Circulating Schistosoma DNA in seropositive patients: A twostep diagnostic approach to rule-out acute and active chronic schistosomiasis in low transmission settings

Abstract

Background: Since its discovery in 1850 by Theodor Bilharz at Kasr Al-Ainy hospital, Cairo, Egypt, schistosomiasis continues to be a significant health challenge with a wide spectrum of chronic sequelae. There is no reliable single gold standard conventional method (microscopy or serology) for communities with low intensity and low transmission settings.Objectives: To evaluate a two-step immunomolecular diagnostic approach to rule-out recent Schistosoma re-infection in patients with characteristic pathological radiological features of chronic schistosomiasis.Subjects and Methods: Single serum samples were collected from patients from Kafr El Sheikh, Egypt. Selection of patients was based on microscopic absence of Schistosoma spp. eggs in either stool or urine samples; abstinence from treatment by Praziquantel in the last 2 months; and clinical and radiological diagnosis of pathological features of chronic schistosomiasis. All serum samples were serologically examined using indirect hemagglutination test (IHAT) for identification of anti-Schistosoma antibodies. Serum samples from 100 seropositive patients using IHAT were tested by multiplex PCR (mPCR) for detection of species-specific cell-free circulating Schistosoma DNA.Results: None of the seropositive serum samples were positive by PCR targeting Schistosoma speciesspecific gene. Patients who were farmers and/or who had received Praziquantel treatment were associated with Schistosoma seropositivity with statistical significance.Conclusion: A two-step immunomolecular diagnostic approach, using a single serum sample, can rule-out acute or active chronic schistosomiasis in patients that have characteristic pathological and radiological features of chronic schistosomiasis. Also, the two-step approach avoids over-treatment and development of drug resistance to Praziquantel, the only effective broad anti-Schistosoma medicine.