Improving diagnosis of urogenital schistosome infection

Abstract

Schistosomiasis (commonly known as bilharzia or snail fever) is the second (to malaria) most important human parasitic disease in tropical and subtropical in regions. In Africa, Schistosoma haematobium, the causative agent of urogenital schistosomiasis, is the most prevalent species causing human disease and is responsible for most of the schistosome-related disease in the region. Diagnosis of morbidity in field settings mainly relies on the detection of hematuria (blood in the urine) and proteinuria (protein in the urine) which results from the passage of parasite eggs through the bladder wall. Ultrasound scans of the urinary tract are also used to detect morbidity but are less practical in the majority of field settings owing to the requirement of specialized equipment and trained personnel. Current diagnosis of infection relies on detecting excreted eggs and excreted or circulating parasite products. Diagnostic methods include microscopic examination of eggs in urine (currently considered the gold standard), microscopic examination of tissue biopsies, serological and reagent strip diagnosis of circulating parasite proteins detectable in blood and urine and, more recently, detection of parasite DNA in urine or vaginal lavage samples. All currently used diagnostic methods have limitations associated with them. In particular, the gold standard microscopic enumeration of eggs in urine is less sensitive in low infections and does not detect single sex or prepatent infections, which makes it particularly inaccurate in young children harboring light infections and in older individuals with chronic infections who both excrete low levels of eggs. The detection of parasite DNA in urine samples by PCR described in the article by Ibironke et al. improves on this limitation. This article reviews the method described by Ibironke et al., compares it with current methods and discusses its potential use in field settings.