Clinical manifestations of diarrhea in calves infected with rotavirus and enterotoxigenic Escherichia coli.

The susceptibility of gnotobiotic, colostrum-derived, or suckling calves to four bovine rotavirus isolates was found to be age dependent. Calves older than 7 days remained clinically normal, although they excreted virus in their feces and subsequently developed antibody against the virus, Enterotoxigenic Escherichia coli, fed to gnotobiotic, colostrum-deprived, or suckling calves ranging in age from a few hours to 26 days old, only caused diarrhea in animals younger than 24 h old. In contrast, diarrhea was consistently induced in 1- and 2-week-old calves infected with both enterotoxigenic E. coli and rotavirus. In general, diarrhea appeared after a rotavirus incubation period of approximately 3 days and was independent of the order in which the two microbial agents were given, the age of the calf, or the level of circulating rotavirus antibodies. The disease episode coincided with the excretion of rotavirus, rather than enterotoxigenic E. coli, in the feces. Infection with enterotoxigenic E. coli became established within 24 h of inoculation, and in older calves enterotoxigenic E. coli was often excreted in very small numbers and for a longer period than rotavirus.