| ||The cause | Signs of the disease | How does ILT spread? | Preventing ILT | Controlling and reporting ILT outbreaks
Infectious laryngotracheitis (ILT) is a viral infection of the respiratory tract (windpipes) of chickens, pheasants and peafowl. It can spread rapidly among birds and causes high death losses in susceptible poultry. Turkeys, ducks and geese do not get the disease, but they can spread the virus. ILT does not affect humans, but people can spread the virus on their clothing or equipment. ILT is a reportable disease in Alberta. Suspected or confirmed outbreaks of ILT must be reported to the Office of the Chief Provincial Veterinarian within 24 hours.
ILT is caused by a herpes virus. It kills the cells lining the airways causing variable degrees of breathing difficulty. Many birds that recover from the acute phase of the disease are potentially infected with the virus for the rest of their life. These carriers shed the causative virus intermittently and are significant sources to infect other birds.
ILT virus (ILTV) dies quickly in the environment. However, it can survive up to 100 days if protected by organic material, such as manure or respiratory secretions. The virus can also survive freezing temperatures. Carrier birds shedding the virus in respiratory secretions are a source of infection. ILTV is killed by common disinfectants, such as iodophores, quaternary ammonium and sodium hypochlorite, but only after organic material is removed from contaminated surfaces.
Signs of the Disease
Affected birds may have difficulty breathing and will cough and gasp. These birds may stand with their wings spread, with their head and neck extended, and struggle for air. Other birds may show milder signs with discharges from their eyes and nostrils. Some affected birds may simply be found dead. Up to 100 per cent of a flock can be affected with up to 70 per cent dying.
Figure 1. Virus can spread between birds.
Infected birds stressed by transportation or other changes in their environment are more likely to develop clinical disease or begin shedding the virus. Farms may remain contaminated for months after outbreaks if they are not adequately cleaned and disinfected.
How Does ILT Spread?
ILT is uncommon in commercial poultry operations in Alberta. However, surveillance is ongoing. When ILT is found, it is often in hobby or fancy flocks. Adequate biosecurity is usually lacking in these flocks as new birds are added to the flock on an ongoing basis from various sources, without isolating the newcomers for several weeks. Some exotic species, such as pheasants and quail, can also carry the virus and spread it within mixed fancy flocks. Many species of wild birds, including crows, sparrows and pigeons, appear resistant to infection with ILTV. Wild birds might act as mechanical vectors for ILTV.
The most important means of spreading ILT is by direct contact between susceptible and infected birds. The virus can also be carried into poultry houses or other farms on contaminated equipment and vehicles, or on dirty footwear and clothing. Humans can be implicated in the spread of infection between farms.
Development and implementation of an effective biosecurity plan is essential to prevent the introduction of viral diseases, including ILT, into a flock. Biosecurity plans must be continually evaluated. Commitment, dedication and persistence by all farm staff and residents are required for success. The essential elements of biosecurity include the following:
Vaccines are available, but are not recommended. Vaccination is not practiced in commercial flocks in Alberta. It is important to realize that vaccination only reduces the risk of disease in exposed birds. It does not prevent infection of vaccinated birds, so they can still be a source of ILTV to susceptible birds for a long period of time. As well, some vaccine strains may be shed from vaccinated birds and cause disease in susceptible unvaccinated contact birds.
- Only purchase birds from a reliable source that is known to be free of ILT and do not add birds to an existing flock.
- Consult a veterinarian quickly to determine the cause of sick or dying birds. Early detection of highly contagious diseases like ILT is essential in minimizing the impact of these diseases on your birds, as well as those of your neighbours.
- Do not allow other people to enter your barns, especially if they have contact with other poultry. Do not visit other poultry farms or barns.
- Provide clean boots and coveralls for anyone who must enter your barns.
- Use a boot dip containing an effective viricidal agent at the entrance of each barn and change the dip daily, even if it looks clean.
- Restrict vehicle traffic on your farm site to specific areas to prevent tracking contamination near or into your barns.
- Do not allow animals (cats, rodents, wild birds) to get into your barns.
- Prevent contamination of feed and water sources by wild birds.
- Store dead carcasses in a closed container until they can be disposed of according to the requirements of the Destruction and Disposal of Dead Animals Regulation. This prevents scavengers from dragging them around and spreading the virus.
- Do not keep fancy birds or poultry on a commercial poultry operation. Employees of commercial farms should not have flocks of poultry or fancy birds of their own at home.
- Perform a thorough cleanout and disinfection between flocks. The ILT virus can survive for a long time in a carcass or manure, especially if frozen. The virus dies quickly when exposed to sunlight or disinfectants.
Controlling and Reporting ILT Outbreaks
The early detection of ILT is essential to minimizing the spread of the disease and its impact on other poultry operations. Any unexplained death losses should be investigated quickly by submitting sick or dead birds to a veterinary diagnostic laboratory for examination. ILT can only be confirmed by post mortem examination and special laboratory tests. Treatment with antibiotics is of no value because ILT is a viral infection. In most situations, early slaughter or depopulation of the flock is the best solution.
Outbreaks of ILT in Alberta must be reported within 24 hours to the Office of the Chief Provincial Veterinarian (OCPV). Poultry boards, hatcheries and feed companies are notified when ILT is diagnosed, without releasing the exact location of the outbreak. This notice serves as a warning to producers and industry to enhance the biosecurity of their flocks and to submit any suspicious losses to a veterinary diagnostic laboratory for examination. Owners of affected birds have a moral and legal obligation to avoid putting other poultry and bird owners at risk of ILT. If you have vaccinated your flock, you should reveal that to anyone you sell the birds to because the vaccine virus can spread to susceptible birds.
Alberta Agriculture and Rural Development has an ILT specific disease response policy to control outbreaks of ILT. This policy is currently under review as part of the regulatory review for the new Animal Health Act, proclamation of which is anticipated in early 2009.
For information about Alberta’s animal health-related legislation, please see the Chief Provincial Veterinarian website.
Dr. Gerald Ollis – Chief Provincial Veterinarian
Alberta Agriculture and Rural Development
Source: Agdex 663-36. Revised June 2008.