Natural transmission of Cryptosporidium parvum between dams and calves on a dairy farm

The transmission of Crytrosporidium parvum between dams and their respectiv e calves was studied. For this purpose, fecal specimens taken from the rect um of preparturient, parturient, and postparturient dams were analyzed for C. parvum oocysts. Fecal specimens were taken from the newborn calf 4 hr af ter birth. Because the environment can be a source of contamination to the animals, specimens taken from inside and outside the barn were analyzed. Th e sucrose concentration method together with the Zielh-Nielsen acid-fast st aining method were employed to increase the chances of oocyst detection. We are reporting that at pariurition, the dams shed a higher number of oocyst s by comparison to the preparturient and postparturient periods. Neonates a cquire the infection at birth mainly because of the high number of oocysts shed by the dams at parturition. The management practice of moving calves 4 hr after birth away from the darns and the barn reduces the number of clin ical cases because they are no longer in contact with an environment that i s highly contaminated. We hypothesize that the increase in the number of oo cysts sheds by dams at parturition might be due to a depression of the T he lper 1-type of immune response during that period.