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

Vanessa Silva-Moraes,Ana Lucia Teles Rabello,Donald A Harn,Rafaella Fortini Queiroz E Grenfell,Lisa M Shollenberger,Paulo Marcos Zech Coelho,Liliane Maria Vidal Siqueira,William Castro-Borges

doi:10.1590/0074-02760180478

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.

Highlights

Schistosomiasis is one of seventeen neglected tropical diseases (NTDs) listed by the World Health Organization (WHO), and this disease presents a substantial public health and economic burden and is considered a disease of poverty
An estimated 779 million people are at risk of infection, and approximately 252 million people are currently infected.[1,2] The Global Health Estimates of 2015 attributed 3.51 million disabilityadjusted life years (DALYs) and 10.1 million deaths in 2016 to schistosomiasis, which is a mortality figure that has been challenged as a gross underestimate.[3,4] In the Americas, the only known species of parasite that is associated with intestinal schistosomiasis and continues to be endemic in parts of Brazil, Venezuela, and the Caribbean is Schistosoma mansoni.[5]
Kato-Katz technique (K-K), possesses poor sensitivity for low-intensity infections and cannot be currently considered the gold standard. [16,17] Improvements in the diagnostic field are strongly supported by control programs in Brazil, which is a lowendemic country where PZQ mass drug administration (MDA) is only indicated in localities with egg-positivity above 25% and the main control strategy focuses on strengthening diagnoses and treatment of infected individuals at the primary care level.[5,18,19,20]

Summary

Introduction

Schistosomiasis is one of seventeen neglected tropical diseases (NTDs) listed by the World Health Organization (WHO), and this disease presents a substantial public health and economic burden and is considered a disease of poverty. The first is improvement of parasitological methods (increased number of samples or K-K slides and addition of other more sensitive egg-based assays), the second is antibody-based detection as an auxiliary tool to parasitological investigations (acute diagnostic and preliminary screening in endemic areas), and the third is antigenbased RDT POC-CCA® as a possible candidate to be part of the control.

Results

Conclusion