diagnostic tests (RDT) can be developed.

Altenusin, a biphenyl isolated from the endophytic fungus Alternaria sp., inhibits trypanothione reductase from Trypanosoma cruzi.

Parasitic protozoan species belonging to the genera Trypanosoma and Leishmania are the etiological agents of several diseases in tropical areas of the world, for which there is an urgent need for effective and affordable treatment. In this regard, we are screening the Brazilian biodiversity, especially its flora and mycota, for natural products that could serve as leads for drug development against these diseases. Trypanothione reductase (TR) is an enzyme involved in the protection of Trypanosoma and Leishmania species against oxidative stress, and is considered to be a validated drug target. The endophytic fungus Alternaria sp. (UFMGCB55) was isolated from the plant Trixis vauthieri DC (Asteraceae), known to contain trypanocidal compounds. The organic extract of the culture of Alternaria sp. was able to inhibit TR by 99%, when tested at 20 microg mL(-1). Fractionation of the extract identified altenusin, a biphenyl derivative with an IC50 value of 4.3+/-0.3 microM in the TR assay. This compound is the first in its class to have shown TR inhibitory activity, opening new perspectives for the design of more effective derivatives that could serve as drug leads for new chemotherapeutic agents to treat trypanosomiasis and leishmaniasis.

Diagnosis of Schistosoma mansoni infections: what are the choices in Brazilian low-endemic areas?

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.

Budgetary impact of diagnostic tests for visceral leishmaniasis in Brazil / Impacto orçamentário dos testes diagnósticos para leishmaniose visceral no Brasil

O estudo teve como objetivo estimar os custos financeiros da incorporação e/ou substituição dos testes diagnósticos para a leishmaniose visceral (LV) humana no Brasil. A análise foi realizada na perspectiva do Sistema Único de Saúde (SUS) ao longo de três anos. Foram avaliados seis testes diagnósticos: reação de imunofluorescência indireta (RIFI), teste rápido IT LEISH, exame parasitológico de aspirado de medula óssea, teste de aglutinação direta DAT-LPC padronizado pelo Laboratório de Pesquisas Clínicas do Instituto René Rachou, Fundação Oswaldo Cruz, teste rápido Kalazar Detect e reação em cadeia da polimerase (PCR). Os parâmetros utilizados foram o número de casos suspeitos de LV notificados ao Ministério da Saúde em 2014 e o custo direto dos testes diagnósticos. Os custos do diagnóstico de casos suspeitos de LV ao longo de três anos usando o RIFI e DAT-LPC foram estimados em USD 280.979,91 e USD 121.371,48, respectivamente. De acordo com a análise, comparado ao uso do RIFI, a incorporação do DAT-LPC pelo SUS resultaria numa economia de USD 159.608,43. Com relação ao impacto dos testes rápidos, o uso do IT LEISH resultou em economia de USD 21.708,72 ao longo de três anos. Comparado ao exame parasitológico, o diagnóstico com PCR resultou em economia de USD 3.125.068,92 ao longo de três anos. Neste estudo, a substituição do RIFI pelo DAT-LPC mostrou ser financeiramente vantajosa. Além disso, a substituição do teste rápido Kalazar Detect com o IT LEISH em 2015 foi economicamente apropriada, e a substituição do exame parasitológico pela PCR está economicamente indicada.

Study of implementation and direct cost estimates for diagnostic tests for human visceral leishmaniasis in an urban area in Brazil / Estudo da implantação e estimativas de custo direto de testes diagnósticos para leishmaniose visceral humana em uma área urbana no Brasil

Este trabalho relata o processo e os custos da implantação de dois testes para descentralizar o diagnóstico da leishmaniose visceral (LV) em um município endêmico no Brasil: um teste rápido (IT LEISH) e um teste de aglutinação direta (DAT-LPC). A implantação iniciou com o treinamento dos profissionais de saúde do município na realização dos testes diagnósticos. Os itens incluídos nas estimativas de custo das capacitações foram a remuneração proporcional de todos os profissionais envolvidos e os custos diretos dos testes usados. O estudo foi conduzido entre novembro de 2011 e novembro de 2013. Durante esse período, 17 capacitações foram realizadas e 175 profissionais treinados. O custo relacionado a cada profissional de saúde capacitado na realização do IT LEISH foi de US$ 7,13 e na realização do DAT-LPC, de US$ 9,93. O custo direto do IT LEISH e do DAT-LPC foi estimado em US$ 6,62 e US$ 5,44, respectivamente. Esta primeira avaliação da implantação desses dois testes aponta para a viabilidade da descentralização de ambos os métodos, que aumentam o acesso ao diagnóstico da LV no Brasil.