Coronavirus replication in the intestinal and respiratory tracts during infection of calves.

Coronaviruses have been isolated from cases of neonatal calf diarrhoea in many parts of the world and were revealed in the respiratory tract recently, during a study of calf pneumonia. In experiments on gnotobiotic calves an enteric coronavirus replicated in the nasal epithelium and a respiratory isolate was shed in faeces. The enteric coronavirus prevented subsequent infection with either homologous enteric or the respiratory isolate. A dual tropism for this agent was emphasized by the detection of coronavirus antigen in intestinal and respiratory epithelium of naturally-infected calves.