Prevalence of coronavirus from diarrheic calves in the Republic of Korea

Objective: To investigate the prevalence of bovine coronavirus (BCoV), bovine rotavirus, and bovine viral diarrhea virus in the feces of normal and diarrheic Korean native calves aged 1-81 days between April and October of 2016 in the Republic of Korea. Methods: Samples were obtained from 50 normal and 93 diarrheic (56 semi-formed, 28 loose, and 9 watery feces) calves in six different regions of northern and southern Korea. These fecal samples were tested for BCoV, bovine rotavirus, and bovine viral diarrhea virus by RT-PCR. Results: Among the three pathogens examined, infection with BCoV was especially prominent in relation to diarrhea among calves aged 1-21 days [odds ratio (OR)=9.3, 95% confidence interval (CI): 1.1-78.9; P=0.02). Infection with BCoV alone (OR=2.9; 95% CI: 1.1-7.6; P=0.03) or co-infection of BCoV with bovine viral diarrhea virus (OR=3.6; 95% CI: 1.0-12.4; P=0.04) was significantly associated with the development of loose feces. Grazing and colostrum intake strongly reduced the occurrence of diarrhea as compared to housed calves (OR=0.2; 95% CI: 0.1-0.4; P=0.00) and calves that had not been fed colostrum (OR=0.2; 95% CI: 0.1-0.7; P=0.02), respectively. Conclusions: The present study suggests that BCoV is involved in calf diarrhea in the Republic of Korea. Therefore, grazing and colostrum intake is recommended for preventing and controlling calf diarrhea caused by BCoV.