Prevalence of coronavirus from diarrheic calves in the Republic of Korea

Objective: To investigate the prevalence of bovine coronavirus(BCo V), 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 BCo V, bovine rotavirus, and bovine viral diarrhea virus by RT-PCR. Results: Among the three pathogens examined, infection with BCo V 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 BCo V alone(OR=2.9; 95% CI: 1.1-7.6; P=0.03) or coinfection of BCo V 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 BCo V 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.