Information on Avian Influenza (Bird Flu) in Scotland
______________________________________________________________________________
HELPLINE INFORMATION
Do not touch or pick up any dead or visibly sick birds that you find. If you find a dead wild mammal, suspected of having been infected with avian influenza, don’t pick it up, note where you saw the dead animal and contact your local area NatureScot Office.
Report dead wild birds to the DEFRA helpline (03459 33 55 77) or online.
If you suspect a case of avian influenza in Scotland, you must report it to your local Field Services Office.
______________________________________________________________________________
A highly infectious strain of avian influenza virus (H5N1) has caused multiple outbreaks in domestic poultry and wild birds across Scotland, in other parts of the UK, and internationally. Symptoms vary between bird species, but the infection can cause severe disease and can cause high mortality rates.
An Avian Influenza Prevention Zone (AIPZ) was declared in October 2022 and is still in place as of February 2023 in Scotland and across Great Britain. England, Wales and Northern Ireland have a mandatory housing order in place, there is no legal housing requirement in Scotland (as of February 2023). All bird keepers are legally required to follow strict biosecurity measures to prevent avian influenza infection in their birds.
Infection has been reported in a range of wild bird species and has caused widespread illness and deaths in wild birds in 2022. Several mammal species that predate or scavenge infected birds, such as foxes, otters, minks, seals, have also been found to be infected. However, the risk to human health is still currently considered to be very low.
BACKGROUND
Avian influenza (bird flu) is a viral disease, and the high pathogenic strains can cause severe disease or death in some poultry and wild bird species. As a Notifiable Animal Disease, it must be reported immediately to authorities.
Avian influenza viruses have been around for a very long time, but the Highly Pathogenic Avian Influenza (HPAI) virus strain (H5N1, clade 2.3.4.4b) that has been circulating in birds across much of the globe since 2021 has been the most long-lasting, widespread and severe on record. The current outbreak is experiencing the highest numbers of cases observed in both domestic and wild bird populations and, unusually, it continued through the summer months with unprecedented mortality of breeding wild birds such as seabirds. Since October 2021, thousands of outbreaks across Europe and other countries across the globe have been detected. The latest figures are available for cases in poultry in Scotland, wild birds in GB and non-avian wildlife in GB. Infections in poultry and mass mortalities of wild birds have now (as of February 2023) been reported in several South American countries, including Argentina, which raises further conservation concerns if the virus reaches Antarctica, which could be devastating to the huge seabird colonies there.
With so many outbreaks occurring in both wild and domesticated birds, the spread of this highly pathogenic strain is of grave concern. Above the usual measures put in place for the prevention, surveillance, and reporting of avian influenza, additional investigations are being conducted in wild and domestic bird populations to identify why this outbreak has been more severe than previous outbreaks.
In addition to domestic and wild birds, several species of mammals have been infected with the currently circulating HPAI H5N1 (2.3.4.4b). These include foxes, otters, mink, seals and sealions, which are predators and scavengers that are thought to have acquired infection from eating infected birds. More unusual mammal species include dolphins, domestic cats, leopards and grizzly bears. Mass infections of American mink through different sheds in a Spanish mink farm provided the first circumstantial evidence that there may now be mammal-mammal transmission. To date (February 2023) around 70 individual mammals in Scotland have tested positive to HPAI, including foxes, otters, grey seals and common (harbour) seals.
HUMAN HEALTH IMPLICATIONS
The risk to human health from the virus is currently very low. Birds are the natural hosts for avian influenza viruses therefore infections in humans are uncommon. However, avian influenza viruses may occasionally infect humans: one human case has been reported in the UK since October 2021. Although evidence of infection was found, there were minimal or no associated illness symptoms in this case, but human infection with H5N1 can cause severe disease.
Those who have close contact with sick birds are at risk of infection with bird flu and should follow public health guidance.
AVIAN INFLUENZA VIRUSES
Influenza viruses are RNA viruses that evolve rapidly, hence the existence of various subtypes and strains. They can affect birds, humans/swine, or other mammals. However, it is rare for strains of avian flu to be transmitted to mammals from birds.
For instance, circulating human seasonal influenza virus strains include two types A’s (H3N2 and H1N1) and type B whereas the circulating strains of avian influenza (bird flu) are predominantly other type A subtypes.
Influenza viruses have two types of surface proteins: Hemagglutinin and Neuraminidase. The current avian influenza H5N1 strain has Hemagglutinin subtype 5 and Neuraminidase subtype 1.
