CIRCULATING ANODIC ANTIGEN LEVELS IN 2 AREAS ENDEMIC FOR SCHISTOSOMIASIS-MANSONI INDICATE DIFFERENCES IN WORM FECUNDITY

Serum levels of the adult schistosome circulating anodic antigen (CAA) were compared in 2 populations, both living in an area with extremely high transmission levels of Schistosoma mansoni. In one focus (Maniem a, eastern Zaire) transmission has been established for several decade s, while in the other focus (Ndombo, northern Senegal) transmission st arted only recently. While parasite egg counts in the 2 populations we re virtually similar, including analogous age-related distributions, s erum levels of CAA were approximately 5 times higher in the chronicall y exposed community. This difference in antigen level was most pronoun ced in adolescents and adults. As the level of CAA is assumed to be a direct reflection of worm burden, these findings suggest higher parasi te fecundity in the recently exposed community. It is not very likely that these observations could be explained solely by differences in cl earance mechanisms caused by a variation in experience of infection. T he relationship between circulating antigen levels and egg counts was consistent for all age groups in the Maniema population, while in the Ndombo population only children showed a pattern similar to that in th e chronically exposed community.