Avian infectious bronchitis

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Avian infectious bronchitis
SpecialtyVeterinary medicine

Avian infectious bronchitis (IB) is an acute and highly contagious

rales, and nasal discharge. In young chickens, severe respiratory distress may occur. In layers, respiratory distress, nephritis, decrease in egg production, and loss of internal (watery egg white) and external (fragile, soft, irregular or rough shells, shell-less) egg quality are reported.[2][3]

Clinical signs

Coughing and rattling are common, most severe in young, such as broilers, and rapidly spreading in chickens confined or at proximity. Morbidity is 100% in non-vaccinated flocks. Mortality varies according to the virus strain (up to 60% in non-vaccinated flocks). Respiratory signs will subdue within two weeks. However, for some strains, a kidney infection may follow, causing mortality by toxemia. Younger chickens may die of tracheal occlusion by mucus (lower end) or by kidney failure. The infection may prolong in the cecal tonsils.[citation needed]

In laying hens, there can be transient respiratory signs, but mortality may be negligible. However, egg production drops sharply. A great percentage of produced eggs are misshapen and discolored. Many laid eggs have a thin or soft shell and poor albumen (watery), and are not marketable or proper for incubation. Normally-colored eggs, indicative of normal shells for instance in brown chickens, have a normal hatchability.[citation needed]

Egg yield curve may never return to normal. Milder strains may allow normal production after around eight weeks.

  • Egg yield curve in BI in a parent flock
    Egg yield curve in BI in a parent flock
  • Thin-shelled egg
    Thin-shelled egg
  • Abnormal granulations on shell
    Abnormal granulations on shell
  • Soft-shelled eggs
    Soft-shelled eggs
  • Misshapen and discolored eggs
    Misshapen and discolored eggs

Cause

IBV was the first

mRNAs are produced, which enable reassortment in coinfections. When two strains of coronavirus IBV infect a host cell, reassortment [5] may occur, and appears to contribute to the genetic variation of the IBV genome in nature.[6]

Diagnosis

Chicken respiratory diseases are difficult to differentiate and may not be diagnosed based on respiratory signs and lesions. Other diseases such as mycoplasmosis by

Newcastle disease by mesogenic strains of Newcastle diseases virus (APMV-1), Avian metapneumovirus, infectious laryngotracheitis, avian infectious coryza Avibacterium paragallinarum in some stages may clinically resemble IB. Similar kidney lesions may be caused by different etiologies, including other viruses, such as infectious bursal disease virus (the cause of Gumboro disease) and toxins (for instance ochratoxins of Aspergillus ochraceus), and dehydration.[citation needed
]

In laying hens, abnormal and reduced egg production are also observed in Egg Drop Syndrome 76 (EDS), caused by an Atadenovirus and avian metapneumovirus infections. At present, IB is more common and far more spread than EDS. The large genetic and phenotypic diversity of IBV have been resulting in common vaccination failures. In addition, new strains of IBV, not present in commercial vaccines, can cause the disease in IB vaccinated flocks. Attenuated vaccines will revert to virulence by consecutive passage in chickens in densely populated areas, and may reassort with field strains, generating potentially important variants.[citation needed]

Definitive diagnosis relies on viral isolation and characterization. For virus characterization, the methodology using genomic amplification (

Haemagglutination
inhibition (haemagglutinating IBV produced after enzymatic treatment by phospholipase C).

Treatment and prevention

No specific treatment is available, but

antibiotics can be used to prevent secondary infections.[citation needed
]

Different vaccine formulations are available (

lyophilized
strain vaccines, such as H120 and Ma5.

disinfection
are important in controlling the spread of the infection and disease.

References

  1. ^ a b Martins, Nelson (January 16, 2020). "International Committee on Taxonomy of Viruses". International Committee on Taxonomy of Virus. Retrieved January 16, 2020.
  2. ^ "Infectious Bronchitis: Introduction". The Merck Veterinary Manual. 2006. Archived from the original on 22 June 2007. Retrieved 2007-06-17.
  3. ^ Cavanagh, D., and S. A. Naqi. Infectious bronchitis. In: Diseases of poultry, 11th ed. Y. M. Saif, ed. Iowa State University Press, Ames, IA. pp. 101–120. 2003.
  4. ^ Almeida, J. D., D. M. Berry, C. H. Cunningham, D. Hamre, M. S. Hofstad,. L. Mallucci, K. McIntosh, and D. A. J. Tyrrell. 1968. Coronaviruses. Nature 220:650.
  5. ^ Kottier SA, Cavanagh D, Britton P. Experimental evidence of recombination in coronavirus infectious bronchitis virus. Virology. 1995 Nov 10;213(2):569-80. doi: 10.1006/viro.1995.0029. PMID 7491781; PMCID: PMC7131336
  6. ^ Wang L, Junker D, Collisson EW. Evidence of natural recombination within the S1 gene of infectious bronchitis virus. Virology. 1993 Feb;192(2):710-6. doi: 10.1006/viro.1993.1093. PMID 8380672

External links

Media related to Avian infectious bronchitis at Wikimedia Commons

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