ANALYSIS OF WORM BURDEN VARIATION IN HUMAN SCHISTOSOMA-MANSONI INFECTIONS BY DETERMINATION OF SERUM LEVELS OF CIRCULATING ANODIC ANTIGEN AND CIRCULATING CATHODIC ANTIGEN

Serum circulating anodic antigen (CAA) and circulating cathodic antige n (CCA) concentrations, as a possible direct measure of worm burden, w ere compared with fecal egg counts in a heavily Schistosoma mansoni-in fected population from Zaire to allow differentiation between worm loa ds and worm fecundity in relation to age and intensity of infection. O f the 517 subjects, 95% excreted eggs and 97% demonstrated circulating antigens. Fecal egg counts showed an age-related pattern characterist ic for an area in which schistosomiasis is endemic with intense transm ission levels. Regression analysis showed that antigen concentrations were strongly associated with egg counts. For CAA, but not for CCA, th is relation was found to be nonlinear, which would be consistent with density-dependent fecundity or crowding, The trend was uniform for all age groups, which for this particular population indicated a genuine reduction of worm loads rather than reduced worm fecundity with age of the host.