Infectious laryngotracheitis (ILT)

Infectious laryngotracheitis (ILT) is an extremely contagious virus that affects chickens and other fowl-type birds such as turkeys and peacocks.

The virus attacks the cells of the trachea (windpipe), leading to bleeding within the trachea and the bird has difficulty breathing. Birds can die of asphyxiation when the disease is severe enough.

ILT is a nationally notifiable disease where disease suspicion in South Australia must be notified to PIRSA under the Livestock Act 1997.

ILT is endemic in Australia and the virus is commonly present in long-lived birds such as egg-laying chickens. The severity of disease after infection is variable depending on the age of birds, and birds can develop natural immunity after infection. However, once birds are infected they become carriers for life and can shed the virus during periods of stress, posing a risk to young, naïve birds.

Commercial farms at risk of ILT infection routinely vaccinate their birds to minimise disease (and therefore losses) from occurring in the first place. See our vaccinations and antibiotics for poultry page for more information.

How infectious laryngotracheitis (ILT) spreads

The virus survives well in the environment, particularly in cool, wet conditions, and is easily transmissible through physical contact or aerosol (small droplets in the breath). Aerosol spread only occurs from infected birds who are coughing large volumes of the virus into the air.

With a large population of infected birds producing a large plume of virus (e.g. when transporting infected birds on live-haul vehicles) and favourable environmental conditions, ILT can travel up to 2 kilometres to infect other birds. It is therefore important to consider which routes trucks should take when:

  • moving uninfected birds - to minimise becoming infected from nearby infected farms
  • moving infected birds - to minimise infecting nearby uninfected farms.

Spread of the virus via physical contact occurs mostly due to people movement and equipment. People on an infected farm can have their clothing contaminated with the virus, and they therefore pose a risk to birds on an uninfected farm.

Wild bird species such as pigeons and waterfowl, are able to carry the virus without showing signs of disease. Therefore contact between wild birds and poultry flocks should be minimised as much as possible.

Infectious laryngotracheitis is not a human health risk.

ILT in South Australia

An outbreak of ILT was declared in SA since September 2018.

From this time to June 2019 there have been more than 60 notifications of ILT mainly affecting commercial broiler farms and all were the Class 7 ILT virus type. Over 30 of these notifications were re-infections i.e. the same farms became re-infected with new batches of birds.

ILT interstate

New South Wales (NSW) and Victoria have historically had greater incidence of ILT disease than SA. These states have also experienced more virulent Classes of the ILT virus (Classes 8, 9 and 10), which occurred from mutation of the Class 7 virus. This is another reason why movements of birds from interstate must be carefully managed.

Reduce the risk of ILT on your farm

Please contact your local veterinarian or phone the Animal Disease Hotline immediately on 1800 675 888 if your birds are showing any signs of difficulty breathing.

Please contact Biosecurity SA if you need to move birds within SA. Biosecurity SA can advise on which truck routes to take to minimise ILT infection risk.

Biosecurity SA sends email alerts whenever ILT is suspected in a particular town. You can subscribe to this email list by contacting Biosecurity SA .

Vaccination for ILT

To prevent disease from occurring, pullet farms that rear birds for commercial egg-production routinely vaccinate all birds against ILT.

This is best done by eye-drop vaccination to ensure that all birds receive the appropriate dose (as opposed to water vaccination). Biosecurity SA strongly recommends the use of A20 or SA2 vaccines (Class 1 ILT virus type) due to the possible nature of the Nobilis ILT vaccine (Class 7 ILT virus type) to become associated with a disease outbreak and mutation.

It is difficult to vaccinate commercial broiler farms adequately for several reasons, including:

  • the impossibility of performing eye-drop vaccination for all birds due to the large number of birds present on farms, therefore vaccination must be done in-water
  • the fragility of the vaccine in the water, requiring protection from UV light and chlorine and at best lasting for only 4 hours in the water
  • managing birds so that they drink all of the water within those 4 hours but not too quickly that some get too high a dose and others none.

Therefore, despite industry attempts to vaccinate, this does not provide full coverage to the birds. Good biosecurity is the main tool to eradicate the disease.

For more information please see our vaccinations and antibiotics for poultry page.

More information


Biosecurity SA
Phone: (08) 8207 7900

Page Last Reviewed: 24 Jun 2019
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