Comparison of the circulating anodic antigen detection assay and urine filtration to diagnose Schistosoma haematobium infections in Mali.

The applicability of a circulating Schistosoma antigen detection assay for determining rates of infection and efficacy of chemotherapy was evaluated in Mali. Urine egg counts were compared to circulating anodic antigen enzyme-linked immunosorbent assay (CAA-ELISA) titres in serum, before and 6 weeks after treatment with a single dose of praziquantel (40 mg/kg), in 2 villages in Dogon Country, an area endemic for S. haematobium, the predominant schistosome infection in Mali. In Kassa, a village with a moderate prevalence of infection, the serological prevalence (48%) was significantly higher than the parasitological prevalence (31%). In Boro, a village with high parasitological prevalence (76%), no difference was observed between the results of both methods (prevalence by CAA-ELISA was 75%). Cure rates estimated by CAA-ELISA were lower than those determined parasitologically, suggesting that cure rates are overestimated by egg counting. The sensitivity of the CAA-ELISA was 78%. In both villages, before treatment, a positive correlation was found between the number of eggs in urine and serum CAA titres. It is concluded that, although further simplification and improvement of the sensitivity of the assay is needed, in its present ELISA format the antigen detection assay is useful for monitoring sentinel populations. Furthermore, the serum CAA assay performed adequately in a public health laboratory within an endemic country.

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.

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.

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.

Circulating anodic and cathodic antigen in serum and urine of mixed Schistosoma haematobium and S. mansoni infections in Office du Niger, Mali.

In Office du Niger, an area endemic for both Schistosoma haematobium and S. mansoni in Mali, circulating anodic (CAA) and cathodic (CCA) antigen detection assays were performed on pretreatment serum and urine samples from two villages, Rigandé and Siguivoucé, and compared with egg counting methods. The highest prevalence was obtained with the urine-CCA assay which also had the highest sensitivity to S. haematobium, S. mansoni or mixed infection. A single urine-CCA assay was as sensitive as repeated egg counts (one stool+two urine examinations per individual). When the different assays were tested in parallel, several combinations including assays on serum were found to be highly sensitive. As urine sampling is widely accepted, urine assays will be used for further monitoring these villages one and two years after chemotherapy.