BSP Spring Meeting 2019
Schedule : Back to Dr Lisette van Lieshout

Early diagnosis of acute schistosomiasis by detection of the circulating antigen CAA in serum and urine in a cluster cohort of 34 Belgium travellers exposed in South Africa.

Mon15  Apr04:45pm(15 mins)
Where:
Renold C9
Dr Lisette van Lieshout

Authors

L Van Lieshout2; P T Hoekstra2; M Van Esbroeck1; L Cnops1; J De Vries2; P L Corstjens2; G J Van Dam2; J Clerinx1
1 Institute of Tropical Medicine Antwerp, Belgium;  2 Leiden University Medical Centre, Netherlands

Discussion

In non-endemic settings, travellers or migrants are generally diagnosed with schistosomiasis by detection of specific antibodies in serum. Although serology is sensitive and specific, it cannot distinguish active from past infection while it may take several weeks or even months for seroconversion to occur. A more accurate diagnostic tool is detection of adult worm circulating antigen (i.e. CAA) in serum or urine, which reflects the presence of viable parasites. Here we explored three diagnostics tests in a cluster of 34 Belgian travellers who were recently and simultaneously exposed to Schistosoma during a short travel to South Africa. These cases were seen at the Institute of Tropical Medicine, Antwerp, Belgium (ITM), during the early symptomatic phase 4-5 weeks after exposure, at week 7-8 when treatment with praziquantel was given and at week 12-14. While no eggs were seen in microscopic examination of stool and urine samples, all 34 travellers were confirmed to have acquired a Schistosoma infection based on the 100% cumulative positive outcome of the PCR test for the detection of the Dra1 sequence of the S. haematobium complex in serum.(1) While the serum Dra1 PCR was able to diagnose infection at a much earlier stage than any of the other applied ITM standard diagnostic tests, including serology, the Dra1 PCR was also found to be similarly unsuitable for short-term monitoring the effect of drug treatment.(1) Stored urine (4 mL) and serum (0.5 mL) samples of this cluster were retrospectively examined for CAA concentrations by utilizing the highly specific and ultrasensitive quantitative Schistosoma Up-Converting Phosphor Lateral Flow CAA assay (UCP-LF CAA). Additional antibody testing was done by performing two in-house serology assays which are routinely applied at the Leiden University Medical Center for the diagnosis of imported schistosomiasis, i.e. an immunofluorescence assay (IFA) detecting IgM directed against adult S. mansoni worm gut antigen and an enzyme immuno assay (EIA) detecting IgG directed against S. mansoni soluble egg antigen (SEA). Urine and serum CAA concentrations and the outcome of IgM-IFA and IgG-EIA were compared with data of the Dra1 PCR and serology previously performed at ITM. Findings showed detectable CAA levels as early as 4-5 weeks after exposure in 27% (8/30) of the urine samples and 91% (30/33) of the serum samples, with a final CAA detection rate in serum of 97% (33/34) before praziquantel treatment was given. Following treatment with the anthelminthic drug CAA levels dropped significantly. No CAA was detected in 30 urine samples and 34 serum samples, except one serum showing a CAA concentration just above the cut-off level, all tested 6-8 weeks after treatment. IgM-IFA and IgG-EIA showed higher numbers of positive cases than the previously used serology tests, with a final detection rate of 82% (28/34), but, as expected b

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