Clinical signs of ILT are variable and virus strain dependant and can include:

• Coughing, gasping and difficulty breathing
• Conjunctivitis including swelling around the eye and discharge from the eye
• Bloody mucous discharge from the mouth (often associated with coughing)
• Nasal discharge
• Elevated flock mortality
• Depressed birds, ruffled feathers.

Post-mortem findings associated with ILT can often be seen in the respiratory tract, including tracheitis and laryngitis, with blood and/or caseous exudate often found associated with each (Figure 1, Figure 2).

ILT is a notifiable disease in NSW which means if you suspect a bird is showing signs of the disease, you must report it. If any bird owner is suspicious of ILT, they should contact a veterinarian or the Emergency Animal Disease Hotline on 1800 675 888 to arrange for sampling and testing.

Notifiable disease testing is conducted by NSW DPI as a cost-free service to the submitter/owner.

As the clinical signs of ILT are variable and can be similar to those observed in a range of other notifiable and endemic avian diseases, diagnosis of ILT must be confirmed by identification of parts of the ILT genome (polymerase chain reaction – PCR). Histopathology of the larynx and trachea can also be used as an adjunct to diagnosis as there are characteristic histological lesions; however, they only occur over a short window of the clinical course of disease. Sampling requirements for ILT testing are summarised in Table 1.

Table 1: Sampling requirements for ILT testing

*Normal histology charges will apply.

For veterinarians needing to submit to EMAI for ILT testing, note the following:

• Place swab samples in transport media (PBGS) or in saline if other media is unavailable. PBGS can be obtained from the following:
• your local LLS District Veterinarian (1300 795 299),
• EMAI (1800 675 623), or
• https://www.dpi.nsw.gov.au/about-us/services/laboratory-services/kits-and-media/order-media.
• Chill swabs and unpreserved tissue samples at either 4°C (refrigerator) or with ice bricks.
• If whole dead birds are being submitted, they should be securely packed (i.e. double bagged and in a rigid container).
• Clearly label specimens and send in appropriate packaging via courier to the NSW APHL:

NSW Animal and Plant Health Laboratories 
Elizabeth Macarthur Agricultural Institute (EMAI) 
Woodbridge Road 
Menangle NSW 2568 
Phone: 1800 675 623

• If you do not routinely dispatch samples to EMAI, contact laboratory customer service (1800 675 623, laboratory.services@dpird.nsw.gov.au) in advance for assistance with dispatch logistics.

For more information on sample submission for ILT testing, visit the NSW DPI Laboratory (EMAI) website.

ILT is endemic in NSW and cases are recorded sporadically in commercial and small-scale poultry flocks.

ILT virus can be easily transmitted by infected birds and contaminated personnel, vehicles and equipment. Transportation of infected birds, inadequate biosecurity, and spread of contaminated litter contribute to the spread of the virus. Contaminated feathers and shed dust can also contribute to airborne spread of the virus. Other important factors to note, include:

• ILT does not normally infect wild birds
• Darkling beetles (litter beetles) can act as a vector for the ILT virus
• ILT virus is not transmitted through the egg and birds are therefore not infected at hatching.

ILT is not a zoonotic agent and thus not of concern to human health.

1-How is ILT controlled?

Biosecurity and vaccination (commercial flocks) are key to controlling ILT. Key steps in biosecurity to protect your flocks from ILT include:

• Source birds from reputable suppliers that are considerate of biosecurity. Remember that chickens can be carriers of ILT for life and stressors, such as transport, can trigger shedding of the virus.
• Isolate new birds or birds returning from shows for a minimum of 14 days before introducing them to other birds in your flock. Remember that ILT and other diseases can be transferred on clothing and equipment so keep them separate during the quarantine period.
• Clean sheds and pens thoroughly when birds are on-site and with enhanced cleaning when there are no birds on site. This gives the opportunity to break the disease cycle.

Vaccination is effective in preventing ILT disease, but it is not without its pitfalls. The ILT vaccines available in Australia are sold in commercial quantities only, typically minimum lot sizes of 1,000 doses, which can make the use of vaccine unfeasible in small-scale poultry flocks. If a small farm has a history of ILT and requires vaccination it may be better to purchase birds from a reputable supplier who vaccinates birds in larger numbers. However, it is important to check that the supplier has vaccinated birds well before the date they are transported (at least 4 weeks) to ensure the birds have good immunity, but also to ensure the vaccine virus has a reduced chance of spread to other birds.

The ILT vaccine virus is a live attenuated virus. The attenuated virus means that it is a more pathogenic strain that has been reduced in virulence. It can still have impacts on bird health, especially if dosed incorrectly or if there is another underlying respiratory illness in your flock at the time of vaccination. Individual eyedrop vaccination is the most effective method but for farms with large bird numbers this may not be practical and vaccination in drinking water may be used.

Keeping ILT out of flocks with good biosecurity is by far the best way to control ILT. Once infected with ILT flock owners may be faced with 2 choices. Firstly, long term control may require euthanasia of all birds, clean the site thoroughly and start with new birds on site. Alternatively, considering its limitations, birds can be vaccinated but it is advisable to vaccinate all birds on site and keep vaccinating (or receive vaccinated birds) for the foreseeable future until there is an opportunity for a rest period and a fresh flock of birds.

2-Additional resources

NSW DPI Laboratory (EMAI) - Infectious laryngotracheitis