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Severe bird flu season brings impetus to tackling virus

Damaging, long-term outbreak highlights need for scientific interventions to track and target disease in poultry.

Wild seabirds have long been a feature of Scotland’s islands and coastlines, to which they come ashore to breed. This breeding season, however, has been unlike others that have come before.

Birds such as gannets, cormorants and great skuas are dying from avian flu in colonies across the country, with wildlife charities concerned that the impact of widespread infection could lead to long-term population declines.

These wild birds are victims of the largest outbreak of bird flu to date in the UK and parts of Europe.

They are among many thousands around the world to have perished in recent months, in an outbreak that has swept Asia, Africa, Northern Europe and North America.  

Domestic birds have also been badly affected.

Since October 2021, the H5N1 strain has caused nearly 3,000 cases in poultry in dozens of countries, and more than 77 million birds have been culled to curb the spread of the virus, according to Nature.

Circulating infection

Seasonal strains of bird flu originate in South East Asia, from where migratory birds spread the disease to other regions, enabling infections to reach wild and domestic birds around the world during the winter season, and now, enduring through summer.

For the past four years, circulating strains of avian flu have all been classified as highly pathogenic – a type that is able to cause severe disease.

“This is the biggest outbreak we’ve seen, and we don’t know why it’s happening,” says Professor Paul Digard, Chair of Virology at the Roslin Institute.

Professor Digard is one of a team of experts from around the UK seeking to find out what has changed, in a £1.5 million study of bird flu.

The collaboration aims to understand how current strains are able to form larger, longer outbreaks than in previous seasons, and how the virus is able to penetrate poultry premises.

Researchers will also investigate infection and spread of disease in various bird populations, including how the virus transmits from wild to farmed birds, and why some species, such as ducks, are more resistant than others to bird flu.

The team will map and model the spread of infection over time and across species, and develop models to predict how the viruses will evolve and spread.

The consortium, known as Flu-MAP, is led by the Animal Plant Health Agency (APHA) and funded by the Biotechnology and Biosciences Research Council (BBSRC) and the UK Government’s Department for Environment, Food and Rural Affairs (Defra).

​​​​​​​This is the biggest outbreak we’ve seen, and we don’t know why it’s happening.

Professor Paul DigardChair of Virology, the Roslin Institute

Evolving characteristics

The severity of current strains may be attributable to randomly occurring changes to the surface proteins on the flu virus, so they now match the receptors to which they attach in wild birds, which could change how the disease hits different species, Professor Digard suggests.

Alternatively, the virus may be becoming more stable in the environment, for example being able to survive in pond water over summer instead of breaking down amid warm temperatures and exposure to sunlight, he adds.

“Flu is a definitive One Health problem, affecting the environment, animals and people, and we absolutely have to consider a holistic approach,” he says.

Understanding how and why outbreaks develop and spread depends on surveillance efforts.

This currently involves confirming cases in dead birds, which can be analysed to provide valuable information, but a real-time monitoring tool would be a welcome benefit.

When disease strikes animals on farms that there is often very little we can do … testing is often the best tool in our kits to curb disease spread. By testing for avian influenza in ponds, we get one step ahead of this virus.

William DabriVeterinary student

Veterinary student William Dabri is developing a method of tracking bird flu in the environment by sampling sediment from lochs and ponds visited by bird populations, testing for traces of virus originating in bird faeces.

Mr Dabri’s idea was inspired by an internship with the Canadian Food Inspection Agency and by discussions with a visiting researcher to Roslin, Dr Michelle Coombe of the British Columbia Ministry of Agriculture, Food, and Fisheries, whose team has developed a method of sampling bird flu from wetland sediments.

“By testing the sediment in ponds, we can test the amount of influenza that is excreted in bird faeces and the strains these birds are carrying, in real time,” he said.

“When disease strikes animals on farms that there is often very little we can do … testing is often the best tool in our kits to curb disease spread. By testing for avian influenza in ponds, we get one step ahead of this virus.”

The development comes at a critical time, when infections run in high numbers. It may subside in future, when sufficient numbers of birds have survived infection and herd immunity is reached, or the virus may evolve to lose its predilection to affect seabirds. However, research continues to be vital.

“This disease will become less damaging,” explains Professor Digard. However, he cautions, we cannot afford to disregard its potential to reinvent itself. Avian flu potentially may spill into other species – such as people, sea mammals or wild land mammals. With this in mind, it is important that society, and science, continues to prepare for future outbreaks.

** The Roslin Institute receives strategic investment funding from the Biotechnology and Biological Sciences Research Council and it is part of the University of Edinburgh’s Royal (Dick) School of Veterinary Studies. **

Related links

UK scientists join forces to tackle bird flu

Bird flu tests sought to assess emerging strains

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