Infectious Laryngotracheitis

Last week a Bitchin’ Chickens follower asked me for details about sending two hens for a necropsy at the provincial Animal Health Centre. I gave her the information and asked if she would share the necropsy results when she got them. The Avian Pathologist initially gave her a tentative diagnosis of Infectious Laryngotracheitis while they were awaiting the lab results. I perked a bit because I hadn’t done a post on ILT and was hoping to write a case study. The final diagnosis came back positive for Infectious Coryza, but by then I had started to do research on ILT.

The virus was first identified in Canada in 1925 and was the first major avian viral disease to have a vaccine.

Like, Coryza, ILT is a highly contagious upper respiratory tract disease in chickens caused by the ILT virus (ILTV), also known as Gallid herpesvirus 1. The incubation period after exposure is 6-12 days, during which time it replicates in the mucous membranes of the eyes and trachea. The lining of the larynx and trachea are always affected, while the respiratory sinuses, air sacs and lung tissues may or may not be.

Symptoms

Mild Form:

• Mild to moderate tracheitis, sinusitis, watery eyes, nasal discharge
• 5% morbidity and 2% mortality

Severe form:

• Coughing bloody mucous
• Rattling
• Gasping
• Neck stretching
• Head shaking
• Sneezing
• Conjunctivitis  (inflammation of the mucous membranes around the eye)
• Reduced egg production
• Lethargy
• Symptoms usually decrease after 2 weeks
• Mortality ranges from 5% – 70%

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Transmission

• Introducing new chickens to the flock (either who have received the vaccine, are actively infected or recovered carriers).
• Birds will shed the virus in their poop for up to two weeks after being vaccinated.
• Vaccinated and recovered chickens will only shed the virus in their poop when subjected to stress (e.g. often at the onset of laying or when adding to the flock).
• Actively infected chickens will transmit the virus mainly through coughing or sneezing.
• Indirect transmission between farms through contaminated people (hands, clothing, footwear) or fomites (transport cages, waterers, feeders).
• The virus can live for 8-10 days in poop and lasts longer in cooler weather.
• ILTV may survive for up to 80 days on non-conductive material (i.e. wood) if not disturbed.
• Can be killed by sunlight, heat and drying.
• ILTV is carried by infected birds for life and gets reactivated when birds are stressed, so consider keeping a closed flock.

Treatment

• There is no effective treatment
• Antibiotics may be given for secondary bacterial infections

Prevention

• Obtain stock from known ILT-free flocks
• Practice good biosecurity and quarantine
• Disinfect feeders, waterers, crates
• Recognize symptoms and isolate sick birds immediately

Credits: Indian Veterinary Research Institute; Merck Veterinary Manual; Poultry DVM; Zoetis. Featured Photo: Merck Veterinary Manual