Survey of Schistosomiasis in Saint Lucia: Evidence for Interruption of Transmission

Circulating Anodic Antigen (CAA): A Highly Sensitive Diagnostic Biomarker to Detect Active Schistosoma Infections—Improvement and Use during SCORE

“…From these results, it is clear that if S. mansoni infections still exist on St. Lucia, they are not present in the children who were surveyed. 38 The finding of some inconsistent low-level positive results by the various assays indicates they are likely false positives, which highlights the difficulties in setting assay thresholds with 100% accuracy when targeting maximal sensitivity of any diagnostic test.…”

Evaluation, Validation, and Recognition of the Point-of-Care Circulating Cathodic Antigen, Urine-Based Assay for Mapping Schistosoma mansoni Infections

“…In collaboration with the Ministry of Health and Wellness of the Government of St. Lucia, the Pan American Health Organization, and the Centers for Disease Control and Prevention (CDC), SCORE assisted in mapping study of all primary schools (n = 63) on St. Lucia. 24 This mapping included 16% of the 8,985 children aged between 8 and 11 years on the island and included collection of urine (n = 1487) and finger-stick blood (n = 1455) samples. Fourteen percent (n = 209) of the children providing a urine sample had a trace (n = 150) or 1+ (n = 59) POC-CCA result in the field.…”

“…Therefore, we concluded that negative and inconclusive results using those two assays meant that none of the children in the study was confirmed to have S. mansoni infection. 24 INTERPRETING TRACE-POSITIVE READINGS OF THE POC-CCA ASSAY It is clear based on the data from very low-prevalence settings that an important challenge is how to read and interpret visually faint bands, called "trace." The manufacturer's instructions stated that trace should be considered as positive, and, eventually, most of the evidence generated by LCAs and other studies led the WHO to also state that trace results should be considered positive.…”

“…However, in areas that are nearing or perhaps have achieved elimination, for example, in St. Lucia and the areas in Egypt where the aforementioned studies were conducted and control interventions have been going on for many decades, it appears that trace POC-CCA readings are very likely to all be false positives. 24,29,30 In deciding whether POC-CCA trace readings should be interpreted as false or true positives, we propose that both the control history and current prevalence of the location should be considered. As indicated earlier, the three villages in the Egyptian studies had prevalence levels of 1.2%, 0.0%, and 0.9% by the KK assay based on more than 2,000 children tested.…”

“…In the same survey, the POC-CCA prevalence in these villages, testing the same children, was 9.8%, 10.8%, and 7.6%, respectively, 27 and almost 90% of those read as positive by POC-CCA were trace or 1+ readings. Furthermore, the mapping in St. Lucia 24 was performed more than three decades after extensive interventions were applied across the country, and St. Lucia had undergone widespread development with much of the country moving from an agricultural-based to a tourism-based economy. 31,32 It seems likely that any schistosomiasis transmission dynamics encountered in St. Lucia and the three study villages in Egypt would differ considerably from those taking place in Burundi and Rwanda, each of which had undergone selective area MDA with PZQ for only 6 years at the time of the mapping surveys.…”