What causes lt in chickens

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Last updated: April 4, 2026

Quick Answer: LT stands for Laryngotracheitis, a highly contagious respiratory disease in chickens caused by the Gallid herpesvirus type 1 (GaHV-1). It primarily affects the upper respiratory tract, leading to severe breathing difficulties and significant economic losses in poultry operations.

Key Facts

Laryngotracheitis (LT) is caused by the Gallid herpesvirus type 1 (GaHV-1).
The virus primarily targets the trachea and larynx, causing inflammation and swelling.
Symptoms include gasping, coughing, sneezing, head shaking, and bloody nasal discharge.
LT can spread rapidly through direct contact, contaminated feed, water, and equipment.
Vaccination is a key strategy for preventing and controlling LT outbreaks in commercial flocks.

What is Infectious Laryngotracheitis (ILT)?

Infectious Laryngotracheitis (ILT), often referred to as LT, is a severe and highly contagious viral disease affecting chickens. It is caused by the Gallid herpesvirus type 1 (GaHV-1), a member of the Alphaherpesvirinae subfamily. This disease primarily targets the upper respiratory tract, specifically the trachea (windpipe) and larynx (voice box), leading to inflammation, swelling, and often, significant respiratory distress.

What are the Causes of Infectious Laryngotracheitis?

The sole causative agent of Infectious Laryngotracheitis is the Gallid herpesvirus type 1 (GaHV-1). This virus is a DNA virus that replicates rapidly within the epithelial cells of the respiratory tract. Once an infection occurs, the virus damages these cells, leading to the characteristic lesions and clinical signs associated with the disease.

How is Infectious Laryngotracheitis Transmitted?

ILT is highly contagious and can spread through various routes:

Direct Contact: Infected birds shed the virus through respiratory secretions (coughing, sneezing). Direct contact with infected birds is the most common mode of transmission.
Indirect Contact: The virus can survive on contaminated surfaces, equipment, clothing, shoes, and vehicles. People or objects moving between infected and susceptible flocks can act as mechanical vectors.
Airborne Spread: While less common over long distances, the virus can spread short distances through the air via respiratory droplets expelled by coughing infected birds.
Fomites: Contaminated feed, water, and bedding can also serve as sources of infection.
Carrier Birds: Recovered birds can sometimes become carriers, shedding the virus intermittently for extended periods, thus posing a continuous risk to susceptible populations.

What are the Symptoms of Infectious Laryngotracheitis?

The clinical signs of LT can vary in severity depending on the virulence of the viral strain, the age and immune status of the birds, and environmental factors. Common symptoms include:

Respiratory Distress: Gasping for air, open-mouth breathing, and noisy breathing (rales).
Coughing and Sneezing: Often forceful, expelling mucus and sometimes blood.
Head Shaking: Birds may shake their heads to clear mucus from their nostrils.
Watery or Bloody Eyes: Conjunctivitis can occur.
Swollen Trachea: Inflammation and swelling of the trachea, sometimes with the presence of caseous (cheesy) exudate or diphtheritic membranes.
Reduced Feed and Water Intake: Leading to decreased growth rates and egg production.
Lethargy: Birds appear depressed and inactive.
Mortality: Can range from mild to severe (up to 30-70% in acute outbreaks).

Diagnosis and Prevention of Infectious Laryngotracheitis

Diagnosing LT typically involves observing clinical signs, post-mortem examination of the trachea, and laboratory tests such as virus isolation, PCR (Polymerase Chain Reaction), or antibody detection (ELISA).

Prevention is crucial due to the rapid spread and economic impact of LT. Key preventive measures include:

Biosecurity: Strict biosecurity protocols are essential. This includes controlling access to the farm, disinfecting vehicles and equipment, and preventing contact between new and existing flocks.
Vaccination: Live and inactivated vaccines are available and widely used in endemic areas. Vaccination programs are typically implemented in young birds to provide immunity before they are exposed to field strains of the virus. The timing and type of vaccine depend on the risk assessment and disease prevalence in the region.
Flock Health Management: Maintaining optimal flock health through good nutrition, ventilation, and stress reduction can help birds better withstand potential infections.
Depopulation and Disinfection: In the event of an outbreak, prompt depopulation of affected flocks, followed by thorough cleaning and disinfection of the premises, is often necessary to eliminate the virus.

It is important to consult with a veterinarian or poultry health specialist for accurate diagnosis and to develop an appropriate disease management and prevention strategy tailored to specific flock conditions.