A survey of bovine coronavirus infections in cattle with respiratory disease in Chiba Prefecture, Japan

Bovine coronaviruses (BCoVs) cause gastrointestinal and respiratory symptoms in cattle, resulting in economic losses in the industry. The virus strains are endemic in many countries worldwide, including Japan. As recent epidemiological data on BCoVs in Japan are limited, we conducted a survey in Chiba Prefecture, where no such survey has been conducted before, using nasal swab or lung samples collected from 105 cattle with respiratory symptoms during 2020-2022. The rate of BCoV RNA positivity determined using real-time RT-PCR was 43.8% (46 samples), among which 20 strains were successfully isolated. Phylogenetic analysis based on the polymorphic sequence region of the spike gene classified the detected strains into the Japan G3 or G4 genotypes. Therefore, in contrast to previous report that BCoVs of the G3 genotype may have gone extinct in Japan, our results suggest that the Japan G3 and G4 genotypes coexist and have spread in Chiba Prefecture, causing respiratory disease in cattle.