A factor derived from adult rat and cow small intestine reduces Cryptosporidium parvum infection in infant rats

Cryptosporidium parvum is an intracellular protozoan parasite of the mammal ian intestine. In rats, C. parvum infection is age related; infants are sus ceptible, whereas adults are resistant. The transition from susceptibility to resistance usually takes place around the age of weaning. In the present study, infant rats were orally inoculated with a preparation of intestinal scrapings taken from adult rats or cows. Infant rats received the scraping s daily from 3 to 14 days of age, were inoculated with C. parvum oocysts at 9 days of age, and killed at 15 days of age. Fecal samples and intestinal tissues were examined for the presence of C. parvum. Significantly fewer ra ts were infected in the groups that received intestinal scrapings compared with controls. In addition, infected rats in the treatment groups shed sign ificantly fewer oocysts than those in the control group. Scrapings from the intestinal mucosa of adult cows were also able to protect infant rats from infection, whereas scrapings from intestines of calves were not protective . In sum, these data indicate the presence of a factor in the intestines of adult rats and cows that can transfer protection against C. parvum infecti on to susceptible infant rats.