| | What's being done to protect the poultry industry? | Is Alberta ready in the event of an outbreak of avian influenza? | How many types of AI virus exist? | What are the clinical signs of AI? | How is AI transmitted? | Does AI affect humans? | What agent is responsible for AI and how do you destroy it? | Is AI in Canada? | How is the disease controlled when there is an outbreak? | How can AI be prevented? | Is there a vaccine for AI?
Avian influenza (AI) is a contagious viral disease that affects the respiratory, digestive, and/or nervous systems of many bird species. Although multiple strains of avian influenza virus have been around in wild birds for many years, seldom do these birds show signs of disease due to a natural resistance. Illness or death can occur in domestic chicken and turkey populations if they are exposed to certain strains of the virus.
What's Being Done to Protect the Poultry Industry?
There are eight major steps being taken on the avian influenza front. These include:
- Monitoring for AI virus in commercial poultry and backyard flocks by testing dead birds that could have had avian influenza.
- Working with veterinarians across the province through the Alberta Veterinary Surveillance Network, an early warning system to report and detect animal disease. Poultry surveillance has been accelerated.
- Working with the Canadian Cooperative Wildlife Health Centre and the federal Canadian Food Inspection Agency on wild bird surveillance.
- Implementing an avian influenza prevention program that builds on the work of the Alberta Biosecurity Champions to encourage effective biosecurity practices in our commercial poultry industry and backyard flocks.
- Completion of the Level 3 laboratory in 2006 allows Alberta to conduct advanced work with livestock diseases such as avian influenza.
- Locating the regional diagnostic centre for avian influenza for Alberta, northern British Columbia and the Territories as part of the national laboratory system.
- Having in place a comprehensive response plan in conjunction with the Canadian Food Inspection Agency, Alberta Health and Wellness, Alberta Sustainable Resource Development and our industry in the event avian influenza is discovered.
Is Alberta Ready in the Event of an Outbreak of Avian Influenza?
Governments and industry have worked together for several years to plan and prepare for an outbreak of a disease like avian influenza in the poultry industry. Exercises are conducted regularly to test emergency response plans.
How Many Types of AI Virus Exist?
There are many subtypes of AI virus, designated H1 through H16 along with N1 through N9 (ex: H5N1, H7N3). Also, there are many strains of virus within each subtype. Although this is confusing, it is important to understand that only H5 and H7 subtypes of AI virus have the ability to mutate and become highly pathogenic for chickens. Few strains of AI virus are highly pathogenic. The pathogenicity, or ability of an isolate of AI virus to cause severe disease, is determined in the laboratory under controlled conditions. Strains of the virus that cause severe disease in chickens are called Highly Pathogenic Avian Influenza (HPAI).
What are the Clinical Signs of AI?
Variable degrees of illness are possible in birds because of the differing pathogenicity of the multitude of strains of AI virus. Clinical signs in poultry can vary widely and include:
- no signs of disease at all and quick recovery from the infection
- a few deaths over several days in the flock, followed by an epidemic that kills hundreds or thousands of birds each day
- the onset of depression and droopiness, and/or loss of appetite
- a sudden drop in egg production: many of the eggs are soft-shelled
- a purplish-blue colouring of wattles and combs, with blisters on the combs
- a swelling of the skin under the eyes
- coughing, sneezing and nervous signs
- the onset of diarrhea
- a lack of co-ordination and the inability to stand or walk
How is AI Transmitted?
AI is transmitted when susceptible birds are exposed to viruses excreted from infected birds. Direct or indirect contact with migratory waterfowl is often the origin of infection in domestic poultry flocks. Transmission can also occur through contact with infected poultry, or contaminated poultry products, vehicles, equipment, egg flats, egg cases, clothing and footwear. AI virus is highly concentrated in feces and in nasal and eye discharges. Feed and water contaminated with infected feces are common modes of spread. Biting insects, rodents or farm dogs and cats can also act as mechanical vectors.
