Diagnosis of schistosomiasis mansoni: an evaluation of existing methods and research towards single worm pair detection

Abstract

The inadequacy of current diagnostics for the detection of low worm burdens in humans means that schistosomiasis mansoni is more widespread than previously acknowledged. With the inception of mass drug treatment programmes aimed at disease elimination and the advent of human vaccine trials, the need for more sensitive diagnostics is evident. In this review, we evaluate the merits and limitations of the principal diagnostic methods, namely detection of eggs in faeces; anti-schistosome antibodies in serum; parasite-derived proteins and glycans in serum or urine; parasite DNA in blood, faeces or urine. Only in the baboon model, where actual worm burden is determined by portal perfusion, have faecal smear and circulating antigen methods been calibrated, and shown to have thresholds of detection of 10-19 worm pairs. There is scope for improvement in all the four methods of detection, e.g. the identification of single targets for host antibodies to improve the specificity of enzyme linked immunosorbent assay. Despite recent advances in the definition of the schistosome secretome, there have been no comprehensive biomarker investigations of parasite products in the urine of infected patients. Certainly, the admirable goal of eliminating schistosomiasis will not be achieved unless individuals with low worm burdens can be diagnosed.

Artemether and Praziquantel: Origin, Mode of Action, Impact, and Suggested Application for Effective Control of Human Schistosomiasis

“…Although the field trials mentioned here support combination therapy, testing in conjunction with more sensitive and quantitative diagnostic tools will be needed to take us closer to the goal of applying ART/PZQ therapy for schistosomiasis elimination in non-malarious areas. Indeed, such diagnostic assays [91,92,93] have already shown that the extent of schistosome infection has been greatly underestimated, due to the diagnostic deficit of stool examination and urine filtration which are still commonly used in the endemic areas [94].…”

NTD Diagnostics for Disease Elimination: A Review

“…A number of papers reviewed the available diagnostic approaches for schistosomiasis, finding room for improvement with each [95][96][97][98][99][100][101]. Subsequently, the emerging consensus is for a stratified approach, by which difference test combinations are deployed for different use cases and tailored to the exigencies of national programmes [96,[102][103][104][105][106].…”

A library of cell-surface and secreted proteins fromSchistosoma mansoniidentifies early serological markers of infection

“…Mass administration of praziquantel to schoolchildren has been the mainstay of control programmes against schistosomiasis and this has proved relatively successful in reducing parasite burdens and contributing to elimination from some areas. Continued surveillance and early detection of new cases remains critical to avoid any risk of resurgence; however, the commonly used Kato-Katz method is not sensitive enough to detect low levels of infection, resulting in the underestimation of the number of cases [9]. Detection of parasite-derived glycans such as the circulating anodic antigen (CAA) in the urine or serum of patients by lateral-flow test is currently considered the most sensitive point-of-care assay for the detection of current Schistosoma infections as reactivity disappears rapidly following praziquantel treatment.…”

“…Diagnosis of S. mansoni infections and subsequent decisions on mass drug administration mainly rely on observing parasite eggs in the stools of patients: the Kato-Katz test. Although this method can detect current infections, it is not sufficiently sensitive to diagnose low levels of infection present in areas of low-endemicity, or in recentlytreated populations [8,9]. In these instances, the direct detection of parasite antigens such as the circulating anodic antigen (CAA) in patients' sera is a more sensitive method [10].…”