Infectious Laryngotracheitis (ILTV): Respiratory Pathology & Control
Veterinary manual covering Gallid alphaherpesvirus 1, bloody tracheal cast necropsy, intranuclear inclusions, and CEO/TCO vaccination.
Scientific Overview
Infectious Laryngotracheitis (ILT) is an acute, highly contagious viral respiratory disease of chickens caused by Gallid alphaherpesvirus 1. ILT causes severe economic losses through high mortality (10% to 70%), drops in egg production, gasping, coughing, and coughing up bloody mucus due to severe necrotizing tracheitis.
Etiology & Tracheal Epithelial Latency
Infectious Laryngotracheitis Virus (ILTV) is defined as an enveloped double-stranded DNA alphaherpesvirus (Gallid alphaherpesvirus 1) displaying strict tropism for the respiratory conjunctival and tracheal epithelium.
Like other herpesviruses, ILTV establishes lifelong latent infection in the trigeminal ganglia. Recovered birds remain asymptomatic chronic carriers that shed virus during periods of environmental or production stress.
Clinical Signs & Pathognomonic Necropsy Lesions
Severe (epizootic) ILT outbreaks present dramatic clinical pathology:
- Gasping & Bloody Mucus: Birds extend necks while inhaling (pump-handle respiration) and shake heads to expel bloody tracheal plugs.
- Tracheal Casts: Necropsy reveals severe hemorrhagic tracheitis with lumen occluded by blood clots, fibrinous exudate, or diphtheritic caseous plugs.
- Histopathology: Presence of multinucleated syncytia with characteristic Cowdry Type A intranuclear inclusion bodies in epithelial cells.
Vaccination & Biosecurity Protocols
Control relies on recombinant vector vaccines (HVT-ILT or CVI988-ILT) administered in-ovo or at hatch to avoid vaccine-virus reversion associated with older Chicken Embryo Origin (CEO) vaccines. Audit biosecurity in our Biosecurity Audit Tool.
Differential Diagnosis & Molecular PCR Targets
Differential Diagnosis: Epizootic ILT is differentiated from Newcastle Disease (NDV) and Avian Influenza (HPAI) by the absence of nervous signs or systemic cutaneous hemorrhages. Enzootic ILT is differentiated from Infectious Bronchitis (IBV) and Mycoplasmosis (MG) by histological syncytia with intranuclear inclusions.
Molecular Testing: Real-Time Quantitative PCR targeting the ILTV gC or gE glycoprotein genes provides rapid diagnosis and differentiates field strains from CEO vaccine strains (Mo & Mo, 2025).
All scientific data, diagnostic criteria, and performance benchmarks presented on this page are derived from published peer-reviewed journals and official veterinary codes:
- Avian Pathology & Diagnostics: World Organisation for Animal Health (WOAH, 2023). Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. Paris, France.
- Poultry Diseases & Histology: Swayne, D.E., et al. (2020). Diseases of Poultry (14th ed.). Wiley-Blackwell / American Association of Avian Pathologists.
- Nutrition & Feed Chemistry: Leeson, S. & Summers, J.D. (2001). Commercial Poultry Nutrition (3rd ed.). University Books, Guelph, Ontario.
- Commercial Breed Standards: Aviagen (2024). Ross 308 & Cobb 500 Broiler Performance Objectives. / Lohmann Breeders (2024). Lohmann Brown Management Guide.