Hunt down bird flu to protect Australia

Over the past two years, as the world grapples with the COVID-19 pandemic, another deadly disease has gained momentum in birds – avian flu.

The scale of the current avian influenza outbreaks is unprecedented and accelerating.

Since the beginning of October 2021, there have been more than 4,000 separate outbreaks of avian influenza virus reported in Africa, North America, Asia and Europe. It is more than three times the annual average between 2005 and 2019.

Digitally colorized transmission electron microscope image of avian influenza A H5N1 virus particles (in gold). Photo: Centers for Disease Control and Prevention/Public Health Image Library

Some wild bird populations have been hit with mass deaths, while millions of poultry have been culled in a bid to control disease outbreaks and protect chicken stocks.

For example, 37.55 million poultry have been slaughtered in the United States since January of this year. Cullings of this magnitude have serious socio-economic repercussions, not only for the poultry sector itself, but also on rising poultry and egg prices in many countries.

The increasing number of epidemics is also a concern for humans.

There have been more than 2000 human cases of bird flu since 2005although the vast majority of these are due to the H7N9 virus subtyperather than the H5 subtypes characterizing current outbreaks. The continued spread of H5 subtypes, and the re-emergence of H5N1 in particular, is of concern due to the possibility of the virus jumping from birds to humans.

Between 2003 and 2021, there have been 863 human cases of H5N1 subtype, resulting in 456 deaths – although there have been very few since 2008.

However, the infection rate in humans is very low considering the billions of poultry and hundreds of thousands of workers and farmers involved. There has also been no human-to-human transmission.

But the situation needs to be closely monitored.

In China last year, there were 33 cases of H5N6 strain with 11 deaths reported, and oneBy March this year, there had been 17 cases in China and at least five deaths. Again, there was no human-to-human transmission.

Currently, only countries like China and Vietnam routinely vaccinate poultry against H5 avian influenza. However, the scale of the outbreaks, coinciding with the return of the H5N1 subtype combination, means authorities should consider mass vaccination of poultry.

Outbreaks of highly pathogenic avian influenza pose a serious threat to poultry stocks. Photo: Getty Images

For example, in 2017, mass vaccination was used against H7N9 strain and succeeded in reducing viral loads in chickens, significantly reducing human infections to zero.

The current outbreak highlights the need for continued surveillance in Australia given the risk of transmission from migratory wild birds to domestic poultry. Current epidemics are wreaking havoc on some wild bird populations.

For example, up to 10,000 common cranes (Grus Grus) were found dead in Israel in Decemberwhile since November 8,000 to 10,000 barnacle geese (Branta leucopsis) are said to have died in the UK.

Recently, hundreds of Dalmatian pelicans (Pelecanus crispusin) were found dead in northern Greece.

Since 1976, there have been eight outbreaks of highly pathogenic avian influenza in Australian poultry. A highly pathogenic avian influenza is the most lethal to poultry – most strains of avian influenza are mildly pathogenic in the sense that they cause few signs of disease.

Australia’s most recent outbreak of highly pathogenic avian influenza occurred in 2020 in Victoria, and resulted in the culling of approximately 500,000 poultry.

To date, all previous outbreaks of highly pathogenic avian influenza in Australia have been the result of local/domestic strains that developed in Australia, rather than foreign strain introductions.

Classification of avian influenza viruses. Graphic: provided

To date, all previous highly pathogenic avian influenza outbreaks in Australia have been the result of local/domestic strains that evolved in Australia, rather than foreign strain introductions..

It is important to note that the highly pathogenic viruses that have caused outbreaks in Australia before, which were all H7 viruses, are different from the highly pathogenic H5 avian influenza viruses that are wreaking havoc overseas.

Thus, despite the intensity of the ongoing epidemics abroad, the risk of incursion and subsequent outbreaks due to highly pathogenic H5 in Australia remains low.

Australia monitors bird flu across the National Wild Bird Avian Influenza Program which, since 2005, has collected more than 100,000 samples from wild birds.

In a recent study we published in the journal PLoS Pathogenswe have analyzed over 300 genomes of these low pathogenic avian influenza viruses in wild birds to understand how these viruses move between Australia and the rest of the world.

Overall, what we have found is that bird flu viruses move from wild birds in Asia to Australia, circulate here and die out here. In other words, in the dataset, there was only one case of the virus moving from Australia to Asia.

Based on the scheme of the introductions, we believe this process is facilitated by shore birds (also called waders), which are incredible avian athletes, migrating from Siberia to Australia and back every year.

Avian influenza is brought to Australia by shorebirds (or wading birds) migrating from the northern hemisphere. Photo: Getty Images

While ducks are important for the spread of bird flu in Australia, they are unlikely to be responsible for introducing the virus to Australia – as there are no duck species that migrate between Asia and the region. Australian-Papuan.

However, in our analysis, we found that the way viruses moved around Australia was consistent with the movement of ducks as they use interstate watersheds and disperse widely across the continent in search of water.

But although the risk of a highly pathogenic bird flu virus reaching Australia directly is low, it is important that we continuously monitor the situation.

Our study marks the first time a genomic study of this magnitude has been undertaken in Australia, and the first time ever that all state and territory laboratories have cooperated to provide genome data for avian influenza.

Cooperation between states and territories is so important that it allows us to have a global picture of the variants of avian influenza circulating in the country and how they are introduced.

As I have explained, outbreaks of avian influenza, particularly outbreaks of highly pathogenic avian influenza, affect poultry, wild birds and have consequences for humans.

Continued collaboration between laboratories will be essential to allow us to establish a clear picture and to protect ourselves against any future devastating epidemics.

Banner: A UK government notice warning of an outbreak of bird flu on January 25, 2022 in Windsor. Mark Kerrison/In pictures/Getty Images

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