EXPERIMENTAL SCHISTOSOMA-BOVIS INFECTION IN GOATS - CIRCULATING ANTIGEN AND ANTIBODY-RESPONSES TO EGG AND ADULT WORM ANTIGENS DURING INFECTION AND FOLLOWING TREATMENT WITH PRAZIQUANTEL

Circulating antigen levels and antibody responses in Schistosoma bovis -infected West African Dwarf goats were evaluated during infection and following treatment with praziquantel (60 mg/kg) 13 weeks post-infect ion. One day, 1 week and 4 weeks post-treatment, subgroups of goats we re sacrificed and perfused for worm recovery. For comparison, parasite -free control animals were included. Blood and faecal samples were col lected biweekly. Two gut-associated schistosome antigens, circulating cathodic and circulating anodic antigen (CCA and CAA) and 3 specific a ntibody responses (total Ig, IgG and IgM) were measured. For specific antibody detection, crude S. bovis adult worm and egg homogenates were used. The level of CCA in the infected groups was significantly eleva ted from the time of onset of egg excretion onwards. However, followin g treatment, the CCA titres dropped to control levels within 1 week po st-treatment. Strong positive correlations were found between CCA leve ls and worm counts and faecal egg counts during peak egg excretion. Th e correlations of CAA and specific antibody titres to egg and worm cou nts were poor. The antibody responses were all significantly elevated in the infected goats during patency, but only marginally affected by the treatment. Hence, CCA proved to be superior by correlating strongl y to the level of infection and by being a sensitive indicator of the effect of treatment.