Schistosomiasis Diagnosis Using a CAA Antigen Test

Schistosomiasis is one of most important human parasitic diseases worldwide. Pregnant women and their infants are two vulnerable population groups, particularly in sub-Saharan Africa, where - amongst other infectious agents - they are heavily exposed to infections with S. haematobium. Adoption of the recommendation and implementation by national disease control programs was however delayed in most African countries, due to the lack of safety data in humans and in the unborn babies. First results from randomized controlled trials with PZQ in pregnant women meanwhile have provided evidence for the safety of PZQ also in newborns. In Gabon, S. haematobium is the primarily prevalent Schistosoma species infection. As it is true for most of observational and interventional studies on schistosomiasis, the power of the study is weakened due to the low sensitivity of reference schistosomiasis diagnosis applied, and one might correctly assume that a considerable proportion of samples were misclassified as negative in the control groups. Therefore, diagnostic tests that are highly sensitive and specific are essential to the detection of Schistosoma infections and are urgently needed for a test-and-treat strategy to control schistosomiasis in pregnancy as well as tools to determine efficacy of new interventions tested in clinical trials. Circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) have levels correlating with the number of worms and have also been shown to clear within a few days or weeks after successful treatment. Assays measuring serum levels of these antigens (POC-CCA, UCP-LF CAA) are therefore deemed to assess drug efficacy. Based on above mentioned tools, we decided to assess the accuracy of CAA measurement to determine the Schistosoma infection in two specific conditions: A) as a diagnostic tool for S. haematobium to prepare for the future implementation of a PZQ test-and-treat strategy and B) as a diagnostic tool to measure efficacy of prazi