Source: International Federation of Animal Health

Q: What is Avian Influenza?

A: Avian Influenza is a respiratory disease of birds caused by a virus which occurs in low pathogenic and high pathogenic varieties. Outbreaks of low pathogenic Avian Influenza (LPAI) are common around the world, and are generally easily controlled, whereas the highly pathogenic versions of Avian Influenza (HPAI) are more serious due to the very high mortality rate in affected birds.

The current variant of highly pathogenic Avian Influenza now present in Asia, the Middle East and parts of Africa and Europe is the H5N1 strain. The name “H5N1” refers to the arrangement of proteins on the surface of the virus where “H” refers to the hemagglutinin protein and “N” to the neuraminidase protein. An Avian Influenza virus is identified by the presence of a combination of H and N subtypes of which there are sixteen H subtypes (H1-H16) and nine N subtypes (N1-N9).

Avian Influenza is most common in wild waterfowl species, but has also been reported in many common species of poultry, including chickens, ducks, turkeys, geese, pheasants and quail, as well as in a variety of other birds like parrots, cockatoos, and parakeets. Some species are more resistant to infection or can be asymptomatic transmitters of the disease.

Q: How is Avian Influenza spread?

A: Avian Influenza is primarily spread by direct contact between healthy and infected birds, or through indirect contact with contaminated equipment or other materials. The virus is present in the feces of infected birds and in secretions from their noses, mouth and eyes. The virus can spread into domestic flocks kept outdoors through fecal contamination from wild birds, whereas infection among indoor flocks is spread via airborne secretions and feces. The spreading of the virus through feces and secretions is often referred to as the “shedding” of the virus.

Q: What happens when Avian Influenza is detected or suspected in a bird or flock?

A: Highly Pathogenic Avian Influenza (HPAI) is a reportable disease by the World Organization for Animal Health (OIE). OIE has developed animal health standards classifying the highly pathogenic strains as reportable diseases. Any outbreak should be immediately reported to local and national animal health authorities.

Q: What can be done to prevent Avian Influenza?

A: There is no single solution to prevent Avian Influenza, but there are three types of measures that are used in conjunction with each other. Firstly, biosecurity and surveillance measures must be introduced, these include:

• the quarantine of infected farms;
• the restriction of movement of poultry in areas surrounding confirmed or suspected infections;
• implementation of stringent hygiene measures such as using protective clothing and disinfecting vehicles passing through infected areas to prevent the spread of the virus through contaminated clothes or equipment;
• surveillance of wild birds and domestic poultry in areas surrounding confirmed or suspected infections.

Secondly, “stamping out” or culling of infected birds is also used to prevent the virus from spreading;

• All birds in a specified location (e.g. a farm) must be culled.
• The carcasses of culled birds must be appropriately disposed of; this is usually done via burial or burning.
• Birds in specified zones surrounding an outbreak may also be culled.

Thirdly, to prevent further spread of the infection, a vaccination program may be implemented taking the following into account:

• Vaccination is a prevention strategy,
• Vaccination does not always prevent infection, but the vaccinated bird does not become ill and die as unvaccinated infected birds do.
• If a vaccinated bird becomes infected, it either does not excrete (“shed”) the virus or sheds much lower levels of virus than an infected unvaccinated bird and subsequently stops shedding the virus.

Q: What can be done to cure an infected bird of Avian Influenza?

A: There is currently no cure for highly pathogenic Avian Influenza. Current practice in most regions of the world requires the culling of infected birds, not treatment, hence prevention is extremely important.

Q: What is the risk of mammals such as cats being infected by H5N1?

A: Experience in Asia during 2003 and 2004 shows that domestic cats are at risk of infection, sometimes fatal infection of the H5N1 virus. It is therefore advisable to avoid contact between cats and wild birds or poultry in infected areas. There is no evidence of any transmission of the H5N1 form of Avian Influenza from cats to humans.

For more information on H5N1 mammal infection, please see WHO statement of February 28, 2006: www.who.int/csr/don/2006_02_28a/en/index.html

Q: Does Avian Influenza present a risk to human health?

A: Firstly, it is important to note that all reported human cases of H5N1 Avian Influenza have occurred in people who have had close, direct contact with infected birds. So far there is no evidence of any human to human transmission of the H5N1 virus.

