Infectious Laryngotracheitis (ILT)

Infectious Laryngotracheitis (ILT) is a herpesvirus infection of chickens, pheasants, peafowl and turkeys. The effects of this disease are largely commercial as it can cause deaths and affects productivity.

How is ILT spread?

Pathogenicity can vary with morbidity of 50-100 per cent and mortality usually 10-20 per cent but sometimes up to 70 per cent.  Transmission between farms may occur by airborne particles or fomites.  The virus is highly resistant outside the host but is susceptible to disinfectants. Movement and mixing of stock and reaching point of lay are predisposing factors.

ILT is a notifiable disease.

Implications for human health and food safety

There are no human health or food safety implications associated with ILT.

Signs in poultry

  • dyspnoea
  • gasping
  • coughing of mucus and blood
  • drop in egg production
  • ocular discharge
  • sinusitis
  • nasal discharge (low pathogenicity strains)
  • post-mortem lesions (Severe laryngotracheitis, often with blood in lumen; caseous plugs may be present)


There is no treatment but antibiotics can be used to control secondary bacterial infection if this is marked.


Methods of prevention include strict biosecurity, quarantine or all-in/all-out operation. In the event of an outbreak vaccination of poultry over 4 weeks of age on affected sites would be considered on a case by case basis. Importation of vaccine and the use of vaccine is controlled by DAERA.  Susceptible stock should be kept separate from vaccinated or recovered birds. Strict biosecurity should also be applied when moving equipment or materials between these categories of stock.  

Farmers are asked to contact their Private Veterinary Practitioner (PVP) if they suspect that their flock has been infected.

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