An outbreak of so-called bovine influenza occurred throughout Japan over a period from October, 1968, to April, 1969. A total of 42, 756 cattle were involved and 153 cattle died, were condemned or sacrificed. The case fatality rate was 0.40%.
The main symptoms manifested consisted of a fever(39.0-42.0°C), polypnea, coughing, abundant rhinorrhea, lacrimation, salivation accompanied by copious foams and occasionally by blood, and leukopenia. They almost disappeared after about 10 days. Autopsy revealed severe pulmonary emphysema and hepatization in almost all cases.
Spontaneously infected cattle were examinedserologically for neutralizing or hemagglutinationinhibiting antibody against known viruses of bovine origin. They had no relations to bovine epizootic fever, Ibaraki, or infectious rhinotracheitis virus. Some of them showed a significant increase in antibody titer against bovine diarrhea virus, bovine adenovirus type 6, and parainfluenza virus type 3. None of these viruses, however, seemed to be incriminated for the present outbreak. The etiology of the so-called bovine influenza remained unknown.
