Abstract
BackgroundThe diagnosis of schistosomiasis currently relies on microscopic detection of schistosome eggs in stool or urine samples and serological assays. The poor sensitivity of standard microscopic procedures performed in routine laboratories, makes molecular detection methods of increasing interest. The aim of the study was to evaluate two in-house real-time Schistosoma PCRs, targeting respectively S. mansoni [Sm] and S. haematobium [Sh] in excreta, biopsies and sera as potential tools to diagnose active infections and to monitor treatment efficacy.MethodsSchistosoma PCRs were performed on 412 samples (124 urine, 86 stools, 8 biopsies, 194 sera) from patients with suspected schistosomiasis, before anti-parasitic treatment. Results were compared to microscopic examination and serological assays (enzyme-linked immunosorbent assay (ELISA), indirect haemagglutination (HA) and Western Blot (WB) assay).ResultsCompared to microscopy, PCRs significantly increased the sensitivity of diagnosis, from 4% to 10.5% and from 33.7% to 48.8%, for Sh in urine and Sm in stools, respectively. The overall sensitivity of PCR on serum samples was 72.7% and reached 94.1% in patients with positive excreta (microscopy). The specificity of serum PCR was 98.9%. After treatment, serum PCR positivity rates slowly declined from 93.8% at day 30 to 8.3% at day 360, whereas antibody detection remained positive after 1 year.ConclusionSchistosoma PCRs clearly outperform standard microscopy on stools and urine and could be part of reference methods combined with WB-based serology, which remains a gold standard for initial diagnosis. When serological assays are positive and microscopy is negative, serum PCRs provide species information to guide further clinical exploration. Biomarkers such as DNA and antibodies are of limited relevance for early treatment monitoring but serum PCR could be useful when performed at least 1 year after treatment to help confirm a cured infection.
Highlights
Schistosomiasis is a snail-borne parasitic disease of great concern worldwide, occurring mainly in Africa, Asia, and to a lesser degree in South America and the Middle East [1,2]
Serum PCR positivity rates slowly declined from 93.8% at day 30 to 8.3% at day 360, whereas antibody detection remained positive after 1 year
Schistosoma PCRs clearly outperform standard microscopy on stools and urine and could be part of reference methods combined with Western Blot (WB)-based serology, which remains a gold
Summary
Schistosomiasis is a snail-borne parasitic disease of great concern worldwide, occurring mainly in Africa, Asia, and to a lesser degree in South America and the Middle East [1,2]. The diagnosis of urogenital and intestinal schistosomiasis currently relies on microscopy procedures which are time-consuming, require trained operators and offer poor sensitivity, when the parasite burden is low. Among the current panel of serological techniques which are highly sensitive, the development of an immunoblotting assay using S. mansoni and S. haematobium adult worm extracts improved the performances of serological screening and proved to be relevant in both urogenital and intestinal schistosomiasis [7,8]. In endemic populations, circulating adult worm-derived antigens have been reported to be good indicators of active infection, but still appear to lack sensitivity, especially in case of low parasite burden [9,10,11]. The diagnosis of schistosomiasis currently relies on microscopic detection of schistosome eggs in stool or urine samples and serological assays. The aim of the study was to evaluate two in-house real-time Schistosoma PCRs, targeting respectively S. mansoni [Sm] and S. haematobium [Sh] in excreta, biopsies and sera as potential tools to diagnose active infections and to monitor treatment efficacy
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