Image: Egg of Schistosoma haematobium in a wet mount of urine concentrates, showing the characteristic terminal spine (Photo courtesy of the Centers of Disease Control and Prevention).
Urogenital schistosomiasis, which is caused by Schistosoma haematobium
, is diagnosed by finding the blood-borne flukes eggs in urine samples and simplifying sample preparation in the field before microscopy is vital for efficient and cost-effective diagnostic strategies in resource-constrained settings.
Urine filtration and light microscopy remain an important diagnostic procedure for detection of S. haematobium
infection but techniques used for concentration of eggs from urine involve either centrifugation or filtration by using specialized microporous membranes, which are relatively expensive for use in low-income countries.
Laboratory scientists the University of Cape Coast (Ghana) working with their international colleagues evaluated inexpensive and widely available paper products including paper towels, school workbook paper, and newspaper to gravity-filter urine. Urine samples from 10 patients with recently microscopically confirmed, high-intensity infection with S. haematobium
were included in this proof-of-concept study. Urine was pooled such that the same infection intensity of 60 eggs/mL was evaluated by each filtration device.
The three different paper products were rolled into a cone fitted into a funnel. Urine with the eggs was poured into the cone, which enabled gravity filtration of urine through the paper into a cup below. After filtration, scissors were used to cut off the bottom of the paper cone into which urine was poured. This paper was placed on a glass slide and examined it for ova by using conventional light microscopy.
The scientists were able to visualize S. haematobium
eggs on all five paper towel filtered samples by using conventional light microscopy. They were not able to visualize S. haematobium
eggs with either the workbook paper or newspaper products because of issues with tearing of the paper when transferring it to the microscope and the way light was refracted off of the paper.
The investigators recommend the evaluation of other low-cost paper products for filtration, diverse infection intensities, and the role of non-expert microscopists in public health and clinical settings. In addition, given the simplicity of this diagnostic platform, they envisioned portable light microscopic devices, including mobile phone microscopy, to aid in evaluation of filtered urine for S. haematobium
infection. This procedure may enable poorly equipped peripheral clinics and public health services in rural or remote communities to facilitate diagnosis of this neglected tropical disease. The study was published on June 30, 2014, in the American Journal of Tropical Medicine and Hygiene.
University of Cape Coast