Infectious Laryngotracheitis is a viral disease and caused by herpes virus. Infectious Laryngotracheitis disease infection caused in respiratory tract. Due to high mortality birds losses egg production and growth. This infection caused all types of birds. Morbidity high and mortality 70% in this disease.

By Sania Tariq,Dr. Muhammad Umair Waqas, Abdul Samad, Areeb Ahmer,Muhammad Hamza, Ayesha Muazzam  and Afeen Javaid


It is caused by DNA virus under the family Herpes viridae and the Subfamily Alpha herpes viridae and currently designed as Gallid herpes virus.

Susceptible Hosts of infectious Laryngotracheitis virus

This disease infect all ages of chickens, but mostly affect older than 3 weeks are more susceptible to infectious Laryngotracheitis virus. Chickens and pheasants are naturally infected. ILT can infect turkeys at about 100 days of age. Heavier breeds are more influenced than light breeds. This disease also occurs in concurrent infection with IB, Fowl pox, ND, Mycoplasma and Haemopillus and deficiency of vitamins or excess ammonia in shed caused this disease.


The infection is transmitted in many ways:

  • The disease is transmitted through ingestion of infected material.
  • Transmission may take place through contaminated feces, litter, equipments, clothes, eggs or chicken handling.
  • Direct transmission (carrier to susceptible bird) of the ILTV has been accepted.
  • The virus can be prolonged in the infected birds.
  • ILTV also caused when birds are stressed such as the time of lay or re-nesting, ILTV was re-activated and spread to susceptible birds.


Incubation period generally ranges from 6 to 12 days after natural exposure.

Mortality varies from 5 to 70% (average 10-20%).

Clinical signs and lesions

There are two signs of infectious Laryngotracheitis virus infection (severe and mild).

Severe form of signs


Bloody mucous

This form can cause high morbidity (state of death) and mortality up to 70%.

Mild form of signs



Drop egg production

Weight gain


Swelling of the infraorbital sinuses (almond shaped eyes) 

Nasal discharge

Gross lesions

Mostly lesions show in larynx and trachea. Severity highly lesions prominent.

Trachea Inflamed (tracheitis).

Blood clots on Trachea.

Dangerous than per acute.

Postmortem lesions

Hemorrhages on trachea, lesions on respiratory tract, infection on airsacculitis, conjunctivitis, swelling on sinuses.

Identification of ILTV

Labs diagnosis is required for ILT, because other disease cause similar clinical signs and lesions, such as IB, ND, avian influenza, infectious coryza, and mycoplasmosis.

ILTV Infection Confirmation Methods 

Isolation method used for infectious Laryngotracheitis virus and DNA detection method also used.

Diagnosis on the basis of postmortem, clinical signs, tests, PCR, Gel diffusion test and FAT (fluorescent antibody technique).

Differential diagnosis

There are some important differential diagnosis:

Differential diagnosis are ND, IB, and CRD (chronic respiratory disease)

How to control?

Some Control measures are:

  • Vaccination
  • Biosecurity


Infectious Laryngotracheitis vaccine are done by live or attenuated vaccine. Some recombinant vector vaccines are also used. Vaccine should be sterile. Vaccination may be to attain by eye drop, drinking water or spray. 


Biosecurity is a crucial method for prevention of ILTV. We should strictly clean dirty clothes, equipments, contaminated material and wet litter. Always use sanitize shed for birds. Be ensure water and feed should be clean.


This disease treated by some antibiotics and vaccines.

Some vaccines are biovac, avipro, cevac LT L, vaxx: on, simune and nobilis are used.

Key points

Infectious Laryngotracheitis is caused by herpes virus and infect mostly young age birds. This disease distribute worldwide and has been recorded from many countries. This infection remove on shed by biosecurity, cleaning and sanitation through. We treated this disease through many live vaccines and antibiotics. This virus recovered almost 10-12 days. This virus killed by sunlight and heat.  This virus morbidity (state of death) rate high but mortality rate low. 

Authors: Sania Tariq, Dr. Muhammad Umair Waqas, Abdul Samad, Areeb Ahmer,Muhammad Hamza, Ayesha Muazzam  and Afeen Javaid Faculty of veterinary and Animal Sciences MNSUAM