Diagnostic Techniques for Soil-Transmitted Helminths – Recent Advances

Abstract

Soil-transmitted helminth (STH) infections (hookworms, Trichuris, Ascaris ) and Strongyloides spp. are associated with a substantial global burden and high morbidity. Sensitive and specific methods for diagnosis of these infections are essential for mapping the burden in communities, accurate assessment of infection levels, to guide interventions and monitoring the success of STH control programs. Despite considerable progress to control STH over several decades, we are still far from identifying a fully adequate diagnostic test. Conventional microscopy-based methods such as direct Kato–Katz smear or mounts after stool centrifugation/flotation-based concentration techniques have been the mainstay of diagnosis, especially in resource-poor countries where these infections abound. However, recently, these are being adapted to closed, easy to perform, digital formats, thereby improving the sensitivity as well as applicability in a remote, resource-limited setting. The use of image analysis systems to identify and quantify helminth eggs, with potential adaptation to smartphones, is also promising. Antibody detection tests have a limited role mostly in the case of Strongyloides hyperinfection. Coproantigen detection tests have been developed and used in veterinary practice for detection of STH, but these have not been evaluated for use in humans. More sensitive molecular diagnostics, including assays developed with new bioinformatic tools and techniques such as polymerase chain reaction (PCR), quantitative PCR (qPCR) and loop-mediated amplification assay, can help in the clear and precise assessment of STH burden during elimination phase and are of immense value for diagnosis in areas with low endemicity and in travelers to endemic regions. Moreover, the molecular techniques will help detect new species that may emerge. Sample preservation and efficient DNA extraction are critical and significantly affect the efficiency of molecular diagnostic tests. In addition to the diagnosis of clinical or asymptomatic infection in humans, detection of STH eggs in environmental samples is imperative to boost STH control efforts. Overall the diagnostic performance, cost-effectiveness, ease of performance, rapidity and in-field applicability of any test should be considered when choosing from the various diagnostic assays in areas with different endemicity, in addition to striving towards the development of novel technologies and optimization of existing methods.

Comparing the anti-parasitic effect of Ivermectin versus Albendazole against intestinal nematode worms

“…Notably, in resource-constrained regions, the Kato-Katz technique is a common tool for diagnosing STHs during epidemiological surveys and monitoring treatment effectiveness studies [52] . As no worldwide criteria exist to assure the validity of this technique's results, we aimed to examine anthelminthic efficacy using additional markers associated with intestinal response to tissue-invasive developmental stages in acute-early infections.…”

Impact of ivermectin mass drug administration on burden of soil-transmitted helminths in onchocerciasis control and elimination programs, Yeki district, southwest Ethiopia

“…The next morning, the containers with stool samples were collected and placed into a zip-locked plastic bag. Stool samples were examined with the Kato-Katz technique [ 40 ], a WHO-recommended diagnostic method for identifying and quantifying STH eggs in stools [ 41 ], which consist of a single thick smear technique with a 41.7mg template that allows a standardized amount of stool to be examined and eggs to be counted [ 42 ]. The samples were examined by a qualified laboratory technician within one hour after slides’ preparation to ensure that all STH species potentially present in the preparation should be identified.…”

Clinical value of serology for the diagnosis of strongyloidiasis in travelers and migrants: A 4-year retrospective study using the Bordier IVD®Strongyloides rattiELISA assay

“…Baermann concentration and/or Harada-Mori filter paper culture were undertaken immediately after sample reception [ 17 ]. Techniques were performed by trained operators on freshly emitted samples.…”