Great Skua Stercorarius skua, killed by bird flu (c) Ashley Cooper rspb-images.com
Todays blog is written by Emma Horton, Senior Policy Officer and our lead on Avian Influenza, she highlights the need to be prepared as avian flu continues to circulate across the globe, with the potential for new outbreaks in the UK at any time.
This is the first of a series of two blogs. Here we update on the current situation with avian flu in the UK and internationally, and the action the RSPB is taking. Our next blog will then outline the essential steps we need Governments to take to reduce the risk of future disease outbreaks and to limit their impacts, alongside the crucial action needed if our already struggling wild bird populations are to recover and be resilient to disease threats.
Background
The avian flu strain responsible for the current global outbreak emerged in 2020, first reaching the UK in summer 2021. It is responsible for the largest and most severe outbreak of the virus on record in the UK and globally.
Low Pathogenic Avian Influenza (LPAI) viruses naturally circulate in wild birds – much like our common colds, typically only causing minor symptoms in infected individuals. However, some sub-types can convert to Highly Pathogenic forms (HPAI). Most conversions have been reported to occur in poultry production systems (37 out of 39). The current outbreak is part of a series beginning in poultry in East Asia in 2003. Following the emergence of a specific viral lineage in domestic geese in Guangdong, China in 1996, which appears to be highly transmissible, there have been increasing detections of HPAI viruses, often associated with mortality in wild birds.
Previous outbreaks of HPAI in the UK have only killed tens of wild birds and tended to be seasonal, impacting waterfowl during the winter. The current strain has had impacts year-round across a wide range of species and has had devastating conservation impacts for species that have never previously been impacted.
In the UK, 78 wild bird species have tested positive since the outbreak began. The majority of these have been seabirds, waterfowl, and birds of prey. Over 350 species have been affected globally. Tens of thousands of birds have died in the UK and millions worldwide.
The current situation in the UK
After the catastrophic impact avian flu has had on our UK seabirds over the last few years, our reserve teams were prepared for the worst this breeding season.
However, since April thankfully there has been just three confirmed cases of avian flu in the UK. A Great Black-backed Gull chick and a Great Skua chick on the Shetland Islands in July, and a Great Skua on the Western Isles in August.
Whilst we hope the low number of cases continues, we are keeping a close eye on the situation and ensuring we are prepared should the worst happen again. Our reserve teams have been working hard monitoring the colonies, and reporting dead birds found to Defra for testing.
Herring Gull Larus argentatus, adult incubating eggs on nest on harbour wall, Tobermory, Isle of Mull, Scotland (c) Ben Andrews rspb-images.com
The current global situation
Elsewhere in Europe cases fell from a peak in February. However, concerningly there have been recent cases in northern France in Herring Gulls and Gannets, in Herring Gulls in neighbouring Belgium and in gulls in north-west Spain and in west and south Portugal. There have also been cases in north Germany in geese, swans, gulls and members of the Phalacrocoracidae family (cormorants/shags), and in Mute Swans in Poland and in Denmark.
Outside of Europe notably, the United States (US) is experiencing an outbreak. Here, the virus has reassorted with a local strain and is now affecting cows (>190 herds across 13 states since March), poultry, domestic cats, wild mammals and wild birds. There have also been a small number of mild cases in people. The virus reached the Antarctic region in October 2023 and is expected to continue to spread in the region. There is a risk it could reach Oceania, currently the only continent unaffected. Since May, Australia has been experiencing outbreaks in poultry. Outbreaks in Australia have not been caused by the H5 sub-type affecting the rest of the world and are a separate disease event.
Cases in Europe present a potential pathway for the virus into the UK. Likewise, recent cases elsewhere on the globe could reach Europe during the Autumn migration. Surveillance and preparedness for outbreaks is essential. Whilst no direct migration routes exist from the US or Australia to the UK, these strains could also reach us in the future.
Why have UK cases been lower this season?
Possible reasons could include flock immunity in some species developed through previous exposure, decreases in the amount of the virus present in the environment, lack of new HPAI virus introductions, and changes in the composition of viral genotypes. At seabird colonies, due to inaccessibility and the risk of disturbance when collecting carcasses, testing is not always possible which can reduce detection of possible cases.
Waves of disease are also typical for influenza viruses, and before 2021 this was the pattern for avian flu in Europe, with winter outbreaks but no cases reported over the summer. In summer, higher temperatures and UV light increase the breakdown of virus in the environment, reducing its spread. Like seasonal flu in humans, these highly contagious viruses can infect a high proportion of the population, but recovered individuals develop an immune response which can prevent re-infection. Usually, this means that once most of the population has been infected, the virus struggles to find new hosts to infect, so cases decline.
However, avian flu can infect a wide range of species and quickly move into new areas through wild bird movements, allowing it to jump into new populations without immunity. For example, in 2023, a change in the virus made it better adapted to gulls, allowing it to infect new populations, particularly of Black-headed Gulls leading to mass-mortality across breeding colonies of this species.
The hope is that enough of our vulnerable wild bird populations have already been exposed to the virus and developed immunity, so flock immunity will protect against large-scale outbreaks. However, over time, immunity wanes, and the virus can change so the immune response is less effective, leading to re-infections. Also, while chicks of previously infected adults may have temporary maternal immunity, it only lasts a short time, after which they are likely to be highly susceptible to disease. This increases the risk of another widespread outbreak.
That's why surveillance is crucial. It helps us to track where the virus is, to understand how it might be changing, and to predict when and where future outbreaks might occur. More research is also needed to understand why we have seen less cases, including the testing of live birds to learn more about immunity which is something we’re investigating in Gannets.
Close up of Gannet, Morus bassanus, eye which is black indicating this individual as a survivor of Bird Flu, photo taken as part of our, GPS tagging, RSPB Bempton Cliffs (c) Sam Turley (rspb-images.com)
Crucial action the RSPB is taking
Current outbreaks elsewhere demonstrate the ability of avian flu viruses to change and how quickly a situation can develop. When the virus hit the UK in 2021, the UK was unprepared. That is a situation our wild birds cannot afford for us to be in again.
Thanks to the generosity of support that we received through our original Avian Flu Appeal and that we continue to receive through our current Wildlife Disease Fund we now have dedicated staff working to optimise the outcome for wild birds in the face of diseases such as avian flu.
We're also joining a new collaborative project led by the Animal and Plant Health Agency to improve surveillance for avian flu in wild birds and mammals, called iPREPARE. On key reserves, we'll be sending samples from dead wildlife and the environment to test for avian flu viruses, to help understand how these viruses circulate in wild populations.
How can you help?
We can’t do this alone, and there are several different ways you can help.
1. Reporting dead birds
If you sadly find dead birds, please do not touch and keep pets away. Instead, follow this guidance on reporting:
If you suspect a wildlife crime, please also report this to your local Police. Further guidance can be found here.
If the dead bird(s) are on an RSPB reserve, please also inform RSPB staff.
2. Wildlife Disease Fund
Diseases are likely to be an ongoing threat to wildlife. It’s important we continue to be able to fund essential scientific research, advocacy and conservation action to tackle disease threats to wild birds. If you would like to help financially support this work, information on how to do so can be found here.
3. Other wild bird disease studies you can support