Diagnostic challenges in male genital schistosomiasis (MGS): Preliminary real-time PCR results of a longitudinal cohort study in Malawi.
Introduction: Male genital schistosomiasis (MGS), is an under-reported manifestation of urogenital schistosomiasis (UGS), defined by schistosome eggs in seminal fluids, genitalia and their associated pathologies. At present, semen microscopy is considered as a standard technique for diagnosing active MGS infection and urine filtration with microscopy in presence of MGS symptoms serves as a convenient but error-prone diagnostic proxy of MGS. Unlike the advances made in defining a gold standard technique for diagnosis of female genital schistosomiasis (FGS), MGS remains inadequately defined. Longitudinal cohort study among fishermen along southern shoreline of Lake Malawi was conducted to investigate the current prevalence of MGS using parasitological and molecular diagnostic techniques including real-time polymerase chain reaction (PCR).
Methods: Participants (fishermen) recruited in the cohort MGS study at baseline, were interviewed with individual knowledge, attitudes and practices questionnaires, and requested to submit mid-morning urine and semen. The urine was assessed visually, with reagent (Siemens multistrix 10G)
and point-of-care circulating cathodic antigen (POC-CCA) strips before filtration through a polycarbonate membrane before microscopy to detect schistosome ova. Direct microscopy of semen submitted in a clean, transparent plastic bag was conducted to diagnose MGS before centrifugation and repeat microscopy of the sedminent. The sediment was preserved in ethanol and shipped frozen to a molecular laboratory for real-time Polymerase chain reaction analyses. Transabdominal and scrotal ultrasonography were conducted on the participants to investigate for genital pathologies. Praziquantel treatment at 40 mg / kg was offered at the end and were invited to follow-up studies after 1-, 3-, 6- and 12-months.
Results: A total of 376 participants, aged 18 to 70 years (mean ≤ 30.6 years), were recruited into the study and had questionnaire interviews. Preliminary results at baseline indicate 17.1% prevalence of UGS (n ≤ 210, mean egg count ≤ 15 per 10mL and range ≤ 0 - 137.8). 3.8% participants tested positive for POC-CCA indicating the presence of (most probably) hepato-intestinal S. mansoni infection. For MGS (S. haematobium eggs in semen), was observed in 10.7% of participants (n ≤ 112, mean ≤ 6 eggs per mL, range ≤ 0 - 30 eggs). On semen real-time PCR analyses with positive control Ct-value of 27.7, the prevalence of MGS went up to 26.6% and 75% of participants who were positive on PCR had undetectable eggs in the semen.
At 1-month follow-up study, prevalence of UGS reduced to 11.1% (n ≤ 56, mean ≤ 13.5 eggs per 10 mL). While no participant had schistomome eggs seen in semen (n ≤ 40), the prevalence of MGS on PCR was 24.2%. At 3-months follow-up, UGS prevalence rose to 11.7% (n ≤ 56, mean ≤ 15.6 eggs per 10 mL) and MGS prevalence was 8.9% and 26.1% on microscpy and PCR respective