Experiments were undertaken to determine whether passive immunization utilizing hyperimmune bovine colostrum (HBC) specific for Eimeria acervulina (EA)
antigens conferred protection against
coccidiosis in chickens. The HBC was produced by immunizing three pregnant, nonmilking Jersey cows with EA
antigens administered via one
intramuscular injection followed by three intramammary infusions at approximately 10, 8, 6, and 4 wk before parturition. One cow was immunized with sporozoites (SZ), the second with merozoites (MZ), and the third with recombinant merozoite
antigen (rMZ). A fourth cow, unimmunized, provided normal colostrum (NC) for control purposes. Colostral whey from each cow was tested by ELISA for antibody against SZ, MZ, and rMZ
antigens. In all immunized cows, antiparasite titers were elevated above those of the control.
Antibodies from MZ- and rMZ-immunized cows recognized both MZ and rMZ
antigen. Separate groups of 2-wk-old chickens received two oral doses of anti-SZ, -MZ, or -rMZ HBC or NC or PBS daily from 1 day before through 6 days after oral inoculation (DAI) with EA oocysts. Feces from each group were examined for oocysts. Intestines were examined for lesions 6 DAI. Histologic sections of duodenum were examined for asexual stages and gametocytes utilizing
monoclonal antibody and fluorescence microscopy. In Experiments 1 and 2, oocyst production was reduced in all HBC-treated groups, except one treated with rMZ HBC, compared with PBS- or NC-treated groups. In Experiment 2, the severity of lesions was significantly reduced in all HBC-treated groups compared with those that received NC or PBS. Significantly fewer developmental stages were found in histological sections from all chickens treated with anti-SZ and anti-rMZ HBC than from controls. Anti-SZ HBC significantly reduced the number of intracellular SZ found 24 h after their inoculation into cultures of primary chicken kidney cells. These results suggest that HBC specific for certain EA
antigens can inhibit parasite development and reduce severity of parasite-related gut lesions.