Diagnosis of Schistosoma mansoni infections: what are the choices in Brazilian low-endemic areas?

Abstract

The population of Brazil is currently characterised by many individuals harbouring low-intensity Schistosoma mansoni infections. The Kato-Katz technique is the diagnostic method recommended by the World Health Organization (WHO) to assess these infections, but this method is not sensitive enough in the context of low egg excretion. In this regard, potential alternatives are being employed to overcome the limits of the Kato-Katz technique. In the present review, we evaluated the performance of parasitological and immunological approaches adopted in Brazilian areas. Currently, the diagnostic choices involve a combination of strategies, including the utilisation of antibody methods to screen individuals and then subsequent confirmation of positive cases by intensive parasitological investigations.

The use of the circulating cathodic antigen (CCA) urine cassette assay for the diagnosis and assessment of cure of Schistosoma mansoni infections in an endemic area of the Amazon region

“…Even with a 100% sensitivity for up to 1.3 eggs per gram (EPG) loads 15 , its application on a large scale presented some difficulties; thus, many aspects of the HTX method were optimized, aiming to make it more efficient 16 . The HTX application confirmed this method as a high sensitivity diagnostic tool in endemic areas 14 , 17 , 18 .…”

“…The WHO and the Department of Control of Neglected Tropical Diseases in 2015 suggested the use of the POC-CCA test in endemic countries, along with the KK method, for monitoring and evaluation of control programs, whose goal is the elimination of schistosomiasis as a public health problem 2 . A published review 18 on the use of KK as an RS to evaluate the performance of the POC-CCA test for the diagnosis of S. mansoni infections showed that most of the studies were conducted in Africa. To date, ten studies on POC-CCA performance for the diagnosis of intestinal schistosomiasis have been conducted in Brazil.…”

“…When the POC-CCA test was compared with the KK method, it was reported that a single urine test showed a sensitivity equivalent to that of six 20 or nine KK slides 21 . However, recent studies on the performance of POC-CCA also showed controversial results, with reduced accuracy and elevated false negative or false positive rates, particularly in low prevalence areas 22 , 14 , 17 , 18 .…”

Analysis and spatial distribution of schistosomiasis mansoni in a historically endemic area of northeastern Brazil

“…It is known that in a low prevalence area the disease persists, due to conditions linked to the environment, the vector and the social conditions of individuals in the area [20,21,22]. Nevertheless, it is also worth highlighting the weight of the ineffectiveness of the diagnosis by Kato-Katz in these areas of low endemicity [23,24,25], which allows individuals with the parasite to continue eliminating eggs in the environment and contaminating water collections with the presence of the intermediate hosts of S. mansoni. It is imperative, therefore, that municipalities carry out the actions of the PCE effectively, minimising as much as possible the proportion of non-treatment of the population due to refusal and/or absence, in addition to an effective assessment by health authorities of how activities are being developed with a view to correcting any procedural problems and maximising efforts to eliminate schistosomiasis in the country.…”

A historical review of the techniques of recovery of parasites for their detection in human stools

“…Biotechnology techniques are essential tools in certain situations 49,50 ; however, the use of molecular or immunological methods to detect parasites in fecal samples may not meet the economic and operational requirements of a laboratory, especially in regions with limited resources 17,25,26,[50][51][52] . Large reference centers can adopt these more sophisticated methods for research and differentiation between morphologically similar species 49,51 .…”