Protection of calves with a vaccine against Cryptosporidium parvum.

Cryptosporidium parvum causes enteric infection and diarrhea in calves, other species of economically important livestock, and humans. There are no effective treatments currently licensed for this parasite, and preventive measures are difficult. In addition to direct economic losses to the cattle industry, infected calves may contaminate water supplies with oocysts and contribute to human cryptosporidiosis. We have developed a vaccine offering partial protection against C. parvum infection in calves. Nine calves received an oral preparation of lyophilized C. parvum oocysts shortly after birth, and 10 calves served as nonvaccinated controls. All calves received colostrum. At 1 wk of age, all calves were administered 10(4) viable C. parvum oocysts orally. Clinical disease and oocyst shedding were monitored daily. Mean duration of diarrhea was 4 days for control calves and 1.7 days for vaccinated calves. Mean duration of oocyst shedding was 5.3 days for control calves and 2 days for vaccinated calves. These differences were statistically significant and suggest that this vaccine has the potential to reduce diarrhea and oocyst shedding caused by C. parvum.