Assessment of cure by detection of circulating antigens in serum and urine, following schistosomiasis mass treatment in two villages of the Office du Niger, Mali.

ABSTRACT

Eight weeks after mass chemotherapy with 40 mg/kg praziquantel in two villages in Office du Niger (an irrigation area in Mali, endemic for both Schistosoma haematobium and Schistosoma mansoni) the circulating anodic (CAA) and cathodic (CCA) antigen detection assays were carried out on serum and urine samples. Both prior and post treatment highest prevalence was measured with the urine-CCA assay. Cure rates determined by antigen detection were almost half that of the egg counting methods. It was shown that the reduction in intensity should be preferentially assessed by the serum-CAA assay. Compared with egg detection, a single antigen detection assay gave a much better assessment of the impact of chemotherapy.

ABSTRACT

PIP Surveys conducted in different regions of Mali, to compare the circulating anodic antigen (CAA) and circulating cathodic antigen (CCA) detection assays with the classical method of parasitologic egg counting in the diagnosis of schistosomiasis, found the highest sensitivity with the urine CCA assay. The present study investigated cure rates in a mixed Schistosoma haematobium/S. mansoni endemic area by applying the CAA and CCA assays on 97 serum and urine specimens from Dogon, Mali. 8 weeks after mass treatment with 40 mg/kg of praziquantel, the cure rate was 87% according to 2 urine egg counts and 96% as determined by a single stool egg count. Both before and after treatment, the highest prevalence was again measured by the urine CCA assay. Cure rates determined by antigen detection were almost one-half that of the egg counting method. Reduction in intensity, as determined by serum CAA concentrations, was above 90% in both villages in the study area. The urine CCA assay, however, showed a reduction in intensity in one site and an increase in the other. These results suggest that the serum CAA assay should be used preferentially to assess the reduction in intensity, since serum antigen levels reflect worm burdens more directly than those in urine, given their influence by renal excretion dynamics. Timing of cure rate determination by using antigen detection should take into account local transmission patterns.