Schistosomiasis: an epidemiological update on Brazil's southernmost low endemic area in Esteio

Abstract

Introduction: Brazil's southernmost state, Rio Grande do Sul (RGS), was considered schistosomiasis-free until 1998 when a low endemic focus was identified in Esteio, a city located next to the capital of RGS. In the last two decades, the control interventions applied in the region have been apparently successful, and the absence of new cases indicated the possibility of interrupted schistosomiasis transmission. The objective of this study was to update the clinical and epidemiological data of schistosomiasis in Esteio. Methods: We reviewed all 28 individuals diagnosed with the infection since 1997 and a survey was applied to a group of 29 school-aged children residing in Vila Pedreira, one of the most affected neighborhoods. Results: No eggs were detected in fecal samples using the Helmintex method, and all samples were negative for serum antibodies on examination by the western blot technique using the Schistosoma mansoni microsomal antigen (MAMA-WB). In contrast, 23 individuals (79%) tested positive for the cathodic circulating antigen with the point-of-care immunochromatographic test (POC-CCA) on urine samples. Of the 28 formerly infected individuals, only eight were located, of which four tested positive, and four tested negative for serum antibodies using the MAMA-WB technique. Conclusions: Current adverse conditions for S. mansoni transmission in Esteio and the absence of a confirmed diagnosis suggests that there is (i) a lack of specificity of the POC-CCA test in low endemic settings, and (ii) a high probability that interruption of schistosomiasis has been achieved in Esteio.

Assessment of the accuracy of 11 different diagnostic tests for the detection of Schistosomiasis mansoni in individuals from a Brazilian area of low endemicity using latent class analysis

“…As previously mentioned, the performance of POC-CCA may vary according to the schistosomiasis prevalence and intensity of infection. Besides this, the test is less accurate among people with light infections and in low endemicity areas ( Viana et al, 2019 ; da Ramírez et al, 2020 ) and may present false-positive results in non-endemic areas ( Graeff-Teixeira et al, 2021 ). The outcome of POC-CCA from Eco Diagnóstica can also be influenced by the batch used ( Viana et al, 2019 ).…”

Reliability of point-of-care circulating cathodic antigen assay for diagnosing schistosomiasis mansoni in urine samples from an endemic area of Brazil after one year of storage at -20 degrees Celsius

“…These POC-ECO quality assurance and quality control issues reinforce previous concerns with Schisto POC-CCA ® from Rapid Medical Diagnostics (POC-CCA) both in freshly-collected 4,26 and stored urine 3,5 . Moreover, results from earlier studies based on a discontinued version of POC-CCA requiring one drop of urine and one drop of buffer [16][17][18][27][28][29][30][31][32] may not be comparable with those based on the new version of POC-CCA requiring two drops of urine and no buffer 3,4,24,33-35 .…”

Challenges to Schistosomiasis Control Program in Brazil: setbacks in the control program and critical analysis of the disease notification

“…However, reported outbreaks were not caused by local transmission but rather by infected individuals migrating from highly endemic states in southeastern or northeastern Brazil 25 . This migration risk extends beyond Rondônia, as evidenced by reports of focal transmission in Rio Grande do Sul 26 . These cases highlight the importance of continuous schistosomiasis monitoring.…”