Avian Infectious Laryngotracheitis

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Gallid Herpesvirus 1
Class	DNA Viruses
Order	Caudovirales
Family	Herpesviridae
Genus	Infectious Laryngotracheitis-like Viruses
Species	GHV-1

Also Known As: Infectious Laryngotracheitis — ILT — AILT — Laryngotracheitis Virus — LTV

Caused By: Gallid Herpesvirus I also known as: GHV-1 — Infectious Laryngotracheitis Virus — ILTV — LTV

Introduction

Gallid Herpes virus causes respiratory disease in chickens and pheasants.

Disease varies from mild to peracute, with mortality in peracute outbreaks exceeding 50%.

As with all herpesviruses, GHV-1 can remain latent in carriers after infection and then be shed intermittently, recrudescing with stress.

Signalment

The chicken is the primary host and reservoir host. A form of LT has been described in pheasants.

Distribution

Worldwide. Transmission is via direct contact and contaminated people and equipment. Vermin and wild birds and dogs may aid mechanical transmission.

Clinical Signs

Respiratory signs:

Nasal discharge which is often bloody

Coughing which may also include blood

Sneezing, dyspnoea, gasping, upper respiratory tract pain

Abnormal lung sounds

Decreased egg production, thin egg shells, lack of growth

Neurological and ophthalmologic signs may develop.

Death may occur rapidly and with high mortality in peracute and acute disease. In recent times, LT usually presents in a mild form and most birds recover.

Diagnosis

On post-mortem, haemorrhagic tracheitis and bloodstained mucus are evident. Pneumonia and sacculitis may also be seen. Caseous diptheritic membranes may be present on the mucosae of the upper respiratory tract.

Histopathology reveals loss of cilia, mucosal gland atrophy, intranuclear inclusion bodies and epithelial cell sloughing. Characteristic syncytia develop. A fibrinonecrotic membrane may be present in more chronic disease cases.

Antigen ELISA is both straightforward, quick and sensitive. The PCR can be used to detect LTV.

Immunofluorescent or Immunoperoxidase staining can also be performed and is more rapid but less sensitive.

Virus isolation on a variety of tissues including tracheal swabs or tissue samples may be useful.

Agar Gel Immunodiffusion can detect virus in tracheal samples.

Electron microscopy can be used to demonstrate viral particles in tracheal scrapings or exudates but is insensitive.

Measuring viral antibody measures infection indirectly as serum antibodies peak around 2 weeks after infection and wane slowly afterwards.

Treatment

Where early diagnosis is made, vaccination can be administered in the face of infection to help reduce further morbidity and mortality.

Control

ILT can be effectively controlled by vaccination. Vaccinated and unvaccinated birds should not be mixed due to the possibility of reversion to virulence. Most are modified live isolates and are administered by eye drop.

Adequate biosecurity, quarantine and disinfection is also essential.

Wild birds and vermin should be prevented from accessing poultry and their food/water sources.

Avian Infectious Laryngotracheitis Learning Resources
Flashcards Test your knowledge using flashcard type questions	Gallid Herpesvirus 1 Flashcards

References

Guy, J.S and Garcia, M. (2008) Laryngotracheitis. In: Diseases of Poultry, 12th Edition (eds. Saif, Y.M., Fadly A.M., Glissen J.R., McDougald L.R., Nolan L.K., Swayne D.E.) Wiley-Blackwell, pp 137-152

Jones, R.C. (2007) Infectious Laryngotracheitis. In: Poultry Diseases, 6th Edition (eds. Pattison, M., McMullin, P., Bradbury, J., Alexander, D.) Saunders, Elsevier, pp 258-275

This article was originally sourced from The Animal Health & Production Compendium (AHPC) published online by CABI during the OVAL Project. The datasheet was accessed on 5 June 2011.

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