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Why has Boehringer Ingelheim entered the ILT vector vaccine market?

Infectious laryngotracheitis (ILT) is a viral disease of chickens caused by the Gallid herpesvirus 1 (GaHV 1), also called avian infectious laryngotracheitis virus. It mainly affects layer pullets worldwide. In addition, it is a growing concern worldwide, especially in broilers at the end of the rearing period. In the broiler segment, mortality resulting from ILT infection has been shown to double every day once clinical signs appear.1 In October 2020, Boehringer Ingelheim Animal Health launched VAXXITEK® HVT+IBD+ILT, the first vaccine to offer protection in one shot from infectious laryngotracheitis, Marek’s disease, and infectious bursal disease (classic and variant types).

What are the main clinical signs and lesions of ILT?

There are two main forms of this respiratory disease described:

  • Acute form: associated with mortality, cough, and hemorrhagic lesions of the trachea as the main lesion reported
  • Sub-acute form: associated with lighter respiratory symptoms and decreased economic performance

In layers, we can see between 0% and 15% drop in egg production with no change in the eggshell quality.

Significant variation can be seen in mortality patterns:


  • Broilers: .7% to 50%
  • Pullets: 1.3% to 16%
  • Layers: 0% to 12%

1. Davison D. Infectious laryngotracheitis. In: Brugère-Picoux J, et al, eds. Manual of Poultry Diseases. Paris, France: French Association for the Advancement of Science; 2013: Chap 22.

What are the transmission paths of ILT?

There are two main transmission paths:2

  • Airborne transmission:
    • Nasal-inhalation
    • Ocular-conjunctiva
    • Oral-ingestion
  • Mechanical transmission (main source):
    • Contaminated equipment
    • Litter
    • Personnel

Airborne transmission between flocks can happen, but the main source is from personnel.

What are the available diagnostic tools to identify ILT in a flock?

  • Postmortem lesions
  • Histopathology of the trachea
    • Degeneration and necrosis of epithelial cells
    • Intranuclear inclusion bodies
    • Hyperplastic non-ciliated epithelial cells
  • Virus isolation
  • Immunofl uorescent antibody test
  • DNA probe (non-isotopic)
  • Immunoperoxidase
  • Electronmicroscopy
  • Enzyme-linked immunosorbent assay (ELISA)
  • Polymerase chain reaction (PCR)

Read the full article in the Poultry International October issue.