Rotavirus infections in calves. II. Experimental infections with a Dutch isolate.

Rotaviruses were observed electron microscopically in clarified faecal samples from calves with diarrhoea. Several herds with a history of scouring among neonatal calves were shown to be infected with rotaviruses. A bacteria-free faecal filtrate from a rotavirus positive sample administered orally induced diarrhoea in one out of two colostrum-deprived calves. Both calves excreted rotaviruses in their faeces and serum antibody responses were demonstrated by complement-fixation and indirect immunofluorescence tests and by immune electron microscopy. Purified rotavirus from faeces of the first calf induced profuse diarrhoea in three other colostrum-deprived calves, with subsequent shedding of the virus in the faeces. These calves also showed a serum antibody response. All calves recovered in one to seven days without treatment. Two colostrum-fed calves were removed from a rotavirus-affected dairy farm within 36 hours after birth and studied at the Institute. Both animals excreted rotaviruses and developed severe diarrhoea, although they had circulating maternal antibodies. Attempts to grow this rotavirus in cell cultures were not successful.