The majority of known subtypes of avian influenza (H1-H16 + N1-N9) are of low pathogenicity to birds. However, a few of these subtypes, specifically those with surface protein Hemagglutinin H5 or H7, can carry a mutation making the strain highly pathogenic to chickens. These so-called ‘high pathogenic’ strains can lead to up to 100% mortality in a chicken's flock within a few days of infection. However, the same strains may be of low clinical impact in other species so facilitating silent spread (e.g. in ducks and geese).
AVIAN INFLUENZA ORIGINS AND SPREAD
A highly pathogenic H5N1 strain emerged in East Asia several years ago, and as descendants from that first lineage (named “Goose/Guangdong 1996”), it has continued to spread and evolve in poultry and wild birds. It caused the 2014/2015 H5N8 outbreaks in Europe, Asia, and North America, the 2016/2017 H5N8 outbreaks in Europe and Asia, and the 2020/21 H5N8/H5N1 outbreaks.
The current 2021/22 season highly pathogenic avian influenza strain detected is known as H5NX (specifically clade 2.3.4.4.b). It is called H5NX because it has been swapping its N (Neuraminidase) for other N-subtypes from circulating low pathogenicity strains over the past few years. Additionally other genomic segments have also been exchanged, with the potential to improve viral adaptation to a wider variety of avian host species. So far, this highly pathogenic virus strain has been detected in birds across Europe, Asia, Africa, North America and South America. The hypothesis is that wild birds migrating in their flyways are contributing to the spread between countries and continents. In fact, the viruses are carried inside the birds’ intestines and are distributed into the environment via bird droppings. There is no evidence that farmed poultry and domestic poultry are driving this current wild bird epidemic within the UK (or Europe).
Some wild bird populations are affected more severely than others, such as barnacle geese (Branta leucopsis) on the Solway Firth in 2021 and the Dalmatian pelicans (Pelecanus crispus) in Greece in early 2022. In Scotland, the main conservation concern is currently for wild great skuas (Stercorarius skua) and northern gannets (Morus bassanus). These seabirds are suffering high mortality at the breeding colonies this year, which is of serious concern because Scotland holds around 60% of the global population of great skuas and around 50% of the global population of northern gannets.
In the wider UK, the strain has caused multiple outbreaks across wild bird species. Migrating wild birds are a probable vector for the spread of avian influenza, with multiple transmission cases to domestic poultry. Thanks to the control measures, to date there has been no farm-to-farm spread in the UK this season
CLINICAL SIGNS: SYMPTOMS AND DIAGNOSIS
Whilst low pathogenic avian influenza (LPAI) is milder, high pathogenicity avian influenza (HPAI) can cause severe disease or be fatal in birds. Clinical signs vary between species of birds but include: sudden death, swollen head, tremors and incoordination, lethargy, blue discoloration of comb and wattles, loss of appetite, respiratory distress, diarrhoea and decrease in egg production.
PREVENTION, SURVEILLANCE AND REPORTING: HOW TO CONTROL AVIAN INFLUENZA
Humans who keep poultry should follow the public health guidance on biosecurity best practices. Those who have 50 or more birds are legally required to register their poultry. All keepers of poultry are encouraged to register their birds so that they receive disease updates rapidly.
To minimise disease spread, keep a close watch on poultry for any signs of disease and seek advice from vets. A sudden and rapid increase in the number of birds found dead may indicate an avian influenza infection. To stop the spread of highly pathogenic avian influenza, infected domestic bird populations are culled. Vaccination of poultry against avian influenza is not currently a routine control measure in the UK.
- An Avian Influenza Prevention Zone (AIPZ) has been in force in Scotland and across Great Britain since 17th October 2022. Bird keepers are required to implement measures to limit the spread of the disease include appropriate cleansing and disinfection of equipment, clothing and housing, movement restrictions and prevention of poultry to wild bird contact (such as protection of food and bedding stores and making sure that housing is secure against birds and vermin).
- Disease control zones including buffer zones around detected cases remain in place across the country as new cases are identified with movement restrictions to minimise disease spread.
Follow the latest updates and find details of current outbreaks and measures in place to prevent the spread of the disease on the government website.
FURTHER INFORMATION
For the latest updates, follow the government’s guidance.
For human health information, please refer to: bird flu and human health.
For more information about biosecurity best practice please refer to: APHA Biosecurity Guidance.