Overview of Coronaviruses in Veterinary Medicine

Coronaviruses infect humans and a wide range of animals, causing predominantly respiratory and intestinal infections. This review provides background on the taxonomy of coronaviruses, the functions of viral proteins, and the life cycle of coronaviruses. In addition, the review focuses on coronaviral diseases in several agriculturally important, companion, and laboratory animal species (cats, cattle, chickens, dogs, mice, rats and swine) and briefly reviews human coronaviruses and their origins.

Coronaviruses get their name from their morphology, as the spike proteins present in the envelope of the virus give the virions a crown-like (‘corona’) appearance when viewed by electron microscopy. Coronaviruses are enveloped, spherical or pleomorphic viruses ranging from 120 to 160 nm in diameter. Coronaviruses have the largest nonsegmented positive-sense single-stranded RNA viral genome (25 to 32,000 nucleotides).^22,69 The genome is polyadenylated and capped. Coronavirus genomes can serve as mRNAs, and purified genomic RNA is infectious. The arrangement of genes is similar for all coronaviruses, with the nonstructural replicase gene encoded in the 5′ two thirds of the genome, and the genes for the structural proteins and several small accessory proteins encoded in the 3′ third of the genome.