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strand and is coated by the N protein (nucleocapsid). IBV diversity, as for all RNA viruses, may occur as transcriptional error and nucleotide substitution. Nucleotide variants (genotypes), in the gene encoding the distal S protein region (S1), may become very relevant if a different amino acid (non-synonymous) is encoded, and the new phenotype has different biological properties (strain). Amino acid changes located in the receptor binding domain of the S1 spike protein region, involved in the adsorption to the cellular receptor (
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The coronaviruses contain the largest known viral RNA genome in number of nucleotides, of approximately 30,000 bases. The virions are enveloped and characterized by large surface projections (spikes or S) partially embedded in the double lipid layer. The genome consists of RNA of a single monopartite
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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
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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
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primers designed and target gene. Broadly sensitive universal gene targets are the nucleoprotein, the matrix or the S2 encoding genes. The S1 encoding gene products sequencing may enable phylogenetic results which are comparable to serotyping. Methods for IBV antigens detection may employ labelled
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of cell-surface glycoprotein), may evade neutralization by antibodies, although still capable of adsorption to cell receptor and fusion. As a result of selective pressure, variants may infect chickens with immunity to heterologous variants and emerge with evolutional advantage. In addition, large
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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
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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.
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described and varies greatly genetically and phenotypically, with hundreds of serotypes and strains described. The most updated classification of IBV places the virus in
Coronaviridae, Orthocoronavirinae, genus
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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.
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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:
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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
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Chicken respiratory diseases are difficult to differentiate and may not be diagnosed based on respiratory signs and lesions. Other diseases such as mycoplasmosis by
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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.
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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.
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Definitive diagnosis relies on viral isolation and characterization. For virus characterization, the methodology using genomic amplification (
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in some stages may clinically resemble IB. Similar kidney lesions may be caused by different etiologies, including other viruses, such as
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incubation. Normally-colored eggs, indicative of normal shells for instance in brown chickens, have a normal hatchability.
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antibodies, such as direct immunofluorescence or immunoperoxidase. Antibodies to IBV may be detected by indirect
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Egg yield curve may never return to normal. Milder strains may allow normal production after around eight weeks.
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IBV infect a host cell, reassortment may occur, and appears to contribute to the genetic variation of the IBV
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inhibition (haemagglutinating IBV produced after enzymatic treatment by phospholipase C).
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are produced, which enable reassortment in coinfections. When two strains of
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In laying hens, abnormal and reduced egg production are also observed in
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are important in controlling the spread of the infection and disease.
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genomic changes will occur with entire gene segments interchanges by
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virus (the cause of
Gumboro disease) and toxins (for instance
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protocols, including adequate distancing of flocks,
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232:by mesogenic strains of Newcastle diseases virus (
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385:"International Committee on Taxonomy of Viruses"
491:The Infectious Bronchitis (IB) information site
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321:Different vaccine formulations are available (
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389:International Committee on Taxonomy of Virus
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314:No specific treatment is available, but
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349:strain vaccines, such as H120 and Ma5.
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410:"Infectious Bronchitis: Introduction"
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383:Martins, Nelson (January 16, 2020).
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521:Coronavirus-associated diseases
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484:Avian infectious bronchitis
414:The Merck Veterinary Manual
58:. The disease is caused by
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25:Avian infectious bronchitis
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251:infectious bursal disease
345:) for the active (live)
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225:Mycoplasma gallisepticum
516:Animal viral diseases
486:at Wikimedia Commons
239:Avian metapneumovirus
277:(EDS), caused by an
275:Egg Drop Syndrome 76
87:respiratory distress
52:respiratory disease
36:Veterinary medicine
179:IBV was the first
68:Orthocoronavirinae
482:Media related to
304:Haemagglutination
296:immunofluorescent
230:Newcastle disease
157:Soft-shelled eggs
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353:Biosecurity
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260:Aspergillus
255:ochratoxins
214:in nature.
208:coronavirus
195:sialic acid
190:Igacovirus.
188:, subgenus
181:coronavirus
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456:PMC7131336
424:2007-06-17
367:References
76:Igacovirus
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264:ochraceus
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91:nephritis
62:(IBV), a
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234:APMV-1
212:genome
300:ELISA
204:mRNAs
175:Cause
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396:2020
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332:WHO
287:PCR
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