BACKGROUND: Cryptosporidium parvum is a coccidian parasite with worldwide distribution. OBJECTIVES: It is considered as one of the most important causes of diarrhea in many vertebrate species and immunocompromised human. Due to the lack of effective treatment of cryptosporidiosis, protection strategy against this species can be focused on the encourage of immune system through vaccine development. 35 METHODS: For this aim we prepared oocysts lysate as whole antigen vaccine candidate (420 μg) and immunized 3 pregnant cows 4 times every 2 weeks from 70 days to parturition. As a control group 3 unimmunized pregnant cows were used. After parturition, each calf was fed with colostrum of his dam and challenged at 12h of age with 1×107C. parvum oocysts. RESULTS: In contrast to the test group, the calves in the control group developed severe watery 40 diarrhea with excretion of oocysts from 4 days post infection. The calves in the test group, which received the hyperimmune colostrum, not only showed no clinical signs, but also had a significant reduction in oosysts excretion. CONCLUSIONS: The whole antigen prepared from oocysts of C. parvum can be considered as a suitable candidate for immunizing of pregnant cows producing hyperimmune colostrum.

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