Protection of calves against cryptosporidiosis with immune bovine colostrum induced by a Cryptosporidium parvum recombinant protein

摘要

Late gestation Holstein cows with low titres of antibody to the p23 antigen of Cryptosporidium parvum were immunized 3 times with 300μg affinity purified C. parvum recombinant protein (rC7) (immune cows, n=14), or left unimmunized (control cows, n=9). Colostrum was obtained from each cow and partitioned into identical aliquots of pooled immune colostrum or pooled control colostrum. 12 calves obtained at birth from another herd received either immune or control colostrum within the first 2 h, and again at 12 and 24 h of age. A total of 6 litres was given to each calf. Each calf was challenged orally with 107 C. parvum oocysts at 12 h of age and monitored for signs of cryptosporidiosis. All 6 calves administered pooled control colostrum developed severe diarrhoea (mean total faecal volume over 11 days = 8447 ± 5600 ml) and shed an average of 1.87 ± 1.66 X 1012 C. parvum oocysts; one died. None of the 6 calves administered pooled immune colostrum developed diarrhoea (mean total faecal volume = 740± 750 ml, p < 0.05), and they shed significantly fewer oocysts (3.05 ± 2.26 X 109, p < 0.05). The absence of diarrhoea and the 99.8% reduction in oocyst excretion indicates that immune bovine colostrum induced by immunization with C. parvum recombinant protein rC7 provides substantial protection against cryptosporidiosis in neonatal calves.