Paromomycin is effective as prophylaxis for cryptosporidiosis in dairy calves.

Of 16 experimentally infected neonatal dairy calves, 12 were fed paromomycin twice daily in their milk for 11 consecutive days beginning 1 day before oral inoculation with 1.5-2.0 x 10(6) oocysts of Cryptosporidium parvum. Four calves each in groups A, B, C, and D received total daily doses of 100, 50, 25, and 0 mg of paromomycin per kilogram of body weight, respectively. From birth until 28 days of age feces from each calf were examined for diarrhea, and oocysts were enumerated, rectal temperature was recorded, and weight gain was determined. Total days of diarrhea, severity of diarrhea, the total number of days oocysts were shed, and the number of oocysts shed were significantly less in group A than in the unmedicated group D. The severity of diarrhea was also significantly less in groups B and C than in group D. Oocysts were not detected in feces from calves in group A. Except for 1 calf, oocysts were not detected from calves in groups B and C during the first week the drug was administered and those calves that shed oocysts began shedding at or near the end of paromomycin administration or more than 1 wk after treatment ended. Frequency of fever and weight gains did not vary significantly between the unmedicated and medicated groups except for group C, calves of which gained significantly less weight than those in all other groups.