A SURVEY ON BOVINE ROTAVIRUS TYPE 1-ASSOCIATED NEONATAL CALF DIARRHEA IN A BEEF HERD

An epizootiological survey was conducted on neonatal calf diarrhea in a beef herd for one calving season in 1981. Diarrhea occurred synchronously among calves on May 8-10, when the population density of the newborn reached a peak. The direct key factor for onset of illness was the succession of large changes in ambient temperature between daytime and nighttime. The main causative agent was diagnosed as bovine rotavirus (BRV) type 1 from the elevation of serum antibody titers, enzyme immunoassay of feces, and virus isolation. No antibody titer or no significant rise of the titer was detected against BRV type 2, BRV type 3, bovine coronavirus, or bovine viral diarrhea-mucosal disease virus. Two strains of Escherichia coli K99(+)Ent(+) and several strains of enteroviruses were also isolated. During the incidence of diarrhea, there was a gradual decrease in antibody titer against BRV type 1 in calf serum transferred via colostrum. This titer increased over a period from July to November, when diarrhea was scarcely observed. BRV antigen was first detected in normal feces of a cow on the day of parturition, then in those of her calf on the next day, and finally in the diarrheal feces of many calves on the day of outbreak, May 10. There were cases of asymptomatic or repeated infectioned. Direct relationships were not always observed among symptoms, elevation of antibody titer, and excretion of viruses.