June 28, 2016
By Tom Shelton, D.V.M.
Coronavirus has long been identified as a leading cause of calf scours and winter dysentery in adult cows. With this post, we begin a two-part series that looks at the possible role of coronavirus in bovine respiratory disease.
Recent improvements in diagnostic testing have identified bovine coronavirus (BCoV) as a possible agent in the cause of bovine respiratory disease (BRD). BCoV has traditionally been difficult to culture in the lab. Newer diagnostic tests, such as the polymerase chain reaction (PCR), have facilitated the identification of these viruses.
Uncomplicated BCoV infections are usually seen as acute infections with a short duration of virus shedding from three to eight days. It is best to collect tissue samples at the onset of disease or shortly after due to the acute transient nature of BCoV infection.
In 2008, the Wisconsin Veterinary Diagnostic Laboratory (WVDL) validated a simple non-invasive technique to sample calves and cows for BRD. The method uses a double-guarded mare uterine swab that travels through the bottom of the nose and samples the back of the throat in the pharyngeal tonsillar region.
When pharyngeal swabs are coupled with antimicrobial susceptibility testing, veterinarians can make an informed decision on which BRD vaccines and antibiotics to use. Pharyngeal swabs work extremely well provided the animals are sampled when they first break with BRD (acute disease) and a sufficient number of animals (minimum of four) are tested so producers and veterinarians can get a snap shot of what BRD pathogens are involved in the respiratory disease outbreak.
The second part of this series will share results of WVDL research on the prevalence of BCoV and its role in respiratory disease.
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