How can schistosome circulating antigen assays be best applied for diagnosing male genital schistosomiasis (MGS): an appraisal using exemplar MGS cases from a longitudinal cohort study among fishermen on the south shoreline of Lake Malawi

Abstract

We provide an update on diagnostic methods for the detection of urogenital schistosomiasis (UGS) in men and highlight that satisfactory urine-antigen diagnostics for UGS lag much behind that for intestinal schistosomiasis, where application of a urine-based point-of-care strip assay, the circulating cathodic antigen (CCA) test, is now advocated. Making specific reference to male genital schistosomiasis (MGS), we place greater emphasis on parasitological detection methods and clinical assessment of internal genitalia with ultrasonography. Unlike the advances made in defining a clinical standard protocol for female genital schistosomiasis, MGS remains inadequately defined. Whilst urine filtration with microscopic examination for ova of Schistosoma haematobium is a convenient but error-prone proxy of MGS, we describe a novel low-cost sampling and direct visualization method for the enumeration of ova in semen. Using exemplar clinical cases of MGS from our longitudinal cohort study among fishermen along the shoreline of Lake Malawi, the portfolio of diagnostic needs is appraised including: the use of symptomatology questionnaires, urine analysis (egg count and CCA measurement), semen analysis (egg count, circulating anodic antigen measurement and real-time polymerase chain reaction analysis) alongside clinical assessment with portable ultrasonography.

An outbreak of intestinal schistosomiasis, alongside increasing urogenital schistosomiasis prevalence, in primary school children on the shoreline of Lake Malawi, Mangochi District, Malawi

“…To respond to this outbreak of intestinal schistosomiasis, we propose that current MDA efforts should be intensi ed, adopting biannual treatment cycles in schools, which has been successfully implemented elsewhere [18], alongside expanded access to praziquantel for all community members with intestinal schistosomiasis, in need of regular treatment throughout the year [19]. From recent surveys of adult shermen who have urogenital schistosomiasis, making speci c reference to male genital schistosomiasis, co-infection with S. mansoni has been noted alongside re-infections within a calendar year [20,21]. To augment MDA and communityaccess to praziquantel, it is important to strengthen health education and outreach with suitable water, sanitation and hygiene (WASH) interventions [20,22], better appropriate to this lakeshore setting, noting that even focal application of molluscicides is inappropriate [17], given this lake's global importance in biodiversity.…”

An outbreak of intestinal schistosomiasis, alongside increasing urogenital schistosomiasis prevalence, in primary school children on the shoreline of Lake Malawi, Mangochi District, Malawi

“…To respond to this outbreak of intestinal schistosomiasis, we propose that current MDA efforts should be intensi ed, adopting biannual treatment cycles in schools, which has been successfully implemented elsewhere [18], alongside expanded access to praziquantel for all community members with intestinal schistosomiasis, in need of regular treatment throughout the year [19]. From recent surveys of adult shermen who have urogenital schistosomiasis, making speci c reference to male genital schistosomiasis, co-infection with S. mansoni has been noted alongside re-infections within a calendar year [20,21]. To augment MDA and communityaccess to praziquantel, it is important to strengthen health education and outreach with suitable WASH interventions [20,22], better appropriate to this lakeshore setting, noting that even focal application of molluscicides is inappropriate [17], given this lake's global importance in biodiversity.…”

Future schistosome hybridizations: Will all Schistosoma haematobium hybrids please stand-up!

“…Egg-patent S. mansoni was also noted in several children's stools as well as ectopic excretion in children's urine, with the general prevalence of intestinal schistosomiasis increasing (more than 50% by urine-CCA testing), enabling coinfections to surge [15,19]. Inspection of other demographic groups upon general surveillance of male genital schistosomiasis in fishermen, a urine egg-patent prevalence of S. haematobium (with typical egg morphology) was 17.1% (95% CI 4.8-22.2) although atypical S. haematobium eggs or S. mansoni eggs in urine were not found [20]. Upon real-time PCR analysis of semen with a genus-specific Schistosoma DNA probe, infection prevalence was much higher at 26.5% (95% CI 18.4-34.6), and, upon using urine-CCA tests, prevalence of intestinal schistosomiasis was 3.8% (95% CI 3.1-4.5) [19], indicative of coinfection in other community members.…”

“…mattheei?) which has not yet been subjected to molecular analyses, although a S. mattheei infection has been detected locally in B. globosus by molecular methods [20].…”

“…To highlight, in outline, the real epidemiological implications of these knowledge gaps in the detection and transmission of hybrids, an epidemiological postulate is provided in Fig 2, as based upon available survey information from Malawi [15,19,20]. Our inability to identify the presence and then tally the intensity of hybrid schistosome infections across a community severely hampers our appraisal of their epidemiological importance [10].…”