[Participation of coronaviruses in the etiology of respiratory diseases in calves].

Sizov, I; Mitov, B; Kharalambiev, Kh E

Studied was the Bovine corona virus as taking part in the epizootiology of respiratory diseases in calves. On 4 out of the 7 investigated farms there was a rise of the antibodies against the virus. Two strains were isolated from 2 diseased calves, using tissue culture of trachea. They were the III 213/81 and III 214/81 strains and were identified as bovine corona viruses. Test calves experimentally infected via the trachea with the III 214/81 strain responded with a slight and transient rise of body temperature and a slight cough. The virus was reisolated from the nasal discharge of 3 diseased calves as well as from the feces of one affected calf. The direct immunofluorescence method was employed to establish cytoplasmic fluorescence between the 4th and the 8 h day of infection. The immune response observed with the infected animals confirmed the development of the corona-virus infection. The clinical observations with calves on both the farms with spontaneous infections and those with experimentally induced infections showed that the bovine corona virus could not cause a strongly manifested respiratory disease.