Infectious bronchitis

What is infectious bronchitis (IB)?

Infectious bronchitis is an acute, contagious viral disease of chickens of all ages. It can cause severe economic losses to the broiler, breeder and egg layer sectors of the poultry industry.

The causative agent of IB is the infectious bronchitis virus (IBV), an avian gammacoronavirus.

IB is characterised primarily by respiratory signs. Infection with IBV may also lead to kidney problems (nephritis) and problems with egg production and egg quality in laying and breeder hens.

Other closely related avian coronaviruses can also infect game birds and turkeys. For example, in pheasants kidney damage and respiratory problems may be observed. In turkeys the virus can be a cause of intestinal problems.


AHVLA has developed a real-time RT-PCR (RRT-PCR) assay, which is able to detect the presence of IBV viral RNA from a swab or tissue sample. The assay is sensitive, specific and fully validated.

The IBV RRT-PCR assay can demonstrate the presence of IBV and closely related avian coronaviruses within a sample. This enables confirmation of IBV in chickens and/or other avian coronaviruses that can cause disease in game birds and turkeys.

The assay is available in two formats:

  1. For testing individual tissue samples or swabs – TC0787.
  2. For testing pools of up to ten upper respiratory tract swabs – TC0887.

The IBV RRT-PCR test is offered in conjunction with an IBV S1 typing assay for strain identification, again in two formats:

  1. For testing samples submitted as individual tissue/swab samples from one bird or from a group of birds – TC0788.
  2. For testing from one pool of up to ten upper respiratory tract swabs – TC0888.

As such, these tests provide an economic and rapid method for diagnosis. To aid interpretation of results, a full vaccination history should be provided with the samples.

In addition, conventional virus isolation (TC0816) and serology testing (TC0640, TC0912) services for IB are also available.

For differential diagnosis purposes, a fully validated avian metapneumovirus (aMPV) RRT-PCR assay that is capable of simultaneously detecting aMPV subtypes A, B and C is also available – TC0786.

Infectious bronchitis QX

Infectious bronchitis is a well-recognised disease in chickens. However, periodically novel IBV variants emerge. One such group of IB variant viruses that has recently emerged and become widely established across Europe and other parts of the world are the so-called IBV QX strains.

Infection with IBV QX-like strains can cause a range of clinical signs in chickens presenting as respiratory disease and/or nephritis and production losses. In common with other IB viruses, infection of young pullets with IBV QX-like strains can also cause damage to the developing reproductive tract. This can lead to the development of so-called false layer syndrome. Typically in such cases the abdomen of the affected hen is distended. This can cause the bird to adopt a ‘penguin-like’ posture. At post-mortem examination the oviduct looks like a large, thin-walled and fluid-filled sac containing a large volume (commonly 500-1000ml) of clear fluid.

The movement of poultry and fomites are important factors responsible for spread of IBV. The role of other factors such as wild birds is not well understood.

Prevention depends upon maintaining good biosecurity practices and use of IB vaccination schedules as appropriate.

In response to the detection of European IBV QX-like strains in commercial poultry flocks in GB, poultry producers and companies have reviewed IB vaccination programmes. Such changes have been most notable for layer pullets where hatchery spray vaccination of day-old chicks with Massachusetts-type IB vaccine has been introduced, a practice routinely performed in Europe.

Further description of the emergence, clinical features and epidemiology of IBV QX in Great Britain, including in commercial broilers, have been described by Irvine and others, 2010 (Veterinary Record, 167: pages 877-879).  Information can also be found in the 2010 quarterly avian disease surveillance reports.

Further information

Page last modified: 27 December 2012