Over the past two years, we have witnessed outbreaks of highly pathogenic avian influenza causing unprecedented impacts on wildlife. The disease affects millions of poultry in Europe, Asia, Africa and North America, causing alarming mortality among seabirds.
The appearance of dead or dying birds
The current outbreak of highly pathogenic avian influenza (HPAI) is caused by the H5N1 virus, a type A influenza virus first discovered in domestic waterfowl in southern China in 1996. Its ability to mutate and assimilate the genetic material of other viruses has led to the emergence of new variants. The current H5N1 strain of clade 2.3.4.4b is derived from a previously circulating variant and was detected in seabirds in 2020, exhibiting high lethality and infectivity in wild birds.
The 2021-2022 seabird outbreak resulted in the deaths of thousands of different seabirds. In Scotland, 11% of the British great skua population (7% of the world’s population) have died from the virus. Only 22% of individuals of the species returned to Hermanes, the UK’s largest colony, in 2023 from the last census.
The world’s largest Atlantic gannet breeding colony on Bathrock Island (Scotland) also suffered devastating deaths from the disease in 2022. Adult gannet survival rates were 42% lower than the average for the previous 10 years.
Gannets at Bath Rock, Scotland. Kristen Snipe/Unsplash
It is estimated that about 13,200 white-faced barnacles from Svalbard and overwintering in Solway, Scotland, died from highly pathogenic avian influenza between 2021 and 2022, accounting for 32% of the flyway population.
disease remains
After devastating impacts in 2022, scientists and conservationists await the 2023 breeding season with some concerns: How are the populations doing? Will last year’s mass deaths be repeated?
New reports indicate that the virus continues to impact breeding populations of seabirds. In Scotland alone, 9,610 seabirds died between April and October 2023, nearly three-quarters of which were common guillemots (3,519) and kittiwakes (3,367), followed by black-headed gulls (834 ), razorbills, terns, and other seagulls.
Between June and September 2023, 21 European countries reported cases of highly pathogenic avian influenza in different species of poultry (25 birds) and wild birds (482 birds). In Spain, more than 100 cases in wild birds have been reported since 2022, with those detected in sensitive populations of black-legged and black-billed terns in Valencia’s Albufeira Natural Park being particularly worrying.
Researchers track virus
During the 2023 breeding season, our research group at the University of Edinburgh, together with staff from the British Center for Ecology and Hydrology, conducted a systematic sampling of several species of seabirds on the Isle of May (Scotland).
Adult individuals of puffins, razorbills, guillemots, kittiwakes and cormorants were sampled to assess the incidence of the virus and to determine whether antibodies indicative of previous infection were present in apparently healthy birds. The results, which are still in the final stages, suggest that while responses to infection may differ between species, large numbers of individuals may still be susceptible to the virus.
A specimen of the kittiwake (Rissa tridactyla) on the Isle of May in Scotland, one of the species most affected by highly pathogenic avian influenza.Francisco Ruiz Laia
Can some birds survive infection? An intriguing study led by the RSPB’s Conservation Science Team has revealed the presence of individuals in a population of Bass Rock gannets with black, mottled irises rather than the usual light blue.
After collecting samples from apparently healthy adult birds, the researchers found that individuals with dark irises displayed antibodies derived from previous infections. This suggests that some people were able to recover after the 2022 outbreak, and that dark irises could be a sign of previous infection.
What’s the future for seabirds?
Seabirds face significant pressure due to climate change, the impact of certain fishing gear, invasive species or coastal urbanization. Highly pathogenic avian influenza poses an additional threat, and although the severity of its impact has not yet been fully assessed, northern Europe has experienced unprecedented population declines.
Research centers and conservation organizations conduct systematic sampling to better understand how each species responds to infection. Authorities then consider interventions to protect key species or, to a greater extent, indirect actions, taking into account the impact of external pressures that may exacerbate the impact of the disease.
Controlling this disease requires a strong commitment from the commercial breeding and game bird communities to increase awareness of the symptoms of the disease and promote biosecurity and animal welfare. These agencies also promote citizen participation by notifying sick or dead birds and always avoiding contact with dead or symptomatic birds.
New highly pathogenic avian influenza outbreaks are likely to occur in the future, so new epidemiological and ecological research is critical to help understand and mitigate the impact of this virus on seabirds. Given growing concerns about the rapid spread of the virus and its adaptation to new hosts, these investigations will provide valuable information for human health.
global issues
Since its emergence in 1996, there have been warnings that the H5N1 virus could become a pandemic. From 2003 to 2023, 878 human cases, presumed to be caused by contact with infected birds, were reported from 23 countries, of which 458 (52%) were fatal. Current human infections with the H5N1 strain of clade 2.3.4.4b are sporadic and, according to experts, the current risk of infection is low.
An increase in cases in marine mammals, or a recent outbreak at a mink farm in Spain, has raised concerns that the virus may be spreading naturally between mammals. Although evidence of this type of transmission remains variable, cases have been confirmed in more than two dozen mammals in Europe and the Americas.
Experts are concerned about the virus’s recent arrival in the Antarctic region and its impact on local fauna, following its rapid spread. Understanding the spread of disease in nature and moving towards sustainable and environmentally friendly poultry farming will be key to protecting wildlife and ensuring a healthy future for all.
Francisco Ruiz-Raya, NERC Postdoctoral Fellow, University of Edinburgh and Emma Cunningham, professor of ecology and disease, University of Edinburgh
This article originally appeared on The Conversation. Read the original article.