Infectious laryngotracheitis
Infectious laryngotracheitis (ILT) is a highly contagious viral disease that affects mainly chickens and other fowl-type birds such as peacocks.
The virus causes respiratory signs that can range from mild signs such as conjunctivitis to more severe signs like trouble breathing. In severe cases, the virus attacks the cells of the trachea (windpipe), leading to bleeding within the trachea and coughing up of blood.
There are several strains or ‘classes’ of ILT. Some classes are more severe than others. ILT viruses are known to mutate and reassort with each other, potentially leading to the emergence of more pathogenic or severe strains.
ILT can have significant economic impacts in the poultry industry by causing high mortality, reduced egg production and reduced growth rate.
Birds can recover from ILT infection but then become carriers for life. During stressful events (e.g. start of egg production, transportation or introduction of new birds to the flock), previously infected birds can shed the virus and infect nearby birds.
ILT cannot infect humans and poses no risk to human health.
If you suspect ILT
ILT is a notifiable disease as per The Livestock Disease Control Act 1994. This means that legally you must tell us if you know of or suspect the presence of ILT in any of your birds.
There are 3 ways to notify Agriculture Victoria of notifiable diseases:
- You can call the Emergency Animal Disease Hotline on 1800 675 888 (24 hours a day, every day of the year).
- You can use the Notify Now to send high-quality geo-located photographs of the affected animals, with the owner’s details and property identification code (PIC).
- You can email a completed Disease notification form to cvo.victoria@agriculture.vic.gov.au
Regularly check your birds and immediately report any unusual signs of disease to our staff or your local vet.
How ILT spreads
Infected birds shed large amounts of virus in their respiratory secretions (e.g. coughs and tears) where nearby birds are easily exposed via aerosol transmission. The virus can also survive in dust, clothing, footwear, equipment and hair. This allows spread to occur through the movement of people and equipment between farms.
A large population of recently infected birds can lead to the production of a large plume of virus. The plume of virus can spread to nearby farms, including when birds are transported. It is important to consider truck routes when transporting infected birds, to minimise aerosol transmission of the virus to farms along the route.
Wild bird species such as pigeons and sparrows can carry the virus without showing signs of disease. Therefore, contact between wild birds and poultry flocks should be minimised.
Managing the risk of ILT
Implementation of good farm biosecurity plays an important role in the prevention and control of ILT. Producers and poultry owners should be encouraged to provide on-farm clothing and footwear to employees and visitors. Footbaths and hand-washing stations should be placed at farm entry and in each shed entry.
Movement of visitors and machinery between sheds or farms needs to be controlled and recorded. Birds should be managed by working from the youngest to the oldest flock and from healthy to sick flocks to prevent disease transmission from older or sick birds.
An ‘all in–all out’ flock strategy should be encouraged. Entire farm complexes may need to be emptied at the same time to prevent circulation of the virus between farms in close proximity.
ILT virus can survive for prolonged periods in the environment if protected by organic materials such as manure or litter. The virus is readily deactivated by common disinfectants such as iodophores, quaternary ammonium compounds, formaldehyde and sodium hypochlorite.
Once empty, sheds should be cleaned thoroughly to remove all organic matter such as droppings, dust, mucus and litter. These sheds should then be thoroughly washed with detergent, dried and then disinfected with an appropriate disinfectant before being restocked with new birds.
Vaccination is another management strategy that requires risk-based decision making in consultation with a veterinarian.
Vaccination for ILT
ILT is common enough that vaccination is warranted in all long-lived birds (i.e. birds that reach sexual maturity). In the commercial broiler industry, vaccination of short-lived birds is only warranted in high-risk areas.
Vaccination is not 100% effective at preventing disease but can protect the birds from more severe clinical signs. Good biosecurity must always be used in conjunction with vaccination.
Vaccination should ideally be done via eye drop to ensure each bird receives an adequate protective dose. However, for large farms this may not be practically possible, so drinking water vaccination is conducted instead.
The vaccine is fragile in water, requiring protection from UV light and chlorine and only lasts for a few hours. It is also difficult to manage birds to drink a sufficient dose in this limited timeframe. Some birds may get too high a dose and some none, hence why eyedrop vaccination is preferred if possible.
In the broiler industry, reassessments of the need for vaccination in an area should be conducted periodically. Vaccinating farms for too long may result in an unnecessary increase in production costs, as well as losses due to vaccine reactions. Stopping vaccination too early may lead to a re-emergence of the disease and perpetuation of the cycle of infection.
Currently there are 3 live, attenuated vaccines against ILT on the market in Australia. These can be obtained through veterinary wholesalers or retailers:
- A20 vaccine (Class 1), commonly used in the broiler industry
- SA2 vaccine (Class 1), preferably given via eye drop for long-lived birds
- Nobilis ILT (Class 7), which should not be given with other vaccine classes.
Application of vaccines of different classes in long-lived birds should be avoided, as it might increase risk of virus re-assortment and formation of new dangerous strains.
More information
For more information, see: