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 los
ses to the cattle industry, infected calves may contaminate water supp
lies with oocysts and contribute to human cryptosporidiosis. We have d
eveloped a vaccine offering partial protection against C. parvum infec
tion in calves. Nine calves received an oral preparation of lyophilize
d C. parvum oocysts shortly after birth, and 10 calves served as nonva
ccinated controls. All calves received colostrum. At 1 wk of age, all
calves were administered 10(4) viable C. parvum oocysts orally. Clinic
al disease and oocyst shedding were monitored daily. Mean duration of
diarrhea was 4 days for control calves and 1.7 days for vaccinated cal
ves. 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.