Avian coronavirus explained

Avian coronavirus is a species of virus from the genus Gammacoronavirus that infects birds; since 2018, all gammacoronaviruses which infect birds have been classified as this single species.[1] The strain of avian coronavirus previously known as infectious bronchitis virus (IBV) is the only coronavirus that infects chickens. It causes avian infectious bronchitis, a highly infectious disease that affects the respiratory tract, gut, kidney and reproductive system.[2] [3] IBV affects the performance of both meat-producing and egg-producing chickens and is responsible for substantial economic loss within the poultry industry. The strain of avian coronavirus previously classified as Turkey coronavirus causes gastrointestinal disease in turkeys.

Classification

IBV is in the genus Gammacoronavirus,[4] or group 3,[5] with a non-segmented, positive-sense single-stranded RNA genome.[6]

It was previously the type species of its genus Igacovirus.[7] When there was only one genus of coronaviruses, the genus Coronavirus, it was the type species of the group of all known coronaviruses.[8]

Recombination

When two strains of coronavirus IBV infect a host they may recombine during genome replication.[9] Recombination appears to contribute to the genetic variation of the IBV genome found in nature.[10] [11]

Pathology

Respiratory system

When inhaled, virus will attach to glycoprotein receptors containing sialic acid on ciliated epithelial cells of the respiratory epithelium. The respiratory replication will result in loss of ciliary activity,[12] mucus accumulation, necrosis and desquamation, causing respiratory distress, râles and asphyxia. Local virus replication will result in viremia, spreading the infection into other tissues and organs. Other respiratory diseases of chickens (Mycoplasma gallisepticum, avian infectious laryngotracheitis (Gallid alphaherpesvirus 1), Newcastle disease (avian paramyxovirus 1), Avian metapneumovirus infection may be confused clinically to infectious bronchitis.

Kidney

Through viremia, some nephrotropic strains (most of high virulence) could infect the kidney epithelium in tubules and nephron, causing kidney failure. At gross examination, kidneys may appear swollen and pale in color and with urates in ureters

Reproductive system

In hens, the viremic IBV will also reach the oviduct, causing lesions in the magnum (the egg-white gland) and in the uterus (the egg-shell gland), leading to a sharp decline of egg production, shell-less, fragile or roughened shells eggs (uterus lesion) with watery whites (magnum lesion). Infection of chickens at puberty, during the oviduct development, will impede oviduct formation and destroy future laying capacity, resulting in "false layers". However, other diseases affecting layer chickens could lead to that condition.[13]

Vaccines

There are both attenuated vaccines and inactivated vaccines available. Their effectiveness is diminished by poor cross-protection. The nature of the protective immune response to IBV is poorly understood, but the surface spike protein, the amino-terminal S1 half, is sufficient to induce good protective immunity. Experimental vector IB vaccines and genetically manipulated IBVs—with heterologous spike protein genes—have produced promising results, including in the context of in ovo vaccination.

See also

Further reading

Notes and References

  1. de Wit . J.J. Sjaak . Cook . Jane K.A. . Spotlight on avian coronaviruses . Avian Pathology . August 2020 . 49 . 4 . 313–316 . 10.1080/03079457.2020.1761010 . free . 32374218.
  2. Casais, R.. Thiel, V.. Siddell, S.G.. Cavanagh, D.. Britton, P. . 2001 . Reverse genetics system for the avian coronavirus infectious bronchitis virus . Journal of Virology . 75. 12359–12369 . 10.1128/JVI.75.24.12359-12369.2001. 11711626. 24. 116132.
  3. Cavanagh, D. . 2001 . A nomenclature for avian coronavirus isolates and the question of species status . Avian Pathology . 30. 109–115 . 10.1080/03079450120044506. 19184884. 2. free .
  4. Bande. F. Arshad. SS. Omar. AR. Bejo. MH. Abubakar. MS. Abba. Y. Pathogenesis and diagnostic approaches of Avian Infectious Bronchitis. Advances in Virology. 2016. 2016. 4621659. 10.1155/2016/4621659. 26955391. 4756178. free.
  5. Cavanagh. D. Coronavirus avian infectious bronchitis virus. Veterinary Research. 2007. 38. 2. 281–97. 10.1051/vetres:2006055. 17296157. free.
  6. de Vries, A.A.F. . Horzinek, M.C. . Rottier, P.J.M. . de Groot., R.J. . 1997 . The genome organisation of the Nidovirales: similarities and differences between arteri-, toro-, and coronaviruses. . Seminars in Virology . 8 . 1 . 33–547 . 10.1006/smvy.1997.0104. 32288441 . 7128191 . 10.1.1.462.1825 .
  7. Web site: ICTV Taxonomy history: Avian coronavirus . International Committee on Taxonomy of Viruses (ICTV) . 20 May 2021.
  8. Encyclopedia: Cann . Alan . Microbiology @ Leicester . Coronaviruses . 2020-06-15 . 2006 . University of Leicester, School of Biological Sciences . https://web.archive.org/web/20070309144307/http://www-micro.msb.le.ac.uk/3035/Coronaviruses.html . 2007-03-09 . Family: Coronaviridae; (Subfamily): ; Genus: Coronavirus; Type Species: Infectious bronchits virus.
  9. Kottier . S.A. . Cavanagh . D . Britton . P . Experimental evidence of recombination in coronavirus infectious bronchitis virus. . Virology . 10 November 1995 . 213 . 2 . 569–80 . 10.1006/viro.1995.0029 . free . 7491781 . 7131336.
  10. Wang . L . Junker . D . Collisson . E.W. . Evidence of natural recombination within the S1 gene of infectious bronchitis virus. . Virology . February 1993 . 192 . 2 . 710–6 . 10.1006/viro.1993.1093 . 8380672.
  11. Jia . W . Karaca . K . Parrish . C.R. . Naqi . S.A. . A novel variant of avian infectious bronchitis virus resulting from recombination among three different strains. . Archives of Virology . 1995 . 140 . 2 . 259–71 . 10.1007/BF01309861 . free . 7710354 . 7086685.
  12. Web site: Ciliary activity of chicken tracheal epithelial cells . https://ghostarchive.org/varchive/youtube/20211221/40Vxq5I22pM . 2021-12-21 . live. YouTube . 2010-11-15 . 2013-09-23.
  13. Web site: Infectious Bronchitis: Introduction . The Merck Veterinary Manual . 2006 . 2007-06-17 . https://web.archive.org/web/20070622113318/http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm%2Fbc%2F206500.htm . 22 June 2007 . live .

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