Overview

Infectious laryngotracheitis (ILT) is a contagious disease of poultry caused by Gallid herpesvirus 1 (GaHV-1). The most affected species are:

  • chickens
  • pheasants
  • pheasant mixes
  • partridge
  • peafowl

Turkeys, waterfowl and guineas can be carriers. Losses occur due to increased morbidity and mortality, decreased growth rates and egg production.

Human or mammal transmission

There is no evidence to suggest that GaHV-1 is transmissible to humans or other mammals, meaning there are no food safety issues if consuming meat and eggs from ILT-infected birds. ILT infects chickens of all ages at all production stages from 3 weeks old to adulthood stage.

Disease classification

ILT is listed as an immediately notifiable disease under the federal Health of Animals Act by the Canadian Food Inspection Agency (CFIA). It is also listed as an immediately notifiable hazard under the provincial Ontario Animal Health Act, 2009.

Prevention and rapid detection

Major trading partners consider ILT a top tier notifiable disease. This reminds industry of the importance of prevention, rapid detection and effective containment to limit the potential for further spread and minimize the negative impacts of this disease. It is strongly recommended that producers work with their poultry veterinarian on diagnosis, prevention and vaccination strategies.

ILT can spread through poultry flocks via direct transmission, such as:

  • mixing birds from various sources, especially in small flocks
  • airborne transmission
  • using attenuated vaccines (rolling reaction) or poor vaccine administration technique

It can also be spread indirectly through:

  • wild birds
  • domestic animals
  • rodents and insects (flies, darkling beetles)
  • people wearing contaminated boots or clothing, or having contaminated hands
  • contaminated objects, such as:
    • vehicles
    • bedding
    • cages
    • feathers
    • carcasses

Clinical signs

The incubation period for ILT is 6 to 12 days. A range of 5% to 80% of the flock may become sick and infected birds usually die. Some birds recover within 7 to 10 days but remain carriers for life. Flock mortality can climb as high as 20% and the disease may persist in the flock for a period of 2 to 6 weeks.

Clinical signs include:

  • difficulty or very loud breathing
  • stretching head and neck while breathing
  • head shaking (to expel mucus and blood from the respiratory tract)
  • blood spots on the beak and feathers, red and watery eyes
  • decreased feed and water consumption
  • decreased egg production
  • birds crowding together, being less active, and having tousled feathers

Diagnostic criteria

Any 1 of the following criteria will be diagnosed as a suspect case, while any 2 of the following criteria will be diagnosed as a confirmed case:

  • histological lesions (intranuclear inclusion bodies)
  • clinical signs
  • positive (PCR) test

Characteristic post-mortem findings and epidemiological links are also considered.

Disease control

Biosecurity

  • Do not expose susceptible chicken flocks to previously infected chickens.
  • Mixing of birds should only be done when a complete history of the birds is available, and it is certain that a potential ILT "carrier" is not present.
  • Maintain sanitation procedures by disinfection of equipment, boots and clothing and proper disposal of litter and carcasses.
  • Discuss how to implement a suitable vaccine protocol for your flock with your veterinarian.

Animal health laboratory submissions

Submission of samples to the animal health laboratory for testing should be representative of your flock. If you are not familiar with the type of samples that need to be submitted, ask your veterinarian.

The submission form should include:

  • type of operation
  • number of birds at risk
  • number of birds affected and the vaccination history

Submit tissues from separate birds in tightly sealed and labelled Whirl-Pak bags for rapid distribution to the designated laboratory sections. For histology, use formalin fixed sections of trachea, larynx and bronchioles. For isolation of ILT virus, trachea and lung are required.