- Infectious Diseases of Livestock
- Part 2
- GENERAL INTRODUCTION: CORONAVIRIDAE
- GENERAL INTRODUCTION: PARAMYXOVIRIDAE AND PNEUMOVIRIDAE
- Equid herpesvirus 1 and equid herpesvirus 4 infections
- Teschen, Talfan and reproductive diseases caused by porcine enteroviruses
- Peste des petits ruminants
- GENERAL INTRODUCTION: CIRCOVIRIDAE AND ANELLOVIRIDAE
- Parainfluenza type 3 infection
- Bovine respiratory syncytial virus infection
- Hendra virus infection
- Paramyxovirus-induced reproductive failure and congenital defects in pigs
- Nipah virus disease
- GENERAL INTRODUCTION: CALICIVIRIDAE AND ASTROVIRIDAE
- Vesicular exanthema of swine
- Enteric caliciviruses of pigs and cattle
- GENERAL INTRODUCTION: RETROVIRIDAE
- Enzootic bovine leukosis
- Caprine arthritis-encephalitis
- Equine infectious anaemia
- GENERAL INTRODUCTION: PAPILLOMAVIRIDAE
- Papillomavirus infection of ruminants
- Papillomavirus infection of equids
- GENERAL INTRODUCTION: ORTHOMYXOVIRIDAE
- Equine influenza
- Swine influenza
- GENERAL INTRODUCTION: CORONAVIRIDAE
- Porcine transmissible gastroenteritis
- Porcine respiratory coronavirus infection
- Porcine epidemic diarrhoea
- Porcine haemagglutinating encephalomyelitis virus infection
- Porcine deltacoronavirus infection
- Bovine coronavirus infection
- Ovine coronavirus infection
- Equine coronavirus infection
- GENERAL INTRODUCTION: PARVOVIRIDAE
- Porcine parvovirus infection
- Bovine parvovirus infection
- GENERAL INTRODUCTION: ADENOVIRIDAE
- Adenovirus infections
- GENERAL INTRODUCTION: HERPESVIRIDAE
- Equid herpesvirus 2 and equid herpesvirus 5 infections
- Equine coital exanthema
- Infectious bovine rhinotracheitis/infectious pustular vulvovaginitis and infectious pustular balanoposthitis
- Bovine alphaherpesvirus 2 infections
- Malignant catarrhal fever
- Suid herpesvirus 2 infection
- GENERAL INTRODUCTION: ARTERIVIRIDAE
- Equine viral arteritis
- Porcine reproductive and respiratory syndrome
- GENERAL INTRODUCTION: FLAVIVIRIDAE
- Bovine viral diarrhoea and mucosal disease
- Border disease
- Hog cholera
- Wesselsbron disease
- Louping ill
- West nile virus infection
- GENERAL INTRODUCTION: TOGAVIRIDAE
- Equine encephalitides caused by alphaviruses in the Western Hemisphere
- Getah virus infection
- GENERAL INTRODUCTION: BUNYAVIRIDAE
- Diseases caused by Akabane and related Simbu-group viruses
- Rift Valley fever
- Nairobi sheep disease
- Crimean-Congo haemorrhagic fever
- GENERAL INTRODUCTION: ASFARVIRIDAE
- African swine fever
- GENERAL INTRODUCTION: RHABDOVIRIDAE
- Bovine ephemeral fever
- Vesicular stomatitis and other vesiculovirus infections
- GENERAL INTRODUCTION: REOVIRIDAE
- Ibaraki disease in cattle
- Epizootic haemorrhagic disease of deer
- African horse sickness
- Equine encephalosis
- Palyam serogroup orbivirus infections
- Rotavirus infections
- GENERAL INTRODUCTION: POXVIRIDAE
- Lumpy skin disease
- Sheeppox and goatpox
- Ulcerative dermatosis
- Bovine papular stomatitis
- GENERAL INTRODUCTION: PICORNAVIRIDAE
- Encephalomyocarditis virus infection
- Swine vesicular disease
- Equine picornavirus infection
- Bovine rhinovirus infection
- Foot-and-mouth disease
- GENERAL INTRODUCTION: BORNAVIRIDAE
- Borna disease
- Post-weaning multi-systemic wasting syndrome in swine
- GENERAL INTRODUCTION: PRION DISEASES
- Unclassified virus-like agents, transmissible spongiform encephalopathies and prion diseases
- Bovine spongiform encephalopathy
- Transmissible spongiform encephalopathies related to bovine spongiform encephalopathy in other domestic and captive wild species
GENERAL INTRODUCTION: CORONAVIRIDAE
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L J SAIF - Professor, MS, PhD, Food Animal Health Research Program, CFAES and CVM, OARDC/The Ohio State University, 1680 Madison Ave, Wooster, Ohio, OH 44691, USA
The families Coronaviridae and Arteriviridae with five genera (Dipartevirus, Equartevirus, Nesartevirus, Porartevirus, and Simartevirus), have been classified together in the order Nidovirales.1, 2 Within the Coronaviridae, the there are two subfamilies, the Corovirinae and Torovirinae. These subfamilies contain four genera (Alphacoronavirus, Betacoronavirus, Gammacoronavirus and Deltacoronavirus) and potentially two genera (Bafinivirus, Torovirus as well as three viruses so far unassigned to a genus), respectively.1, 2, 9, 14, 15
The word ‘nidus’ is Latin for nest and refers to the fact that all viruses in this order use a unique and similar replication strategy, the so-called ‘nested set transcription’ strategy. Members of the Coronaviridae are enveloped and pleomorphic, with an overall diameter of 60-190 nm; they have a large, single-stranded, positive sense RNA genome of approximately 25.4-28 kb. The coronaviruses were so named because of the unusually large, club-shaped glycoproteins or spikes projecting from the envelope, that give the virion the appearance of a solar corona. 9-11, 13 The name torovirus is derived from ‘torus’ or doughnut-shape of the virions.6, 7
