EVALUATION OF SCHISTOSOMA-BOVIS ADULT WORM EXTRACT FOR VACCINATION OF CALVES

Six calves were immunized with adult worm extract of Schistosoma bovis emulsified in Freund's adjuvant. The immune response was monitored by agar-gel immunodiffusion. Precipitin lines were observed when sera from immunized calves were tested against adult worm antigen, but no lines were observed with sera from control calves. The immunized calves together with six control calves were each challenged with 20 000 cercariae of Schistosoma bovis administered percutaneously to the shaved tail. There was no significant difference between the immunized and the control groups as judged by fecal and tissue egg counts, worm recovery and hematological parameters (including packed cell volume and hemoglobin concentration). This indicates failure of S. bovis adult worm extract to induce resistance against S. bovis challenge. Hence, the antibody response detected in the AGID test seemed to have no association with protection.