Avian infectious bronchitis

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Avian infectious bronchitis
Specialty Veterinary medicine

Avian infectious bronchitis (IB) is an acute and highly contagious respiratory disease of chickens. The disease is caused by avian infectious bronchitis virus (IBV), a coronavirus (Coronaviridae, Orthocoronavirinae, genus Gammacoronavirus, subgenus Igacovirus), [1] and characterized by respiratory signs including gasping, coughing, sneezing, tracheal 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]

Contents

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.

Cause

IBV was the first coronavirus described [4] 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 Gammacoronavirus, subgenus Igacovirus. [1] 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 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 (sialic acid 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 genomic changes will occur with entire gene segments interchanges by reassortment, as during IBV replication, seven subgenomic 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 Mycoplasma gallisepticum (chronic respiratory disease), 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 (PCR), firstly by the reverse transcription of viral RNA into cDNA, the cyclic amplification of cDNA and sequencing of products, will enable very precise description of strains, according to the oligonucleotide 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 antibodies, such as direct immunofluorescence or immunoperoxidase. Antibodies to IBV may be detected by indirect immunofluorescent antibody test, ELISA and 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 (ATCvet codes: QI01AA03 ( WHO ) for the inactivated vaccines, typically oil-emulsioned and combined with other avian pathogens, and QI01AD07 ( WHO ) for the active (live) lyophilized strain vaccines, such as H120 and Ma5.

Biosecurity protocols, including adequate distancing of flocks, isolation and disinfection are important in controlling the spread of the infection and disease.

Related Research Articles

<span class="mw-page-title-main">Coronavirus</span> Subfamily of viruses in the family Coronaviridae

Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the common cold, while more lethal varieties can cause SARS, MERS and COVID-19, which is causing the ongoing pandemic. In cows and pigs they cause diarrhea, while in mice they cause hepatitis and encephalomyelitis.

<i>Influenza A virus</i> Species of virus

Influenza A virus (IAV) causes influenza in birds and some mammals, and is the only species of the genus Alphainfluenzavirus of the virus family Orthomyxoviridae. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon. Some isolates of influenza A virus cause severe disease both in domestic poultry and, rarely, in humans. Occasionally, viruses are transmitted from wild aquatic birds to domestic poultry, and this may cause an outbreak or give rise to human influenza pandemics.

<span class="mw-page-title-main">Avian influenza</span> Influenza caused by viruses adapted to birds

Avian influenza, known informally as avian flu or bird flu, is a variety of influenza caused by viruses adapted to birds. The type with the greatest risk is highly pathogenic avian influenza (HPAI). Bird flu is similar to swine flu, dog flu, horse flu and human flu as an illness caused by strains of influenza viruses that have adapted to a specific host. Out of the three types of influenza viruses, influenza A virus is a zoonotic infection with a natural reservoir almost entirely in birds. Avian influenza, for most purposes, refers to the influenza A virus.

<span class="mw-page-title-main">Virulent Newcastle disease</span> Contagious viral avian disease

Virulent Newcastle disease (VND), formerly exotic Newcastle disease, is a contagious viral avian disease affecting many domestic and wild bird species; it is transmissible to humans. Though it can infect humans, most cases are non-symptomatic; rarely it can cause a mild fever and influenza-like symptoms and/or conjunctivitis in humans. Its effects are most notable in domestic poultry due to their high susceptibility and the potential for severe impacts of an epizootic on the poultry industries. It is endemic to many countries. No treatment for VND is known, but the use of prophylactic vaccines and sanitary measures reduces the likelihood of outbreaks.

<i>Coronaviridae</i> Family of viruses in the order Nidovirales

Coronaviridae is a family of enveloped, positive-strand RNA viruses which infect amphibians, birds, and mammals. The group includes the subfamilies Letovirinae and Orthocoronavirinae; the members of the latter are known as coronaviruses.

Poultry diseases occur in poultry, which are domesticated birds kept for their meat, eggs or feathers. Poultry species include the chicken, turkey, duck, goose and ostrich.

<span class="mw-page-title-main">Infectious bursal disease</span> Viral disease of poultry

Infectious bursal disease (IBD), also known as Gumboro disease, infectious bursitis and infectious avian nephrosis, is a highly contagious disease of young chickens and turkeys caused by infectious bursal disease virus (IBDV), characterized by immunosuppression and mortality generally at 3 to 6 weeks of age. The disease was first discovered in Gumboro, Delaware in 1962. It is economically important to the poultry industry worldwide due to increased susceptibility to other diseases and negative interference with effective vaccination. In recent years, very virulent strains of IBDV (vvIBDV), causing severe mortality in chicken, have emerged in Europe, Latin America, South-East Asia, Africa and the Middle East. Infection is via the oro-fecal route, with affected bird excreting high levels of the virus for approximately 2 weeks after infection. The disease is easily spread from infected chickens to healthy chickens through food, water, and physical contact.

