Infectious Laryngotracheitis (ILT)


Infectious Laryngotracheitis (ILT) is an acute respiratory disease in chickens and occasionally, pheasants and peafowl, which often leads to severe losses in the poultry industry as well as backyard flocks. ILT is caused by a herpes virus that usually kills 10-20% of infected birds, although mortality can run as high as 70% in some cases. Egg production in layers also usually drops 10-20%.


Infectious laryngotracheitis (ILT) is a viral respiratory disease caused by herpesvirus. ILT is mainly acute to chronic and affects all birds, though usually those older than 4 weeks. The herpes virus is a cuboidal, enveloped DNA virus. It is an economically significant disease in commercial egg-producing flocks, with an essentially global distribution. In regions where ILT is endemic, the commercial poultry industry is faced with multimillion-dollar losses as a result of mortality, egg production losses, and decreased bird growth.


Signs of infection appear 6 to 12 days after infection and are characterized by mild to severe clinical reactions. The virus is usually shed in respiratory secretions for at least 6–8 days following initial infection. Shedding may continue at a reduced level for as long as 10 days. The virus then may move to nerve ganglia to become a latent (silent) infection, where the virus can remain for months in the bird. Signs include:

  • conjunctivitis, watery eyes and swollen orbital sinuses.
  • coughing, sneezing, extended neck, labored breathing, wheezing and head shaking.
  • bloody exudate on the walls of cages or pens from severe cases.


Control focuses on management practices, emphasizing strict biosecurity. Due to vaccination potential to cause disease, veterinary supervision is strongly recommended when the decision is made to go this route. Since both natural infection and vaccination have been shown to produce "carrier" birds, it is extremely important that susceptible chicken flocks are not exposed to vaccinated or previously infected chickens. Mixing of birds should only be done when a complete history of the birds is available, and it is absolutely certain that a potential ILT "carrier" is not present. Sanitation procedures, which include disinfection of equipment, boots and clothing and proper disposal of litter and carcasses, are essential components of ILT control. Regularly apply adjuvants to enhance natural resistance such as:

Enhances fertility, enlarges eggs and develop sexual organs.

supplementary food in the form of a soluble powder containing beneficial bacteria, vitamins and electrolytes.

herbal-flavored oral supplement solution that contains vitamins, electrolytes, minerals and amino acids. 


There is no vaccines for ILT, however, there are vaccines to prevent secondary bacterial infection. Good biosecurity principles such as effective sanitation and quarantine procedures are important control measures.

Know-How, Poultry