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Avian influenza: how bird flu affects domestic and wild flocks, and why the one health approach is important

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This article was originally published on The Conversation, an independent, non-profit source for news, analysis, and commentary from academic experts. Disclosure information is available on the original website.


Author: Cheyenne Sheriff, Professor of Immunology and Associate Dean, Research and Graduate Studies, University of Guelph and Jeffrey J. Wechtel, Dean, Ontario Veterinary College, University of Guelph

A strain of avian influenza virus is circulating in domestic poultry flocks in Canada, but it does not pose a risk to humans at this point in time.

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Avian influenza, commonly known as avian influenza, is a contagious type A influenza virus that can infect and kill poultry (eg chicken, turkey, pheasant, quail, domestic duck, 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 strains of avian influenza come from: They identify specific HA and NA proteins, such as the current H5N1 strain that is causing outbreaks in Europe, the United States and Canada.

Avian influenza virus types are also classified as highly pathogenic (HPAI) or low pathogenic (LPAI). Highly pathogenic avian influenza viruses – including the current strain of H5N1 – are highly contagious, can cause severe disease and high mortality (90-100 percent) in domestic poultry and spread rapidly from flock to flock.

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Avian influenza: where is it?

Pathogenicity (ability to cause disease) is defined in terms of disease severity in domestic poultry. However, the spread of bird flu is not limited to this population. The H5N1 virus is widespread in wild bird populations around the world. Large outbreaks have been detected in Asia, Africa and Europe since October 2021.

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

Avian influenza and animal health

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Wild birds can be infected with bird flu that is highly contagious and does not show signs of illness. They can transfer disease to new areas when migrating, exposing domestic birds to the virus.

An affected bird may show signs such as coughing, gasping for air, swollen head, and diarrhea. Because influenza viruses in birds can replicate in tissues outside the respiratory tract, infected birds may also display neurological signs including paralysis and tremors.

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

The fallout from the outbreak is being experienced and felt by farmers throughout the agricultural sector. When outbreaks occur, it is often the policy to cull all poultry, whether infected or healthy, to help contain the spread of the virus. This represents huge economic losses for farmers, which can have a long-term impact on their livelihoods and well-being.

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Of course, the bird flu virus does not differentiate between farm and field; It may wipe out wild birds as well as cultivated flocks, and mass mortalities were reported in the UK and Israel in 2021 and 2022. In addition to disrupting the local environment, often including carefully calibrated food webs, such outbreaks occur at the expense of Biodiversity.

Avian influenza virus and environmental health

It is impossible to ignore the effects of climate change on the disease environment. Migratory birds – especially waterfowl – are a natural reservoir for avian influenza virus. When birds migrate and mix with other individuals and flocks, the viruses “drift” and “transform,” meaning that the viral genetic material may change in unexpected ways.

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In the context of avian influenza and climate change, as migration paths and seasons change, previously separated groups of migratory birds are now confronting each other, raising the potential for new viral variants to emerge.

Avian influenza virus and human health

Several avian influenza subtypes, including the H5 subtype, have been shown to cross species, transmitting from birds to mammals — including dogs, cats, pigs, and humans. It is important to note that these events are rare and that the avian influenza virus does not currently pose a risk to human health.

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

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Given the potential for avian influenza to spread rapidly among animals, a robust surveillance program to monitor the evolution and diversity of avian influenza viruses in order to take preventive action is an essential public health measure.

Avian influenza virus and one health

Management and control of avian influenza virus requires a “one health” approach, which gives equal importance to measures that address avian influenza virus from an animal, human and environmental health perspective.

Climate change, population growth, and socioeconomic factors have long-term impacts on environmental health. A cross-sectoral approach to communication and preparedness responses is needed to coordinate surveillance and biosecurity actions that would control outbreaks. One Health’s approach will help ensure that conservation commitments are met and protect the health of people, livestock and wildlife.

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There is an urgent need for governments to invest in local and global initiatives that focus on the interaction between humans, animals and the environment for disease. One such investment includes funding for One Health’s higher education programs. These programs will prepare the next generation of Canadians to meet major societal challenges — such as pandemic preparedness — from a single health perspective, enabling the formation of teams whose expertise transcends disciplinary boundaries.

Now, more than ever, we need to ensure that local and global One Health initiatives are developed as an essential component of preparedness planning for future pandemics.


Cheyenne Sheriff receives funding from Food from Thought, the Canadian Poultry and Egg Farmers Research Council of Canada, and the Saskatchewan Chicken Industry.

Jeffrey Wechtel is president-elect of the Board of Deans for Agriculture, Food, and Veterinary Medicine


This article has been republished from The Conversation under a Creative Commons license. Disclosure information is available on the original website. Read the original article:



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2022-05-26 15:30:18

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