Microscopic detection and genetic characterisation of schistosome eggs within cervicovaginal lavage sediments from cases of female genital schistosomiasis

Control of female genital schistosomiasis (FGS) has gained significant international attention, driven in part, as a newly appreciated underlying aetiological risk factor for HIV, HPV and cervical dysplasia. Whilst diagnosis and clinical staging of FGS typically relies upon colposcopy, alternative methods of incrimination have grown, particularly upon application of PCR diagnostic assays that detect schistosome DNA within tissue biopsy, genital (self-)swab and/or cervicovaginal lavage (CVL). With regard to the latter, we present novel evidence that microscopy alone of CVL sediments can be sufficient to incriminate FGS and CVL sediment provides an original source of (viable) schistosome eggs and miracidia for later genetic analysis. Upon a pilot examination of 55 adult women from Malawi with previously proven urogenital schistosomiasis by egg-patent urine microscopy, 25.5% (95% CI = 14.7 - 39.0) were found to have schistosome eggs within CVL, with one woman having more than 50 eggs observed. After praziquantel treatments and upon re-examination one year later, the prevalence of egg-patent CVLs reduced to 14.5% (95% CI = 6.5 - 26.7) although the same woman again presented with more than 50 observable eggs. Molecular DNA analysis by real-time PCR of extracted DNA from CVL sediments and CVL hatched miracidia (and eggs) revealed the dominance of Schistosoma haematobium within the samples, noting a fifth with Schistosoma mattheei co-infections and the singular presence of a putative S. haematobium x mattheei hybrid miracidium. Viable schistosome eggs shed from cervicovaginal surfaces likely represent a minor environmental transmission route, thus promoting secure menstrual hygiene management is needed.