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Effect of nitazoxanide on cryptosporidiosis in experimentally infected neonatal dairy calves

T. L. Ollivett^*, D. V. Nydam^,1, D. D. Bowman, J. A. Zambriski, M. L. Bellosa, T. C. Linden and T. J. Divers^*

^* Department of Clinical Sciences, Box 20, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
Department of Population Medicine and Diagnostic Sciences, Box 29, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853
Department of Microbiology and Immunology, C5-181 VMC, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853

¹ Corresponding author: dvn2{at}cornell.edu

Cryptosporidium is a zoonotic protozoan that is most often diagnosed in association with diarrhea in 1- to 3-wk-old dairy calves. There are neither consistently effective nor approved antimicrobial drugs for treatment in animals. The objective of this study was to test nitazoxanide (NTZ) as a treatment for cryptosporidiosis in experimentally infected dairy calves. A randomized, controlled, and blinded trial was performed using Holstein bull calves obtained from a large commercial dairy. All births were attended by study personnel and calves were fed 4 L of heat-treated colostrum within 1 h of birth. Calves were randomly assigned to treatment or placebo group and maintained for a 32-feeding (16 d) study period. Twenty-three calves were enrolled with 3 lost to follow up. Thirteen calves were assigned to the treatment group and 7 calves to the placebo group. All calves were inoculated with 1 x 10⁶ viable Cryptosporidium parvum oocysts at feeding 3. Treatment was a commercially available NTZ product and the placebo was the carrier of the same product. Nitazoxanide was administered at 1.5 g twice per day for 5 d. Nitazoxanide or placebo treatment began after feeding 10 and when the fecal score was greater than 1 out of 3. Outcome measurements included twice-daily fecal and health scores and a once-daily oocyst count by an immunofluorescent antibody assay. Data were analyzed by nonparametric and time-to-event methods. Measures of passive transfer of antibodies, initial body weight, and onset of oocyst shedding were not different between treatment and control calves. Eighty-five percent of the NTZ-treated calves stopped shedding oocysts by the end of the observation period whereas only 15% of the placebo group stopped shedding. The median number of feedings with a fecal score equal to 3 was 2 in the NTZ group while it was 6 in the placebo group. Calves receiving NTZ were 0.13 times as likely to have severe and sustained diarrhea than control calves (95% confidence interval, 0.02–0.98). Treating calves with NTZ reduced the duration of oocyst shedding and improved fecal consistency.

Key Words: nitazoxanide • cryptosporidiosis • diarrhea • dairy calf