Research Summary - 2
Efficacy of oral immunization with Cryptosporidium parvum in a colostrum-deprived neonatal calf challenge model
| Date/Time: |
8/28/2026
14:00
|
| Author: |
Mark Welter |
| Clinic: |
Oragen Technologies |
| City, State, ZIP: |
Ames, IA 50010 |
D.P. Carter, DVM
;
M.W. Welter, BS, MA
;
1Immunology for Veterinary Practitioners, Ames, IA, 50010
2Oragen Technologies, Urbandale, IA, 50322
Introduction:
Cryptosporidium parvum is a major cause of diarrhea in neonatal dairy calves, diagnosed by PCR in 45.1% of diarrhea fecal samples, TVMDL, Rodriguez, (2024). “Virtually all calves on all farms become infected with C. parvum”, Wyatt, Riggs, and Fayer (2010). Conventional colostrum does not contain protective levels of antibodies against C. parvum, and therapeutic agents with efficacy for C. parvum are lacking. The objective of this study was to determine the efficacy of an inactivated C. parvum preparation as an oral immunogen in a colostrum- deprived calf challenge model.
Materials and methods:
The study was conducted in central Iowa. Clean-caught, colostrum-deprived calves were isolated individually at birth. Forty four calves were enrolled and weighed at birth and 10, 24, and 31 days of age. Fecal samples were collected daily and fecal consistency scored twice daily through 31 days. All calves were fed 2 quarts of commercial milk replacer twice daily. Calves were blocked into pairs based on birth order and randomly assigned either the C. parvum test article (n=22) or placebo (n=22), which was added to the first 14 feedings (i.e., for 7 days). Personnel were blinded to the treatment that was assigned to each calf. At 10 days of age, each calf was orally inoculated with 20,000 C. parvum oocysts. Fecal samples were assayed with a fluorescent antibody technique for titer of C. parvum oocysts. Data evaluated included clinical diarrhea, oocyst shedding, weight gain, and mortality rate.
Results:
Prior to their C. parvum challenge oocysts were not detected in the feces of any calf and mean daily fecal consistency score and average daily gain (ADG) did not vary significantly between groups. On days 4 through 7 after challenge inoculation, C. parvum treatment calves had significantly (P<0.05) lower mean fecal consistency scores than placebo calves. During the 14 day observation period immediately following challenge, all 22 placebo calves had a fecal consistency score ≥ 3 at least once, whereas only 15 of 22 (68%) of C. parvum treatment calves had any fecal consistency score ≥ 3. The morbidity score was ≥ 3 for 28% of placebo calf days and 12% of C. parvum treatment calf days. On days 2 through 7 after challenge the mean morbidity score for the C. parvum treatment was significantly (P<0.05) lower than that for the placebo. Incidence of oocyst fecal shedding was significantly (P<0.05) lower for the C. parvum treatment than the placebo on days 5 through 10 after challenge and mean fecal oocyst titer was significantly (P<0.05) less for the C. parvum treatment compared with that for the placebo on days 4 through 8 after challenge. During the 14 days immediately after challenge, ADG was significantly (P<0.05) higher (213%) for the C. parvum treatment, compared with placebo. During the 21-day observation period following challenge inoculation, none of the C. parvum treatment calves died, whereas 3 of 22 placebo calves died. The ADG, average daily scores and the total scores were evaluated using the Wilcoxon two-sample test, with two-sided t approximation (NPAR1WAY procedure in SAS, SAS Institute, Cary, NC). The percent of calves shedding C. parvum on each day of the study was evaluated using the FREQ procedure in SAS, with Fisher’s exact test to compare frequencies. The total number of days shedding was evaluated using the Wilcoxon test described above.
Significance:
Data presented in this study demonstrated that a safe and effective preparation has been developed as an aid in reducing the severity of disease and oocyst shedding due to Cryptosporidium parvum infections in young calves. All calves had similar clinical values and average daily weight gains during the 10 day pre-challenge (oral treatment) period supporting the safety claim of the product. The C. parvum test article was able to provide statistically significant reduced severity and duration of scours, significantly increased weight gain, significantly reduced oocyst shedding duration and rate, and prevention of mortality.
