Avian Influenza: How Avian Flu Affects Domestic and Wild Flocks, and Why a One Health Approach Is Important

A strain of the bird flu virus is spreading in domestic poultry flocks in Canada but poses no risk to humans at this time.

The bird flu virus, commonly known as bird flu, is a contagious type A flu virus that can infect and kill poultry (such as chickens, turkeys, pheasants, quail, domestic ducks, geese, and guinea fowl) and wild birds (including migratory birds). †

There are at least 16 types of avian influenza viruses, which are classified by a combination of two groups of proteins: hemagglutinin or HA and neuraminidase or NA. This is where the H and N in bird flu strains come from: they identify specific HA and NA proteins, such as the current H5N1 strain causing outbreaks in Europe, the United States and Canada†

Types of avian influenza viruses are further classified as highly pathogenic (HPAI) or low pathogenic (LPAI). HPAI viruses — including the current strain of H5N1 — are extremely contagious, can cause serious illness and high mortality (90-100 percent) in domestic poultry and spreads quickly from herd to herd.

Bird flu: where is it?

Pathogenicity (the ability to cause disease) is defined in relation to disease severity in domestic poultry. Still, the reach of bird flu is not limited to this population. H5N1 is spreading in wild bird populations around the world. Since October 2021, significant outbreaks have been detected in Asia, Africa and Europe†

H5N1 is of immediate national importance in Canada as migratory birds flock to our shores. The Eurasian strain of H5N1 was detected in Newfoundland in December 2021 and in hunted wild birds in the eastern US in January 2022. Between December 2021 and May 2022, this virus was found in eight Canadian provinces and 35 US States†

Bird flu and animal health

Wild birds can be infected with highly pathogenic bird flu and show no signs of disease. They can bring the disease to new areas when they migrate, exposing domestic poultry to the virus.

One infected bird may show signs including coughing, gasping for air, swelling of the head and diarrhea. Because flu viruses in birds can multiply in tissues outside the respiratory system, infected birds may also exhibit neurological symptoms, including paralysis and tremor.

Once infected, death in some bird species is almost inevitable, within 24-72 hours. The first sign of infection can sometimes be mass death.

The consequences of outbreaks are carried by individual farmers and are felt throughout the agricultural sector. Where outbreaks occur, it is often the policy to clean up all poultry, infected or healthy, to prevent the spread of the virus. This represents heavy economic losses for farmersthat can have a long-term impact on their livelihoods and well-being.

Of course, the bird flu virus doesn’t differentiate between farm and field; it can decimate wild bird populations, in addition to farmed flocks, and there have been reports of mass deaths in the UK and Israel in 2021 and 2022† In addition to disrupting the local ecology, which often includes finely calibrated food webs, such outbreaks occur at the expense of biodiversity.

Avian Influenza Virus and Environmental Health

The effects of climate change on the ecology of disease are impossible to ignore. Migratory birds – especially waterfowl – are a natural reservoir for the bird flu virus† As birds migrate and mingle with other individuals and flocks, viruses “float” and “shift” meaning viral genetic material can change in unexpected ways.

In the context of bird flu and climate changewhere migratory routes and seasons change, previously segregated migratory bird populations now meet, increasing the likelihood that new virus variants will emerge.

Avian Influenza Virus and Human Health

Several subtypes of avian influenza, including the H5 subtype, they have been shown to interbreed species and travel from birds to mammals – including dogs, cats, pigs and humans† It is important to note that these events are rare and that: avian influenza virus currently poses no health risk to humans†

Although close to 880 human infections and more than 450 deaths have been attributed to earlier strains of H5N1, only two cases are known of: human infection with the current circulating strain† However, there is concern that, through mutations and genetic exchanges, the H5N1 avian influenza virus may gain the ability to pass from birds to humans and possibly from humans to humans.

Because of the potential of avian flu to spread rapidly through an animal population, a robust surveillance program to monitor the evolution and diversity of avian flu viruses for preventive action is an essential public health measure.

Bird flu virus and One Health

Avian flu virus management and control requires a One health approachwhich attaches equal importance to measures that tackle the avian flu virus from the point of view of animal, human and environmental health.

Climate change, human population growth and socio-economic factors have long-lasting effects on environmental health. A cross-sectoral approach to communication and preparedness responses is needed to coordinate surveillance and biosecurity measures to control outbreaks. A One health approach will ensure that environmental conservation obligations are met and that the health of people, livestock and wildlife is protected.

There is an urgent need for governments to invest in local and global initiatives targeting the human-animal-environment interface of disease† One such investment includes funding higher education programs in One Health. These programs will prepare the next generation of Canadians to address major societal challenges – such as pandemic preparedness – with a One Health lens, enabling the formation of teams with expertise that transcends disciplinary boundaries.

Now, more than ever, we need to ensure that both local and global One Health initiatives are developed as a core component of preparing for future pandemics.