Avian Infectious Bronchitis

Also Known As: Infectious Coryza — Infectious Bronchitis — Infectious Proventriculitis — Avian Infectious Nephrosis

Caused By: Avian Infectious Bronchitis Virus also know as: AIBV — ICTV — IBV — AIB — IB

Introduction

Avian Infectious Bronchitis is a highly contagious viral disease primarily of the respiratory system of birds, caused by a coronavirus. The virus can also cause damage to the kidneys and oviducts.

IBV is transmitted mainly by aerosols and also by contaminated people/vehicles/equipment.

It can become latent in a bird and recrudesce with stress, e.g. at point of lay.

This disease is notifiable to the World Organisation for Animal Health (OIE).

Signalment

Chickens, pigeons and pheasants are affected.

Disease is most severe in chicks.

Distribution

Worldwide

Clinical Signs

Reduced weight gain or egg production and reluctance to move is often the first indicator of disease.

Mortality often occurs due to secondary infection, particularly due to E. coli and Mycoplasma infections. Mortality is highest in intensively reared broiler flocks.

Respiratory Signs:

Sneezing, Coughing, Dyspnoea, Ingesta present in respiratory passages, Nasal discharge, Abnormal lung sounds on auscultation

Alimentary and Urinary Signs:

Diarrhoea, dehydration, polydipsia

Polyuria, Pollakiuria

Other Signs:

Reluctance to move

Swelling of the head and face

Conjunctival congestion and increased lacrimation or ocular discharge

Soft egg shells, thin albumin and watery yolks

Neurological signs

Diagnosis

In the acute phase, viral isolation can be attempted from eggs, tracheal swabs or tracheal/lung biopsies.

If more than one week after initial infection, caecal tonsils or cloacal swabs are more reliable.

RT-PCR can be performed on buccal or oropharyngeal swabs but will not differentiate live from dead virus isolate.

Agar Gel Precipitation and Immunofluorescent Antibody (IFAT) tests can also be used to detect the virus.

On post-mortem examination, yellow catarrhal or caseous exudates are present in the trachea, nasal passages, sinuses and air sacs.

On histopathology of the trachea, loss of cilia and sloughing with heterophilic infiltration is evident.

The kidneys are pale and swollen and tubules distended with urates if nephritis is also present. Heterophilic inflammation and degeneration may be evident.

Detection of viral antibodies is also valuable in surveillance, monitoring of vaccination and identification of latently infected birds. This can be performed using Agar Gel Immunodiffusion (AGID) , ELISA, Virus Neutralisation (VN) and Haemagglutination-Inhibition (HI).

RT-PCR, VN and HI can also be used to type IBV isolates.

Treatment

No treatment is available for the viral infection.

Use of antibiotics in drinking water to treat and prevent secondary infection may reduce mortality and losses.

Control

Live and Killed IBV vaccines are available and widely used but cross-protection is poor and numerous serotypes exist so disease is not always prevented. Vaccinations can be administered as intra-muscular injections or sprays. Killed vaccines used alone do not induce immunity and therefore live vaccines are required to prime immunity first.

Good biosecurity and hygiene protocols are imperative to control of this highly contagious disease. Particular efforts should be made with respect to ventilation and air quality.

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References

Animal Health & Production Compendium, Avian Infectious Bronchitis datasheet, accessed 04/06/2011 @ http://www.cabi.org/ahpc/