TREATMENT OF EXPERIMENTAL OVINE CRYPTOSPORIDIOSIS WITH OVINE OR BOVINE HYPERIMMUNE COLOSTRUM

Ovine or bovine colostrums with different antibody titers were tested for their ability to prevent cryptosporidiosis in five groups of neona tal lambs experimentally infected with 10(6) Cryptosporidium parvum oo cysts 2 days after birth (Day 0). In a control group (Group 1), six la mbs were deprived of ewe colostrum and exclusively fed with milk repla cer. Two groups of six lambs were allowed to suckle their non-hyperimm unized (Group 2) or hyperimmunized (Group 3) dams throughout the exper iment. Two groups of seven lambs were separated from their dams at bir th before suckling and fed with non-hyperimmune (Group 4) or hyperimmu ne (Group 5) bovine colostrum; for 7 days they received 50 ml of colos trum completed by milk replacer twice a day, then they were fed with m ilk replacer exclusively. Control lambs became infected and developed clinical cryptosporidiosis with diarrhea on Days 4-9 post inoculation, oocyst shedding and mortality (2/6). In all the treated groups, the c olostrum prevented mortality and clinical cryptosporidiosis. The morta lity (5/7) observed in Group 5 was not due to cryptosporidiosis but an emia. In treated groups, specific antibodies were detected on Day 0 af ter 2 days of colostrum intake and varied little in time for IgM and I gG in spite of the parasite development, whereas they appeared later i n the control group, on Day 4 for IgM, Day 11 for IgA and Day 14 for I gG. In all groups, the response which was the most consistent was the IgA response which evolved from Days 11 to 18 in association with the decline of oocyst shedding. Our results show that whatever the serum a ntibody titers were, the specific C. parvum circulating antibodies hav e no influence on the control of cryptosporidiosis. The prophylaxis or the treatment of cryptosporidiosis require high titers of specific C. parvum antibodies in the gut lumen during a sufficiently long period.