THE RELATIONSHIP BETWEEN WORM BURDEN AND LEVELS OF A CIRCULATING ANTIGEN (CAA) OF 5 SPECIES OF SCHISTOSOMA IN MICE

This study examines the ability of an assay which measures the amount of a schistosome specific antigen (CAA) in the host circulation to rel iably reflect relative worm burden. Mice were infected with 5 species of schistosome with a range of infection dose, The levels of serum CAA increased during schistosome maturation. In all species tested CAA le vels correlated well with adult worm burden once the parasites achieve d sexual maturity and remained relatively stable during the establishm ent of egg production. The amount of CAA produced varied between speci es but within each species CAA levels were proportional to worm number s: no density-dependent effects on CAA levels were observed even when mice carried worm burdens that were very large relative to host size. T-cell deprivation of the host had no effect on the CAA/worm burden re lationship in either Schistosoma mansoni or S. haematobium infections and the CAA equilibrium was unaltered in intact mice when reduction of worm fecundity occurred. These data support the use of the CAA as an accurate and robust estimate of relative schistosome burden in man.