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United Kingdom

Infectious Laryngotracheitis

Layer chicken on blue background


Infectious laryngotracheitis (ILT) is an acute, highly contagious infection of chickens caused by a herpesvirus. The route of infection is via the upper respiratory tract and ocular route. Field spread occurs via direct contact from bird to bird, but can also be transmitted by contaminated people or equipment. Transmission between farms can occur by airborne particles or fomites. The virus is highly resistant, but is susceptible to disinfectants.


  • Gasping

  • Coughing

  • Drop in egg production

  • Loss of appetite

  • Inactive birds

  • Increased mortality

Clinical symptoms combined with histopathology, virus isolation or PCR from tracheal swabs.

Currently there is no treatment for ILT. Antibiotics are used to treat secondary bacterial infections if these occur.

Two main ways of ILT prevention are implementation of biosecurity measures and vaccination. Vaccination is carried out using either live attenuated vaccines or viral vector recombinant vaccines. Live vaccines should be applied via eye drop, whereas vector vaccines are administered to individual birds in-ovo or subcutaneously at hatch.