POULTRY MED L5: Infectious Laryngotracheitis (ILT)

Infectious Laryngotracheitis

is a highly contagious viral respiratory disease of chickens and pheasants resulting, in the most acute form, in apnea with frequent high mortality, decreased feed conversion and a transient fall in egg production and quality in layers

USA and Australia

The disease is worldwide particularly affecting countries with intensively kept poultry, but has particular importance and is endemic in parts of the __ and __

Gallid herpesvirus-1

ILT is caused by a DNA virus, __ which characteristically causes intranuclear inclusions in the trachea of affected birds and on the chorioallantoic membrane of fertile hens’ eggs

(Iltovirus)

Gallid herpesvirus-1 genus

herpesviruses

ILT virus, like other ___, becomes latent in the affected chicken where it remains for life

stress

Under conditions of ___, the virus may be reactivated

infectious bronchitis virus or Newcastle disease virus

The virus appears to spread more slowly than other respiratory viruses such as __ or __

egg

The virus is not ___ transmitted

Chickens

are considered the primary host of GaHV‐1

Bird to bird

___ transmission is necessary to maintain the virus circulating among susceptible populations. Live transport of infected broilers has been associated with the spread of the disease as infected chickens most‐likely release virus on fomites during transportation

Indirect

__ transmission of the virus constitutes a significant mode for spreading the infection. Exposure to contaminated equipment, personnel, contaminated litter, manure, and infected carcasses are the main modes to spread the diseas

6 to 14

The incubation period of the disease can be wide‐ranging, since it is contingent on the viral dose, route of inoculation, degree of viral virulence, and bird age. Based on field observations clinical signs of the disease commonly appear between ___ days post exposure

older

ILT is more commonly seen in ___ birds and may be present in acute or mild forms

acute

In the __ form, between 5–10 days after exposure, disease is characterized by rattling, coughing and extreme difficulty in breathing, with some birds dying through asphyxiation.

neck extension

The effort of clearing tracheal obstruction by ___ causes blood and caseous material to be coughed up which stains the feathers, litter and walls of the house

pathognomonic

Expectoration of blood is not found with any other respiratory disease of poultry and is __ and may be sufficient for a positive diagnosis

acute

The __- form is likely to be accompanied by high mortality, sometimes exceeding 50%

mild

In the __ form, birds may show respiratory signs similar to other generally milder respiratory diseases such as infectious bronchitis, low virulence Newcastle disease or mycoplasma infection. There may be coughing, head shaking, lacrimation and general depression.

14

Respiratory signs usually subside by __ days of onset, though some individuals may show signs for longer, particularly if other respiratory pathogens are present.

oviduct

In laying flocks, there may be a transient loss of production and egg quality with a return to normal when the disease has subsided. No apparent effect on __ unlike IB.

respiratory

The virus appears to be a pathogen principally of the __ tract

trigeminal ganglia

Birds that have recovered will carry latent virus throughout life in the ___

Reactivated

___ virus may not result in disease in the latently infected individuals but can cause disease after contact with previously unexposed birds

acute

Severe lacrimation seen on ___ form

mild

Moderate lacrimation seen on __ form

acute

Caseous material blocking the tracheal airway in ___ form

expectoration of blood and caseous material

An acute respiratory disease, often with significant mortality accompanied by the __ and __, is pathognomonic for acute ILT

mild

In flocks with __ ILT, where disease is moderate, laboratory methods will be required to demonstrate the virus and confirm the diagnosis

Cowdry-Type A

Examination of epithelial cells in trachea during first few days of infection to detect blue stained ___ intranuclear inclusion bodies (H&E stain)

1. Examination of epithelial cells in trachea

2. Negative Staining via Electron Microscopy

3. PCR (RT-PCR, rRT-PCR)

3 diagnostics for ILT

PCR (RT-PCR, rRT-PCR)

modern standard diagnostic for ILT

True

T or F: No other respiratory disease in poultry shows such dramatic signs

vaccination

Control of ILT generally involves routine __ of broiler‐breeders, layers, and vaccination of broilers if necessary, while implementing biosecurity

True

T or F: “Infectious laryngotracheitis is a community disease and if your neighbor has it, you may get it”

1. Live attenuated vaccines

2. Recombinant vaccines

2 categories available

True

T or F: No drug has been shown to be effective in reducing the severity of lesions or relieving clinical signs

real‐time PCR and histopathology

The use of __ and __ are most commonly used to confirm infection.

alone or in combination

Both attenuated vaccines and recombinant viral vectored vaccines can be used __ or in __