Infectious laryngotracheitis


Infectious laryngotracheitis (ILT) is a highly contagious respiratory disease of chickens caused by a herpesvirus. It can infect pheasants, partridges and peafowl, but does not normally affect turkeys, ducks or wild birds. It is distinct from the herpesviruses that affect parrots and pigeons.

Diagnosis and tests available


Diagnosis is based on a clinical history of a sudden outbreak of significant respiratory disease in chickens, characterised by severe laryngotracheal lesions which can be observed by examination of the larynxes of affected birds.

Tests available


Sample(s) required

Days of the week test is conducted

Turnaround time1

Infectious laryngotracheitis virus real-time PCR2

Fresh tissue or swabs

Accordingly to demand

2-3 working days

Histopathology examination

Fixed tissue

Monday – Friday

Up to 5 days

1 Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.
2 This test is not NATA accredited.

Specimen requirements

Fixed tissue

  • Trachea, larynx, lung
    • As the characteristic histological lesions have a short window of occurrence in the clinical course of disease, they may not always be observed in histopathology.
    • Normal charges apply for any histology undertaken, unless that is the only sample available. In many cases, tracheal histology is not specific.
    • Submit fixed in neutral buffered formalin at a ratio of 10:1 formalin: tissue

Fresh tissue

  • Fresh upper trachea with larynx
  • Up to five larynx-tracheas can be submitted in one container if from same flock/batch and have similar clinical signs and gross findings


  • Tracheal swabs from larynx and proximal trachea should be submitted in viral transport media (PBGS) and with clear labels on bird and tissue sampled.
    • Use sterile swabs
    • Submit chilled
    • Paediatric swabs can be used for small birds
    • As the diagnosis is a flock diagnosis, up to five swabs can be pooled per test sample. Pooling is done at the lab to ensure individual testing can occur if necessary.
  • Dead birds securely packed (i.e double bagged and in a rigid container that is clearly labelled as suspect infectious laryngotracheitis) can be submitted and swabbed at the laboratory. The carcass will be put on hold for further testing pending results.
    • Clinically affected birds should not be submitted live due to risk of contagion
    • A full detailed necropsy, if required, will be charged to submitter


  • Infectious laryngotracheitis is a notifiable endemic disease of poultry
  • Fees for tests undertaken to confirm or exclude a diagnosis of infectious laryngotracheitis are paid by NSW Department of Primary Industries.  Extra testing to establish an alternative diagnosis is at submitters’ expense.
  • Always clearly label specimens as Suspect infectious laryngotracheitis. Pack securely and forward separately from any other specimens.
  • Advise the laboratory Customer Services of your submission and place a warning under the lid of the outer packaging. This will ensure specific biosecurity precautions are undertaken at the laboratory.
  • Strains of ILT vary greatly in their pathogenicity therefore clinical signs can vary from mild upper respiratory tract disease to conjunctivitis, sinusitis, sneezing, coughing, gasping, depression and death. Mortality can vary from a <5 % to >70% in less than a week. Affected birds have reduced egg production.
  • Outbreaks require a source of infection such as proximity to other infected chickens, recent introductions of infected carriers, or possible transmission of virus on material, equipment (including egg trays), vehicles, contaminated litter or feed, personal clothing etc.
  • ILT is not transmitted via the hatching egg.
  • Vaccination of commercial poultry is common. The vaccines are live attenuated strains, carriers are well recognised, and excretion of vaccine virus can occur with other stressors or respiratory diseases. Vaccination may cause mild respiratory signs.