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

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Abstract

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.

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New diagnostic tools in schistosomiasis.

J Utzinger, S L Becker, L Van Lieshout … (2015)

Schistosomiasis is a water-based parasitic disease that affects over 250 million people. Control efforts have long been in vain, which is one reason why schistosomiasis is considered a neglected tropical disease. However, since the new millennium, interventions against schistosomiasis are escalating. The initial impetus stems from a 2001 World Health Assembly resolution, urging member states to scale-up deworming of school-aged children with the anthelminthic drug praziquantel. Because praziquantel is safe, efficacious and inexpensive when delivered through the school platform, diagnosis before drug intervention was deemed unnecessary and not cost-effective. Hence, there was little interest in research and development of novel diagnostic tools. With the recent publication of the World Health Organization (WHO) Roadmap to overcome the impact of neglected tropical diseases in 2020, we have entered a new era. Elimination of schistosomiasis has become the buzzword and this has important ramifications for diagnostic tools. Indeed, measuring progress towards the WHO Roadmap and whether local elimination has been achieved requires highly accurate diagnostic assays. Here, we introduce target product profiles for diagnostic tools that are required for different stages of a schistosomiasis control programme. We provide an update of the latest developments in schistosomiasis diagnosis, including microscopic techniques, rapid diagnostic tests for antigen detection, polymerase chain reaction (PCR) assays and proxy markers for morbidity assessments. Particular emphasis is placed on challenges and solutions for new technologies to enter clinical practice.

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Tools for diagnosis, monitoring and screening of Schistosoma infections utilizing lateral-flow based assays and upconverting phosphor labels.

Paul Corstjens, Claudia de Dood, Dieuwke Kornelis … (2014)

The potential of various quantitative lateral flow (LF) based assays utilizing up-converting phosphor (UCP) reporters for the diagnosis of schistosomiasis is reviewed including recent developments. Active infections are demonstrated by screening for the presence of regurgitated worm antigens (genus specific polysaccharides), whereas anti-Schistosoma antibodies may indicate ongoing as well as past infections. The circulating anodic antigen (CAA) in serum or urine (and potentially also saliva) is identified as the marker that may allow detection of single-worm infections. Quantitation of antigen levels is a reliable method to study effects of drug administration, worm burden and anti-fecundity mechanisms. Moreover, the ratio of CAA and circulating cathodic antigen (CCA) is postulated to facilitate identification of either Schistosoma mansoni or Schistosoma haematobium infections. The UCP-LF assays allow simultaneous detection of multiple targets on a single strip, a valuable feature for antibody detection assays. Although antibody detection in endemic regions is not a useful tool to diagnose active infections, it gains potential when the ratio of different classes of antibody specific for the parasite/disease can be determined. The UCP-LF antibody assay format allows this type of multiplexing, including testing a linear array of up to 20 different targets. Multiple test spots would allow detection of specific antibodies, e.g. against different Schistosoma species or other pathogens as soil-transmitted helminths. Concluding, the different UCP-LF based assays for diagnosis of schistosomiasis provide a collection of tests with relatively low complexity and high sensitivity, covering the full range of diagnostics needed in control programmes for mapping, screening and monitoring.

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Schistosomiasis is more prevalent than previously thought: what does it mean for public health goals, policies, strategies, guidelines and intervention programs?

Daniel G. Colley, Tamara S. Andros, Carl Campbell (2017)

Mapping and diagnosis of infections by the three major schistosome species (Schistosoma haematobium, S. mansoni and S. japonicum) has been done with assays that are known to be specific but increasingly insensitive as prevalence declines or in areas with already low prevalence of infection. This becomes a true challenge to achieving the goal of elimination of schistosomiasis because the multiplicative portion of the life-cycle of schistosomes, in the snail vector, favors continued transmission as long as even a few people maintain low numbers of worms that pass eggs in their excreta. New mapping tools based on detection of worm antigens (circulating cathodic antigen – CCA; circulating anodic antigen – CAA) in urine of those infected are highly sensitive and the CAA assay is reported to be highly specific. Using these tools in areas of low prevalence of all three of these species of schistosomes has demonstrated that more people harbor adult worms than are regularly excreting eggs at a level detectable by the usual stool assay (Kato-Katz) or by urine filtration. In very low prevalence areas this is sometimes 6- to10-fold more. Faced with what appears to be a sizable population of “egg-negative/worm-positive schistosomiasis” especially in areas of very low prevalence, national NTD programs are confounded about what guidelines and strategies they should enact if they are to proceed toward a goal of elimination. There is a critical need for continued evaluation of the assays involved and to understand the contribution of this “egg-negative/worm-positive schistosomiasis” condition to both individual morbidity and community transmission. There is also a critical need for new guidelines based on the use of these more sensitive assays for those national NTD programs that wish to move forward to strategies designed for elimination. Electronic supplementary material The online version of this article (doi:10.1186/s40249-017-0275-5) contains supplementary material, which is available to authorized users.

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Journal

Journal ID (nlm-ta): Mem Inst Oswaldo Cruz

Journal ID (iso-abbrev): Mem. Inst. Oswaldo Cruz

Journal ID (publisher-id): mioc

Title: Memórias do Instituto Oswaldo Cruz

Publisher: Instituto Oswaldo Cruz, Ministério da Saúde

ISSN (Print): 0074-0276

ISSN (Electronic): 1678-8060

Publication date (Electronic): 28 March 2019

Publication date Collection: 2019

Volume: 114

Electronic Location Identifier: e180478

Affiliations

[1 ]Fundação Oswaldo Cruz-Fiocruz, Instituto René Rachou, Biologia do Schistosoma mansoni e sua interação com o hospedeiro, Belo Horizonte, MG, Brasil

[2 ]Fundação Oswaldo Cruz-Fiocruz, Instituto René Rachou, Grupo de Pesquisas Clínicas e Políticas Públicas em Doenças Infecciosas e Parasitárias, Belo Horizonte, MG, Brasil

[3 ]Universidade Federal de Ouro Preto, Laboratório de Enzimologia e Proteômica, Ouro Preto, MG, Brasil

[4 ]University of Georgia, College of Veterinary Medicine, Department of Infectious Diseases, Athens, GA, United States of America

[5 ]Old Dominion University, Department of Biological Sciences, Norfolk, VA, United States of America

Author notes

+ Corresponding author: vmoraes@ 123456uga.edu , vanessasmabp@ 123456gmail.com

VSM - Conceptualisation, writing (original draft, review, and editing); LMS and DAH - supervision, writing (review and editing) and visualisation; LMVS, WCB and RFGQ - writing (draft, review, and editing); ALTR and PMZ - conceptualisation, supervision, writing (review and editing), and visualisation.

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Vanessa Silva-Moraes http://orcid.org/0000-0003-2991-7210

Article

Other ID: 00200

DOI: 10.1590/0074-02760180478

PMC ID: 6440364

PubMed ID: 30942278

SO-VID: d2a1ebbd-3a13-4382-bdcb-6bac3ef98e4d

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This is an open-access article distributed under the terms of the Creative Commons Attribution License

History

Date received : 12 October 2018

Date accepted : 21 February 2019

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

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Most cited references 116

New diagnostic tools in schistosomiasis.

Tools for diagnosis, monitoring and screening of Schistosoma infections utilizing lateral-flow based assays and upconverting phosphor labels.

Schistosomiasis is more prevalent than previously thought: what does it mean for public health goals, policies, strategies, guidelines and intervention programs?

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