Rapid diagnosis of bovine coronavirus infection and its seasonal and age dependence in Korean native calves

Abstract

Bovine coronavirus (BCoV) is an important viral pathogen responsible for diarrhea in neonatal and young calves, leading to significant economic losses in the cattle industry worldwide. Despite its impact, field-level data on BCoV infection in Korean cattle farms remain limited. In this study, we investigated the prevalence of BCoV among pre-weaned calves presenting with diarrhea in Gimje, Jeollabuk-do Province, Republic of Korea. A total of 406 diarrheic calves, ranging in age from 2 to 120 days and originating from 169 farms, were tested for BCoV antigen using a rapid diagnostic kit suitable for on-site application in livestock farms. The overall prevalence of BCoV was found to vary by season and age. Seasonal analysis revealed infection rates of 20.0% in autumn and 8.5% in winter, which were considerably higher compared with spring (3.3%) and summer (1.7%). Age-specific infection rates were highest in calves at one week (12.3%) and two weeks (4.6%) of age, whereas the prevalence dropped below 3.0% from 3 to 120 days of age. These results suggest that BCoV infections occur more frequently under low-temperature conditions and in younger, more susceptible calves. In conclusion, this study provides field-based evidence of BCoV occurrence in diarrheic calves in Korea and highlights the value of rapid diagnostic kits as a practical tool for the early detection of BCoV at the farm level. Effective monitoring and timely management of BCoV may contribute to improved calf health, enhanced farm productivity, and better animal welfare outcomes.