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Open Access Research article

Field evaluation of a new antibody-based diagnostic for Schistosoma haematobium and S. mansoni at the point-of-care in northeast Zimbabwe

Norman Nausch15, Emily M Dawson2*, Nicholas Midzi36, Takafira Mduluza4, Francisca Mutapi1 and Michael J Doenhoff2

Author Affiliations

1 Institute of Immunology and Infection Research, Centre for Immunity, Infection and Evolution, Ashworth Laboratories, West Mains Road, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK

2 School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK

3 National Institutes of Health Research, Box CY 573 Causeway, Harare, Zimbabwe

4 Department of Biochemistry, University of Zimbabwe, P.O. Box 167Mount Pleasant, Harare, Zimbabwe

5 Current Address: Pediatric Pneumology and Infectious Diseases Group, Department of General Pediatrics, Neonatology, and Pediatric Cardiology, University Children’s Hospital, 40225 Duesseldorf, Germany

6 Current Address: Department of Medical Microbiology, University of Zimbabwe, P.O. Box A178 Avondale, Harare, Zimbabwe

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BMC Infectious Diseases 2014, 14:165  doi:10.1186/1471-2334-14-165

Published: 26 March 2014

Abstract

Background

Rapid diagnostic tests (RDTs) for use at the point-of-care (POC) are likely to become increasingly useful as large-scale control programmes for schistosomiasis get underway. Given the low sensitivity of the reference standard egg count methods in detecting light infections, more sensitive tests will be required to monitor efforts aimed at eliminating schistosomiasis as advocated by the World Health Assembly Resolution 65.21 passed in 2012.

Methods

A recently developed RDT incorporating Schistosoma mansoni cercarial transformation fluid (SmCTF) for detection of anti-schistosome antibodies in human blood was here evaluated in children (mean age: 7.65 years; age range: 1-12 years) carrying light S. mansoni and S. haematobium infections in a schistosome-endemic area of Zimbabwe by comparison to standard parasitological techniques (i.e. the Kato-Katz faecal smear and urine filtration). Enzyme-linked immunosorbent assays (ELISAs) incorporating S. haematobium antigen preparations were also employed for additional comparison.

Results

The sensitivity of the SmCTF-RDT compared to standard parasitological methods was 100% while the specificity was 39.5%. It was found that the sera from RDT “false-positive” children showed significantly higher antibody titres in IgM-cercarial antigen preparation (CAP) and IgM-soluble egg antigen (SEA) ELISA assays than children identified by parasitology as “true-negatives”.

Conclusions

Although further evaluations are necessary using more accurate reference standard tests, these results indicate that the RDT could be a useful tool for the rapid prevalence-mapping of both S. mansoni and S. haematobium in schistosome-endemic areas. It is affordable, user-friendly and allows for diagnosis of both schistosome species at the POC.

Keywords:
Schistosomiasis; Diagnosis; Antibody-detection; Point-of-care; Neglected tropical disease