All members of the Coronaviridae contain at least four structural proteins: a large heavily glycosylated envelope glycoprotein S (for spike), a transmembrane glycoprotein M (for membrane), a small integral membrane envelop protein and a nucleoprotein (N) that encapsulates the viral RNA.2, 3, 9, 11, 14 Some coronaviruses, such as bovine and some murine coronaviruses, and the bovine torovirus also have a haemagglutininesterase (HE) protein.3, 6, 9, 10, 14
The Aphacoronavirus and Betacoronavirus genera are subdivided into species or subgroups (A, B, C, D, etc), and they contain viruses of pigs, cattle and horses, as well as cats, dogs, mice, rats and humans. Gammacoronaviruses contain mostly avian coronaviruses, whereas Deltacoronaviruses contain avian and a few mammalian coronaviruses (Asian leopard, cat, swine).2, 9, 14, 15
The global emergence of two zoonotic coronavirus infections, the Severe Acute Respiratory Syndrome (SARS) (Betacoronavirus B) in 2003 and the unrelated Middle East Respiratory Syndrome (MERS) (Betacoronavirus C) a decade later, demonstrated the newly recognized pandemic potential of these zoonotic infections.9, 12, 14 Both SARS and MERS coronaviruses are suspected to have evolved from a bat-host reservoir via carnivore (civet species) or camelid (dromedary camels) intermediate hosts.12, 14, 5 Bats are the supposed host reservoir for these alpha and beta coronaviruses and the putative ancestral coronavirus for all mammalian coronaviruses.14, 15
Although emergence of cornaviruses causing fatal pneumonia in human adults (SARS, MERS) stunned the medical community, veterinary scientists had previously established that coronaviruses cross species barriers to emerge as new strains or mutants causing severe or fatal enteric and respiratory infections in animals.13, 14 Coronaviruses of livestock generally cause acute infections of the respiratory or enteric tracts and transmission occurs mainly by the faecal-oral or respiratory routes.
Many of these viruses are widespread and the infections range from severe to mild or subclinical. However, infection of young piglets by several enteric coronaviruses, such as transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhoea virus (PEDV) is devastating due to the high morbidity (up to 100%) and mortality (up to 100%).8, 11, 16 High morbidity (100%) but lower mortality is also evident in neonatal pigs infected with porcine Deltacoronavirus (PDCoV).5
To date, five distinct coronaviruses have been identified in pigs that consist of three Alphacoronaviruses, one Betacoronavirus, and one Deltacoronavirus.5, 8, 11, 14, 16 TGEV (Alphacoronavirus), first identified in diarrheic pigs in 1946, is enteric and causes severe diarrhoea and mortality in young pigs.
The association of coronaviruses with pigs is complex but can be summarised as follows:
- Porcine respiratory coronavirus (PRCV) (Alphacoronavirus), which is a deletion mutant of TGEV, was isolated in 1984. It has a major deletion in the S gene and smaller deletions or mutations in open reading frame 3 genes. Unlike TGEV, PRCV replicates in the respiratory tract and causes mostly subclinical infections. Interestingly, TGEV outbreaks have decreased in Europe after PRCV became widespread.
- PEDV (Alphacoronavirus), first isolated from diarrheic pigs in 1977, is also an enteric infection and causes severe diarrhoea and mortality in young pigs.
- Haemagglutinating encephalomyelitis virus (HEV) (betacoronavirus), isolated in 1962, is the causative agent of vomiting and wasting disease.
- PDCoV (Deltacoronavirus) identified in 2012, is also an enteric infection and causes milder diarrhoea and lower mortality in young pigs, as compared with PEDV or TGEV infection of young pigs.
In cattle and sheep, including wild ruminants, bovine coronavirus (BCV) (Betacoronavirus A) causes neonatal diarrhoea or contributes to multifactorial respiratory tract disease in calves; it is also responsible for winter dysentery in older cattle.10, 13, 14 In horses, equine coronavirus (ECV) (Betacoronavirus A) has occasionally been associated with diarrhoea in foals, and it is closely related to bovine coronavirus and to porcine haemagglutinating encephalomyelitis virus.4
The genus Torovirus contains three viruses identified in cattle, horses, and pigs.6, 7
- Bovine torovirus (BoTV), originally named Breda virus;
- Equine torovirus (ETV), formerly Berne virus;
- Porcine torovirus (PoTV)
These viruses have been associated with diarrhoea in cattle, horses and pigs but their pathogenic potential and clinical significance remain unclear.
In summary coronaviruses cause predominantly enteric and respiratory disease, sometimes fatal, in domestic animals and wildlife. They also cause the common cold and severe and often fatal zoonotic respiratory infections in humans (SARS, MERS). Their genetic and host diversity and potential for interspecies transmission has only recently been widely recognized and accepted.
- International Committee on Taxonomy of Viruses https://talk.ictvonline.org/taxonomy/ (Accession date: 21/26/2017).
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