Poultry Health
Avian Influenza
What is Avian Influenza?
Avian influenza, or "bird flu," is a contagious viral infection. Avian influenza viruses can be broadly classified into two types:
Low Pathogenic Avian Influenza (LPAI): most avian influenza viruses are low pathogenic. These cause little or no signs of illness in birds. It is quite common for wild birds to carry LPAI. A cause for concern is that LPAI strains can mutate within birds (particularly domestic poultry) into highly pathogenic strains, causing severe illness and death.
Highly Pathogenic Avian Influenza (HPAI): viruses can cause severe illness and death in birds.
AI is extremely contagious, which increases the risk and severity of this disease. It can be transmitted between wild birds, domestic poultry and mammals through direct contact, contact with excrement, or airborne transmission in tight spaces.
Since the disease progresses so quickly, the first noticeable sign in your flock is often rapid and unexplained mortality. Other signs of HPAI in poultry can include: respiratory problems (gasping), digestive issues (extreme diarrhea), nervous system symptoms (tremors, twisted necks, pedaling), swelling, and purple discolouration around the head, neck, eyes, and legs. A more detailed list of symptoms can be found below.
This rapid mortality and the associated biosecurity measures (culling, lockdown of the farm, restrictions in the area around the farm) has serious impacts. AI spread damages the economic wellbeing of poultry producers and shakes confidence in the sector at large.
Risk Factors for Outbreaks:
Contact between wild birds and domestic poultry increases the risk of AI transmission and outbreaks. BC domestic poultry is at particularly high risk of contracting AI from wild birds because of the Pacific Flyway migration route.
Transmission between poultry farms also increases the risk of AI outbreaks. The concentration of poultry farms in BC’s Fraser Valley aggravates this risk.
Even small backyard producers have an critical role in preventing AI from proliferating between BC poultry flocks.
Cross-Species Transmission:
AI is primarily introduced to domestic poultry through contact with infected wild birds or other infected domestic poultry (or their excrement, feathers, etc.). Domestic poultry are much more susceptible to severe illness due to AI than wild birds, so any contact between wild birds and domestic poultry poses a serious risk of AI transmission between species.
Increasingly, AI is being transmitted to mammals, including foxes, skunks, cats, marine animals, goats, and cows, as well as sporadically to humans. AI can be transmitted in both directions from poultry or wild birds to mammals as well as from mammals to poultry. In March 2024, avian influenza A(H5N1) was detected in goats and dairy-producing cattle in several US states for the first time. Since then, AI infections in cattle have been increasingly common, as well as in house cats, many of which contracted AI from eating pet food containing raw poultry.
The current strain of avian influenza A(H5N1) circulating in birds in North America poses low risk to the public; however, those who come into contact with sick birds or other animals have an increased risk and should take precautions. Avian influenza could become more serious if the virus develops the ability to spread from person to person.
Impact on Poultry Production and Trade:
AI poses a vital threat to the poultry sector. Since all birds on farms that contract AI generally need to be culled, AI outbreaks have a very serious impact on the farms that contract the disease as well as overall poultry production. Continued spread of AI puts the entire poultry sector at risk because uneducated consumers may become reluctant to purchase poultry and Canada’s trading relationships may be damaged due to fear of AI spread.
Recognizing Signs of Avian Influenza
The most common sign of AI is rapid, widespread mortality in the flock
Other Signs & Symptoms of Avian Influenza
Why Preventing Avian Influenza Outbreaks Matters
Avian Influenza Zoonotic Risks and Public Health
Risk of Avian Influenza Transmission to Humans:
AI spread from animals to humans is uncommon, but a risk that must be considered. It can be spread:
If you touch something contaminated with the virus and touch your eyes, nose, or mouth
If a liquid contaminated with live virus splashes into your eyes (like raw cow’s milk from an infected cow, for example)
If you eat, drink, or inhale droplets contaminated with virus
If you handle sick or dead animals infected with the virus
Public risk of contracting avian influenza is very low. There are no significant food safety concerns because infected birds do not reach the market for human consumption. Infection risk normally only exists for people in direct contact with affected birds.
Safe Handling of Birds:
Do not snuggle or kiss poultry, and ensure that children and visitors do the same.
Wash hands after handling poultry, washing eggs, and working within the Restricted Access Zone.
Cooking and Food Safety Guidelines:
As a producer and distributor, remember that sick birds and eggs from sick birds must be disposed of properly and do not enter the food chain.
Cook all poultry and eggs fully before consumption.
Thoroughly wash hands before handling raw poultry and eggs.
Other Poultry Diseases:
(Click on each disease for details)
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Signs of Marek’s Disease include: death of young birds, inactivity, incoordination, weakness and paralysis of legs and wings, blindness, multiple small tumors on the skin and internal organs
The level of mortality in a flock due to Marek’s Disease depends on the strain of the disease that has infected the flock. In some infected flocks, mortality is quite low.
Although vaccination is not 100% effective in preventing Marek’s disease, buying vaccinated chicks is the most effective way to prevent Marek’s disease. Once a bird is infected, there is no known treatment.
Marek’s Disease cannot be transmitted from poultry to humans.
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Newcastle disease in birds may affect the respiratory, nervous and gastrointestinal systems. Signs may include: decreased egg production, depression, diarrhea, high number of sudden deaths in a flock, respiratory distress.
In humans, the Newcastle disease virus can cause conjunctivitis (pink eye). Such cases occur occasionally in laboratory or farm workers that are not wearing protective eyewear. The risk of contracting this form of disease by the public is minimal, particularly if gloves and protective eyewear are worn to handle sick birds and hands are washed after handling poultry.
Newcastle disease is mainly transmitted by direct contact with diseased or carrier birds. Infected birds may shed the virus in their feces, contaminating the environment. The disease spreads rapidly among birds in close confinement. The virus can also spread unintentionally through the movement of contaminated material, footwear and equipment.
There is no known treatment for Newcastle disease. There is a vaccine available for Newcastle Disease, but it is not readily available for small flocks.
Only two cases of Newcastle Disease have been recorded in Canada since 1973. They were on poultry premises in BC in 2025, so producers must remain vigilant.
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Signs include: runny nose, swollen face and eyelids, pale/discoloured comb, listlessness, weight loss, decreased appetite, ruffled feathers.
Once some birds become infected, mycoplasma will always be present in the flock. Even birds showing no symptoms may carry the infection. Producers can choose to treat birds with antibiotics for symptomatic birds or entirely replace the flock (thoroughly sanitizing between batches).
Mycoplasma infections are not transmissible to humans.
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Signs in poultry include diarrhea, decreased appetite, weight loss, reduced egg production, and in severe cases increased mortality.
Good sanitation practices and the isolation of infected birds is effective in preventing spread.
Coccidiosis cannot be transmitted to humans. The parasite may also impact other livestock and pets, but it is generally a different strain, which does not transmit between species.
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Chickens are generally asymptomatic carriers of Histomoniasis. They can spread the parasite to turkey through manure.
In turkeys, signs include: reduced appetite, drooping wings, listlessness, unkempt feathers, yellow droppings, and death (including acute mortality of 80%-100% in young turkeys).
Raising turkeys on separate pasture from chickens, and keeping turkeys off chicken pasture for several years after the chickens were grazed is the most effective way to prevent blackhead disease. There is no effective vaccine or treatment.
Histomoniasis is not transmissible to humans