For information on diagnosis and treatment of humans infected with Avian Influenza, see:
www.who.int/csr/disease/avian_influenza/guidelinestopics/en/index1.html

For details of human cases of Avian Influenza see: www.europa.eu.int./comm/health/ph_threats/com/Influenza/ai_human_en.htm

Q: Does the spread of H5N1 strain of Avian Influenza threaten the safety of the food supply?

A: First, the chance of infected poultry entering the food supply is extremely low. Secondly, in the unlikely event that contaminated poultry products reaches the food supply stage, the level of virus would be extremely low and present no danger of infection provided that the food is properly cooked.

Q: Is it true that large commercial poultry operations facilitate the spread of the disease?

A: No, in fact just the opposite is true. Large commercial poultry operations, which raise birds indoors, use biosecurity measures designed to keep birds as disease-free as possible. Many of these safeguards are not available to producers when flocks are raised outdoors.

AVIAN INFLUENZA VACCINATION

Q: Are vaccines available to minimize the risk of infection with the H5N1 form of Avian Influenza?

A: No, there are presently no vaccines licensed for use in Canada that minimize the infection of H5N1 Avian Influenza in poultry. The Canadian Food Inspection Agency, however, can authorize the use of unlicensed vaccines and biological products in the event of an outbreak. Arrangements are being made with manufacturers to have a quantity of these products available for emergency preparedness. (If applied, vaccination would only be one element of a containment strategy which would involve the containment and/or depopulation of poultry in specific zones.)

Q: How are vaccines used?

A: Entire flocks must be vaccinated and this is done by injection. Birds begin to build up immunity immediately after vaccination and after around 3 weeks their immunity is fully established. To increase the duration of the immune protection, it is necessary to re-vaccinate after the initial vaccination.

Q: What is the outcome of vaccination?

A: Vaccinated healthy birds need a greater amount of virus to be infected, but it is possible for some to become infected and excrete the virus (sometimes referred to as “shedding” of the virus) although most vaccinated birds are protected from infection and do not shed any virus. However infected vaccinated birds that shed the virus shed it at such a low level that it is insufficient to infect other birds. Scientific studies show that 2-3 weeks after vaccination, transmission of the virus is completely stopped.

Experience has shown that vaccination of birds - in combination with stamping out, biosecurity and surveillance measures - can be an effective additional tool for preventing viruses from spreading during the outbreak stage. Vaccination is particularly useful in areas with high poultry density. The outcome of vaccination is that vaccinated birds do not become sick and die and the spread of the virus is dramatically reduced or stopped.

Q: Is vaccination alone the solution to stopping the spread of Avian Influenza?

A: No, vaccination alone is not the total answer. While vaccination effectively protects treated birds and limits the spread of the disease thus assisting in eradication programs, it is a preventative measure which cannot be used when birds are already infected. The best use of the vaccine is as a component of an eradication program under the control of animal health authorities alongside other measures such as surveillance, biosecurity and stamping out.

Q: Who decides whether or not to vaccinate in the event of an Avian Influenza outbreak?

A: The decision to vaccinate is made by the relevant authorities of individual countries, taking account of local conditions and the prevailing epidemiological situation. In Canada, the Canadian Food Inspection Agency has the authority to decide if it is beneficial to vaccinate.

Q: Is it safe to eat the meat and eggs from vaccinated poultry?

A: Yes. Meat and eggs from healthy vaccinated poultry pose no human health threat.

THE ROLE OF THE ANIMAL HEALTH INDUSTRY IN AVIAN INFLUENZA

Q: What is the animal health industry's contribution to the combating Avian Influenza?

A: A number of animal health companies produce H5 vaccines protecting against H5N1 that are effective in preventing clinical disease in birds. These vaccines help control the spread of Avian Influenza by increasing the resistance of the vaccinated bird and by reducing shedding of the virus by infected birds.

Animal health companies also contribute to the control efforts of Avian Influenza with their wealth of knowledge in the field and manufacture products to control disease vectors.

Q: Can the animal health industry supply enough Avian Influenza vaccines?

A: Up until now, the companies making Avian Influenza vaccines (in applicable countries) have been able to meet demand for their products.

Vaccine production is a complicated process. The production and testing takes at least four months, including all controls on quality, safety and efficacy of the product. Animal health companies need advance warning of a country's intention to implement vaccination in order to be able to supply the requisite amount of vaccines.