Infectious Laryngotracheitis (ILT) is a viral respiratory disease that primarily affects chickens, but has also been found in pheasants, peafowl and turkeys. It is caused by the Gallid herpesvirus type 1, also known as the ILT virus, and is highly contagious. It was first recognised in the United States in 1926 and can cause significant economic losses in the poultry industry.
The incubation period is between two to eight days with a flock developing cases for about two to eight weeks after being exposed to the virus.
Cause
The disease is caused by the Gallid alpha herpesvirus type 1. Cases can be mild or severe with a mortality rate of less than 15%.
Transmission
ILT can be spread through direct contact between birds or through indirect contact with contaminated equipment or surfaces. Infectious Laryngotrachetis is transmitted by the inhalation of droplets from the respiratory secretions of infected birds and via fomites. It enters birds via the upper respiratory tract and ocular route. A high bird density in an area with poor ventalation will see the disease spreading rapidly.
Transmission can be aided by poor biosecurity, especially through the transportation of infected birds, and the spread of contaminated litter.
Clinical signs
The virus primarily affects the upper respiratory tract of chickens, causing inflammation and necrosis of the trachea and larynx. One of the main signs of Infectious Laryngotracheitis is blood-stained mucus. Other signs include gasping, bloody coughs, sneezing, head shaking and lethergy. There can also be a drop in egg laying production with the eggs having thin shells. These signs usually last about 2 weeks and should subside after, although it can last longer in some cases.
Diagnosis
Diagnosis of ILT is based on clinical signs, as well as laboratory testing of swabs taken from the trachea and larynx In the severe form of the disease, blood can be seen in the mucus. In the mild form there are hemorrhagic areas in the upper trachea and larynx, mild conjunctivitis can also be seen.
Confirmation of the disease can be obtained by detection of viral DNA using a virus-specific PCR assays. Histopathology is also used to confirm the disease and antibodies can be detected in blood samples. Supportive care, such as administering antibiotics to prevent secondary bacterial infections and providing supplemental oxygen, may be necessary.
Treatment and control
There is no treatment for Infectious Laryngotracheitis. However, the spread of an outbreak can be reduced if an emergency vaccination is used in the early stages of an infection.
Prevention is the key to controlling ILT. Vaccines are available and are commonly used in commercial poultry flocks. However, the effectiveness of the vaccine can be reduced in the presence of maternal antibodies, which can be passed on from the hen to the chick. Vaccination strategies need to take into account the age of the birds, the level of maternal antibodies, and the risk of exposure to the virus.
In conclusion, ILT is a significant disease of chickens that can cause significant economic losses in the poultry industry. Prevention is key, and good biosecurity practices and vaccination strategies can help to control the disease. If you suspect that your birds may be infected with ILT, it is important to seek veterinary advice promptly.
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