Infectious Laryngotracheitis in Chickens: Symptoms, Causes and Vaccination

Gallid herpesvirus 1 (GaHV-1) replicates in the tracheal and laryngeal mucosa, causing severe hemorrhagic necrosis that obstructs the airway with blood and mucus casts.

• Highly virulent field strains: Field ILT virus causes the classic severe hemorrhagic tracheitis. Mortality rates of 10-70% in susceptible flocks are documented. Once introduced to a region, field virus persists in latent carrier birds indefinitely.
• Vaccine-derived strains: Live ILT vaccines (CEO - chicken embryo origin; TCO - tissue culture origin) can revert to virulence after passage through birds and cause outbreak disease. Vaccine-associated field spread of ILT is a recognized problem, particularly with CEO-type vaccines.
• Latent carriers: Recovered birds harbor ILT virus in the trigeminal ganglia as a latent herpesvirus infection for life. Stress can reactivate virus shedding from carrier birds, introducing ILT to new naive flocks.
• Fomite transmission: ILT virus survives on equipment, clothing, and in the environment for days to weeks. Contaminated vehicles and shared equipment are major transmission routes between premises.

The combination of gasping, blood-streaked mucus, and pump-handle breathing in a flock is the classic ILT presentation and warrants immediate diagnosis.

• Tracheal examination: The trachea of a freshly dead bird shows bright red hemorrhagic mucosa with blood and casts of necrotic tissue. This finding is pathognomonic for ILT.
• PCR: Real-time PCR on fresh tracheal swabs or tissue is the fastest and most sensitive confirmatory test. Also differentiates field virus from vaccine-derived strains.
• Virus isolation: On embryonated eggs or cell culture, ILT virus produces characteristic cytopathic effects. Used for subtyping.
• Reportable in some states: ILT is reportable in several US states. Check with your state veterinarian regarding reporting requirements in your area.

There is no specific antiviral treatment for ILT. GaHV-1 is a herpesvirus with no approved poultry antiviral. All management focuses on reducing mortality from secondary infections, airway management, and breaking flock-level transmission.

Emergency airway clearance (individual birds): Birds found dying from tracheal blood cast obstruction may occasionally be saved by immediate intervention. Restrain the bird, open the beak, and carefully remove visible blood casts from the trachea with a small cotton swab or fine forceps. Extend the neck, hold the bird upside down, and swing gently to dislodge deeper material. This is an emergency measure, not a treatment for the viral infection itself, and success depends on the severity of obstruction.

Secondary bacterial infection control: GaHV-1 destroys tracheal epithelium, creating an ideal environment for secondary bacterial pneumonia (E. coli, Mycoplasma, ORT). Broad-spectrum antibiotics significantly reduce mortality from these secondary infections. Oxytetracycline (200-400 mg/gallon for 5-7 days), tylosin (100 mg/gallon for 5 days), or amoxicillin (15 mg/kg twice daily) are standard choices. Begin antibiotic coverage immediately when ILT is suspected, without waiting for lab confirmation.

Emergency vaccination of at-risk birds: Vaccinating unaffected birds in the same facility immediately with ILT eye-drop vaccine can reduce the severity of disease if exposure has not yet occurred. Protection develops over 7-10 days. This strategy works best early in an outbreak when some birds have not yet been exposed. CEO-strain vaccines provide faster protection than TCO but carry higher reversion risk.

Biosecurity lockdown during outbreak: Move no birds, equipment, clothing, or vehicles off the premises during an active ILT outbreak. GaHV-1 spreads readily via fomites and can devastate neighboring unvaccinated flocks. Notify neighboring poultry operations so they can pre-emptively vaccinate.

State reporting: Contact your state veterinarian before taking any actions beyond isolation. ILT is reportable in several US states and some states provide regulatory assistance for outbreak management. Confirm reporting requirements in your state before the need arises.

• Vaccinate in endemic areas using eye-drop ILT vaccine (TCO strain preferred over CEO to minimize vaccine reversion risk). Administer 4-6 weeks before expected exposure or at 2-4 weeks of age in high-risk areas.
• Maintain strict biosecurity. ILT spreads via fomites; disinfect boots, clothing, and equipment between premises. Never allow visitors from premises with ILT history.
• Do not mix birds with unknown ILT history into naive flocks. Recovered latent carriers can reactivate and shed virus when stressed.
• In ILT-free areas, avoid vaccination with live virus, as vaccine virus itself can persist and spread to unvaccinated birds on neighboring premises.