Abstract
Human strongyloidiasis a soil-transmitted infection caused by Strongyloides stercoralis is one of the most neglected amongst the so-called Neglected Tropical Diseases (NTDs). S. stercoralis is a nematode, which is distributed worldwide; it has been estimated that it could affect millions of people, mainly in tropical and subtropical endemic regions. The difficulties of diagnosis lead to infection rates being underreported. Asymptomatic patients have chronic infections that can lead to severe hyperinfection syndrome or disseminated strongyloidiasis in immunocompromised patients. Strongyloidiasis can easily be misdiagnosed because conventional faecal-based techniques lack of sensitivity for the morphological identification of infective larvae in faeces. None of the currently used molecular methods have used urine samples as an alternative to faecal samples for diagnosing strongyloidiasis. This study was thus aimed at comparing, for the first time, the use of a new loop-mediated isothermal amplification (LAMP) molecular assay (Strong-LAMP) to traditional methods on patients' urine samples. Twenty-four urine samples were taken from patients included in a study involving two Spanish hospitals for strongyloidiasis screening using parasitological and serological tests. Strongyloides larvae were found in 11 patients' faecal samples, thereby ascertaining that they had the disease. Other patients had high antibody titres but no larvae were found in their faeces. All urine samples were analysed by PCR and Strong-LAMP assay. No amplification occurred when using PCR. Strong-LAMP led to detecting S. stercoralis DNA in urine samples from patients having previously confirmed strongyloidiasis by parasitological tests and/or a suspicion of being infected by serological ones. The Strong-LAMP assay is a useful molecular tool for research regarding strongyloidiasis in human urine samples. After further validation, the Strong-LAMP assay could also be used for complementary and effective diagnosis of strongyloidiasis in a clinical setting.
Highlights
Strongyloidiasis is an infection caused by the parasitic nematodes from the genus Strongyloides: S. stercoralis and to a lesser extent Strongyloides fuelleborni
The urine samples were analysed by polymerase chain reaction (PCR) using F3 and B3 external primers from the set of 4 primers for the loop-mediated isothermal amplification (LAMP) assay; correct PCR functioning had already been verified with S. venezuelensis DNA
More studies are needed which would involve increasing the amount of urine samples to be analysed, the present work’s results suggest that the Strong-LAMP method and those obtained in faeces [28] have demonstrated that the technique could be used as a complementary molecular tool when diagnosing strongyloidiasis
Summary
Strongyloidiasis is an infection caused by the parasitic nematodes from the genus Strongyloides: S. stercoralis and to a lesser extent Strongyloides fuelleborni. Diagnosis is undoubtedly the main problem regarding strongyloidiasis due to little knowledge being available concerning the disease, its effects in nonendemic areas, current diagnostic techniques having little sensitivity and specificity, the parasitological methods requiring specialised personnel, and centres and no gold standard for diagnosis. This means that the case definition and the possible validation of new diagnostic methods are enormously hampered [20]. The Strong-LAMP is used for the first time in human urine samples from patients attending at two hospitals in Spain and compared with parasitological and serological methods
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