Does AI Affect Humans?
In general, AI does not affect humans. However, a few AI strains may infect a small number of humans in direct contact with sick birds. Human-to-human spread of AI virus is rare. An outbreak of influenza in humans, which caused six deaths in Hong Kong in January 1998, was associated with an avian source. Since 2003 outbreaks of HPAI in Southeast Asia have affected over 200 people, all of whom were in close contact with sick poultry, infected bird carcasses or droppings.
What Agent is Responsible for AI and How Do You Destroy it?
AI is caused by a virus belonging to the family Orthomyxoviridae. In general, all influenza viruses are relatively unstable and die readily in the environment if not protected by organic material such as saliva or feces. It is very susceptible to common disinfectants and heat. AI virus can survive for at least 35 days at 4°C in organic matter and up to 23 days in carcasses, if refrigerated. The virus can be isolated from lake water where waterfowl are present. If the water is not treated it can infect confined birds that are drinking the water.
AI virus can survive in poultry meat products, but is destroyed by adequate cooking. There is no danger of humans contracting avian influenza from properly cooked food. Good hygiene practices should always be utilized when handling or preparing food.
Is AI in Canada?
HPAI was identified in Ontario in 1966. In 2004 an outbreak of HPAI (H7N3) in British Columbia resulted in the destruction of millions of domestic poultry at an estimated cost of $300 million. Detection of low pathogenic AI in B.C. in 2005 resulted in the depopulation of poultry on a single farm. A single commercial poultry farm in Saskatchewan was infected with HPAI (H7N3) in 2007 and was depopulated to prevent spread of the disease.
A number of different strains of AI virus are known to exist in wild birds in many parts of Canada.
How is the Disease Controlled When There is an Outbreak?
All H5/H7 strains of AI virus are reportable in Canada under the Health of Animals Act, whether or not they are highly pathogenic. Control or eradication of outbreaks of H5/H7 AI virus is the mandate of the Canadian Food Inspection Agency (CFIA). In an outbreak, CFIA policy dictates the establishment of a “control area” around the infected farm to limit the spread of infection. Infected flocks are destroyed. Producers receive compensation for flocks ordered destroyed, as outlined in federal legislation. These policies are consistent with the recommendations of the World Organization for Animal Health. Movement controls are implemented for poultry, poultry products, people and vehicles. Poultry and eggs at local markets are tested for the presence of antibodies.
How Can AI Be Prevented?
CFIA and the Canadian Customs and Revenue Agency enforce strict regulations on imports of poultry and poultry products from foreign countries. Poultry vehicles and equipment may be inspected and disinfected to ensure they are free from contamination at ports of entry into Canada.
It is impossible to prevent the entry of all AI viruses into Canada because the primary reservoir of the virus is wild birds, especially waterfowl. Implementation of an effective biosecurity plan by individual producers is essential to protecting domestic poultry from AI. Producers and veterinarians must be familiar with the clinical signs associated with AI in order to detect an incursion. Early detection facilitates implementation of measures to minimize spread of the virus and economic damage to the industry.
Producers must prevent direct or indirect contact between domestic poultry and wild birds. Producers should also discourage the presence of wild birds in dugouts and ponds. If dugouts are being used as a source of drinking water, treat the water to kill the virus. Control access to poultry houses and facilities by people and equipment. Make sure poultry equipment is clean and disinfected before it is used, especially if it was used on another farm.
Is There a Vaccine for AI?
Yes, there are vaccines for some strains of AI, but these vaccines do not impart protection for the multitude of other strains that exist. Since there is no way of predicting which strain of AI virus will infect a flock, vaccination is not recommended as a preventative measure, except in the face of an outbreak where the causative strain of AI virus has been identified.
Prepared by:
Office of the Chief Provincial Veterinarian
Alberta Agriculture and Rural Development
Source: Agdex 663-46. Revised November 2008. |
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