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. 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. 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.

Marek's disease is a highly contagious viral neoplastic disease in chickens. It is named after József Marek, a Hungarian veterinarian who described it in 1907. Marek's disease is caused by an alphaherpesvirus known as "Marek's disease virus" (MDV) or Gallid alphaherpesvirus 2 (GaHV-2). The disease is characterized by the presence of T cell lymphoma as well as infiltration of nerves and organs by lymphocytes. Viruses related to MDV appear to be benign and can be used as vaccine strains to prevent Marek's disease. For example, the related herpesvirus found in turkeys (HVT), causes no apparent disease in the birds, and continues to be used as a vaccine strain for prevention of Marek's disease.

<span class="mw-page-title-main">H5N1 genetic structure</span>

H5N1 genetic structure is the molecular structure of the H5N1 virus's RNA.

<span class="mw-page-title-main">Fujian flu</span> Strains of influenza

Fujian flu refers to flu caused by either a Fujian human flu strain of the H3N2 subtype of the Influenza A virus or a Fujian bird flu strain of the H5N1 subtype of the Influenza A virus. These strains are named after Fujian, a coastal province in Southeast China.

<span class="mw-page-title-main">Specific-pathogen-free</span>

Specific-pathogen-free (SPF) is a term used for laboratory animals that are guaranteed free of particular pathogens. Use of SPF animals ensures that specified diseases do not interfere with an experiment. For example, absence of respiratory pathogens such as influenza is desirable when investigating a drug's effect on lung function.

<span class="mw-page-title-main">Infectious bronchitis virus D-RNA</span>

The Infectious bronchitis virus D-RNA is an RNA element known as defective RNA or D-RNA. This element is thought to be essential for viral replication and efficient packaging of avian infectious bronchitis virus (IBV) particles.

<span class="mw-page-title-main">Influenza</span> Infectious disease, often just "the flu"

Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin from one to four days after exposure to the virus and last for about 2–8 days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia, which can be caused by the virus or by a subsequent bacterial infection. Other complications of infection include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.

Avian orthoreovirus, also known as avian reovirus, is an orthoreovirus from the Reoviridae family. Infection causes arthritis and tenosynovitis in poultry. It can also cause respiratory disease.

Avian metapneumovirus (aMPV), also known as turkey rhinotracheitis or swollen head syndrome, causes a variety of disease syndromes in birds, depending on the bird species and virus type.

<span class="mw-page-title-main">Egg drop syndrome</span> Viral disease of birds

Egg drop syndrome '76 is a viral disease that affects birds, notably chickens, ducks, geese and swans. It is characterised by a sudden drop in production of eggs as well as its eggshell quality in apparent healthy laying birds.

<i>Avian metaavulavirus 2</i> Species of virus

Avian metaavulavirus 2, formerly Avian paramyxovirus 2, is a species of virus belonging to the family Paramyxoviridae and genus Metaavulavirus. The virus is a negative strand RNA virus containing a monopartite genome. Avian metaavulavirus 2 is one of nine species belonging to the genus Metaavulavirus. The most common serotype of Avulavirinae is serotype 1, the cause of Newcastle disease (ND). Avian metaavulavirus 2 has been known to cause disease, specifically mild respiratory infections in domestic poultry, including turkeys and chickens, and has many economic effects on egg production and poultry industries. The virus was first isolated from a strain in Yucaipa, California in 1956. Since then, other isolates of the virus have been isolated worldwide.

<span class="mw-page-title-main">History of coronavirus</span> History of the virus group

The history of coronaviruses is an account of the discovery of the diseases caused by coronaviruses and the diseases they cause. It starts with the first report of a new type of upper-respiratory tract disease among chickens in North Dakota, U.S., in 1931. The causative agent was identified as a virus in 1933. By 1936, the disease and the virus were recognised as unique from other viral disease. They became known as infectious bronchitis virus (IBV), but later officially renamed as Avian coronavirus.

<span class="mw-page-title-main">Airsacculitis</span> Bacterial, fungal or viral inflammatory disease of air sacs in birds.

Airsacculitis, also known as air sacculitis, aerosacculitis, air sac disease, air sac infection, air sac syndrome and simply sac disease, is a common inflammatory condition of air sacs that occurs in birds and is caused by various microbial taxa. Having multiple different causative agents, the condition is widely distributed around the world.

References

  1. 1 2 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

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