A long-term animal experiment indicating persistent infection of bovine coronavirus in cattle.

A long-term animal experiment involving inoculation with bovine coronavirus (BCoV) was conducted to verify its persistent infection in cattle. Three colostrum-deprived Holstein calves were housed separately in individual rooms of a high-containment facility and inoculated with the BCoV strain Kumamoto/1/07. Until the end of the experiment (1,085, 700 and 280 days, respectively), viral RNAs were detected sporadically by RT-PCR and nested PCR from plasma, nasal discharge, and feces. Seroconversion and titer changes were validated by hemagglutination inhibition tests and neutralization tests. Among the samples, nasal discharge showed a higher viral positivity than feces, which seemed to be associated with positive detection in the plasma. These data demonstrate the existence of persistent infection of BCoV in the respiratory tissues of cattle.