EPIDEMIOLOGIC APPLICATION OF CIRCULATING ANTIGEN-DETECTION IN A RECENT SCHISTOSOMA-MANSONI FOCUS IN NORTHERN SENEGAL

Quantitative enzyme-linked immunosorbent assays (ELISAs) for the detec tion of circulating anodic antigen (CAA) and circulating cathodic anti gen (CCA) in serum and urine were applied as an epidemiologic tool in a recent, intense focus of Schistosoma mansoni in Senegal. Both CAA an d CCA in serum and CCA in urine were found in 94%, 83%, and 95%, respe ctively, of the population, of which 91% were positive on stool examin ation. Circulating antigens were also detectable in sera and urines of most egg-negative individuals. The sensitivities of the urine CCA and serum CAA ELISA were substantially higher than that of a single egg c ount, and increased with egg output. The CAA and CCA levels correlated well with egg counts and with each other. The age-related evolution o f antigen levels followed a similar pattern as egg counts, providing s upplementary evidence for a genuine reduction of worm burdens in adult s in spite of the supposed absence of acquired immunity in this recent ly exposed community. The antigen:egg ratios decreased in adults, sugg esting lower worm fecundity in children. This would be compatible with a density-dependent reduction of fecundity, but not with anti-fecundi ty immunity in adults that perhaps has not yet developed in this new f ocus.