September 2020
Bovine Corona Virus
By Drs. Gregg Hanzlicek and Sasha Thomason
One of the most common questions we receive from practitioners concerns Bovine corona virus’ (BCoV) role as a respiratory pathogen. This virus has been associated with neonatal diarrhea since first discovered in 1972, and for many years associated with Winter Dysentery in dairy herds.1 It was first discovered in calves with bovine respiratory disease (BRD) in 1982.2
Multiple published studies have not been able to demostrate Koch’s postulate in experimentally challenged calves to sufficiently prove a causal relationship between BCoV and respiratory disease. A few studies have able to indicate an association between the virus and BRD. 3,4,5 Most of the studies were conducted in non-mixed-infection, seemingly unstressed calves. Given that BRD is a multifactorial disease, the inability to fulfill the postulate under these study conditions does not necessarily prove that BCoV is not involved in the disease.
Bovine corona virus’ role in bovine respiratory is uncertain at this time; although, many field-samples submitted to KSVDL and the outbreaks we have investigated over the last five years do provide at least anectodal evidence that BCoV may play a role in calf BRD.
The graph below highlights the percentage of positive samples by sample type. A consistent percentage of both upper airway and lower respiratory tract samples have been found to be BCoV PCR positive over the previous five years.
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References:
1 Mebus CA. Neonatal calf diarrhea: Results of a field trial using reo-like virus vaccine. Vet Med Small Anim Clin 1972;67:173-178.
2 Thomas LH. A search for new microorganisms in calf pneumonia by inoculation of gnotobiotic calves. Res Vet Sci 1982;33:170-182.
3 Saif LJ. Experimentally induced coronavirus infections in calves: replication in the respiratory and intestinal tracts. Am J Vet Res 1986;47:1426-1432.
4 Park SJ. Dual enteric and respiratory tropisms of winter dysentery bovine coronavirus in calves. Arch Virol 1990;115:127-132.
5 Reynolds DJ. Studies on the relationship between coronaviruses from the intestinal and respiratory tract of calves. Arch Virol 1985;85:71-83.