Abstract
Schistosomiasis caused by Schistosoma mansoni, one of the most neglected human parasitoses in Latin America and Africa, is routinely confirmed by microscopic visualization of eggs in stool. The main limitation of this diagnostic approach is its lack of sensitivity in detecting individual low worm burdens and consequently data on infection rates in low transmission settings are little reliable. According to the scientific literature, PCR assays are characterized by high sensitivity and specificity in detecting parasite DNA in biological samples. A simple and cost effective extraction method for DNA of Schistosoma mansoni from urine samples in combination with a conventional PCR assay was developed and applied in an endemic area. This urine based PCR system was tested for diagnostic accuracy among a population of a small village in an endemic area, comparing it to a reference test composed of three different parasitological techniques. The diagnostic parameters revealed a sensitivity of 100%, a specificity of 91.20%, positive and negative predictive values of 86.25% and 100%, respectively, and a test accuracy of 94.33%. Further statistical analysis showed a k index of 0.8806, indicating an excellent agreement between the reference test and the PCR system. Data obtained from the mouse model indicate the infection can be detected one week after cercariae penetration, opening a new perspective for early detection and patient management during this stage of the disease. The data indicate that this innovative PCR system provides a simple to handle and robust diagnostic tool for the detection of S. mansoni DNA from urine samples and a promising approach to overcome the diagnostic obstacles in low transmission settings. Furthermore the principals of this molecular technique, based on the examination of human urine samples may be useful for the diagnosis of other neglected tropical diseases that can be detected by trans-renal DNA.
Highlights
Schistosomiasis is from a global public health perspective one of the most important water-borne parasitosis and a major neglected tropical disease, with more than 200 million people infected and close to 800 million at risk [1]
The Polymerase Chain Reaction (PCR) technique applied in the urine samples identified 80 of the 194 participants as positive for schistosomiasis, indicating an infection rate of 41.24%
The results of this study clearly show the significant underestimated schistosomiasis infection rate in this setting and confirm data published in another study of our group carried out under similar conditions [10]
Summary
Schistosomiasis is from a global public health perspective one of the most important water-borne parasitosis and a major neglected tropical disease, with more than 200 million people infected and close to 800 million at risk [1]. In the specific case of Schistosoma mansoni substantial progress has been made in the control of this disease in Egypt and Latin America by reducing morbidity and prevalence, transmission continues, and the disease has spread to previously non-endemic areas [3,4,5]. Under these circumstances, characterized by low prevalence and infection intensity, the routinely used diagnostic tool, based on the detection of parasite eggs in stool, the Kato-Katz technique [6], lacks sensitivity to identify reliably positive cases [7,8,9]. All these methods require collection of blood, an inconvenience for their application at large scale [15]
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