Bovine Coronavirus and the Associated Diseases

Abstract

Coronaviruses (CoVs) possess the largest and most complex RNA genome (up to 32 kb) that encodes for 16 non-structural proteins regulating RNA synthesis and modification. Coronaviruses are known to infect a wide range of mammalian and avian species causing remarkably diverse disease syndromes. Variable tissue tropism and the ability to easily cross interspecies barriers are the well-known characteristics of certain CoVs. The 21st century epidemics of severe acute respiratory CoV (SARS-CoV), Middle East respiratory CoV and the ongoing SARS-CoV-2 pandemic further highlight these characteristics and emphasize the relevance of CoVs to the global public health. Bovine CoVs (BCoVs) are betacoronaviruses associated with neonatal calf diarrhea, and with winter dysentery and shipping fever in older cattle. Of interest, no distinct genetic or antigenic markers have been identified in BCoVs associated with these distinct clinical syndromes. In contrast, like other CoVs, BCoVs exist as quasispecies. Besides cattle, BCoVs and bovine-like CoVs were identified in various domestic and wild ruminant species (water buffalo, sheep, goat, dromedary camel, llama, alpaca, deer, wild cattle, antelopes, giraffes, and wild goats), dogs and humans. Surprisingly, bovine-like CoVs also cannot be reliably distinguished from BCoVs using comparative genomics. Additionally, there are historical examples of zoonotic transmission of BCoVs. This article will discuss BCoV pathogenesis, epidemiology, interspecies transmission, immune responses, vaccines, and diagnostics.

Keywords: bovine coronavirus; bovine respiratory disease complex; cattle; diarrhea; enteric; respiratory; wild ruminants.

Figure 1

Summary diagram of different clinical syndromes associated with BCoV and challenges for successful vaccination associated with different ages/production status of cattle. CD, calf diarrhea; WD, winter dysentery; BRDC, bovine respiratory disease complex. Coronavirus image placed above animal represents potential carrier status. Rectangle boxes list unknown host and vaccine-associated factors that can result in suboptimal vaccine performance or lack of protection of cattle of different ages.

Figure 2

Phylogenetic analysis of complete genomes of enteric and respiratory BCoVs and bovine-like CoVs from wild ruminants. The evolutionary history was inferred by using the Maximum Likelihood method and General Time Reversible model. The tree with the highest log likelihood (−81,750.81) is shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. This analysis involved 53 nucleotide sequences. Evolutionary analyses were conducted in MEGA X (39). Black triangle markers are used for bovine-like CoVs isolated from wild ruminants, and black round markers are used to mark respiratory BCoVs. The collapsed branch includes a cluster of recent BCoV strains from Japan (35).