The Northern Gannet is found along the coasts of the Atlantic Ocean, breeding in western Europe and northeastern North America. Scotland is home to around half of the world’s breeding population of gannets. A few kilometers off the coast of Scotland, not far from the capital city of Edinburgh, lies the small, rocky island called Bass Rock. More than 150,000 northern gannets nest on the island, making it the largest gannet colony in the world.
In the summer of 2022, gannets on their annual migration to Bass Rock faced a new threat: an outbreak of the highly pathogenic H5N1 avian influenza. This virus, which is often called "bird flu," spreads naturally among wild aquatic birds around the world. It can also infect poultry and other avian and animal species.
Countless dead birds washed up on the coast of Scotland, and seabird experts also saw a lot of dead and dying birds on the colony itself. At the Scottish Seabird Centre, in North Berwick, which looks out over the water towards Bass Rock, chief executive Susan Davies has been witnessing the disaster unfold on the ground. Recalling the events of last summer, she said, "One day in June revealed 5,000 dead birds on that single day... I have worked in nature conservation for thirty years; I have never seen this in these seabird colonies."
The first gannets usually start to return to the island towards the end of February. This year, however, seabird experts are on edge about how many will arrive and if the coming breeding season will bring a repeat of last year.
These dead and dying birds were the first signs that the highly pathogenic avian influenza (HPAI) outbreak would happen in 2022. Avian flu has long been found in wild bird populations, but it was a very mild disease known as low pathogenic avian flu. The new, more lethal type of HPAI known as H5N1 can be traced back to a goose farm in China in 1996. Millions of birds have become infected with the virus since its discovery. It has infected and killed people in the past as well, often through direct contact with infected poultry, such as during slaughter or plucking. Its ability to move from birds to people has been growing since the outbreak, but so far it has not been shown to spread directly from one person to another.
A strain of the virus has evolved over the past year, and become more transmissible, resulting in the biggest outbreak ever seen. In the last few months, the number of mass deaths of wild animals has been growing. This year's strain is especially lethal to seabirds, especially those breeding in colonies where birds congregate in large numbers. This includes Dalmatian pelicans in Greece, knots in the Netherlands, European cranes in Israel, and Caspian terns on Lake Michigan in Wisconsin.
The current outbreak isn't just affecting birds. Near the end of 2022, an outbreak of the virus was discovered at a Spanish mink farm. Genetic sequencing in January revealed that these animals were infected with a new strain which appears to facilitate the spread between mammals. More than 50,000 minks had to be killed at the facility.
In January, hundreds of dead sea lions washed up on the beaches of Peru. Peruvian and Argentine researchers have recently confirmed that the mass deaths were caused by avian flu, which was transmitted when the sea lions fed on the dead, sick birds. In just a few weeks, the avian flu virus killed 585 sea lions. Researchers are not ruling out the hypothesis that the virus may have spread from mammal to mammal. Avian flu has infected mammals many times in the past, but the scale of the current outbreak increases the chance that it could mutate into a variant that is much more dangerous to people.
Culling poultry is a common way of attempting to halt the spread of the virus. There are also ways to reduce the risk of infection. In settings where birds are raised and kept, strict hygiene procedures reduce the danger of disease spread. The places where the birds are kept should be secured from the outside so that wild birds cannot enter, as direct or indirect contact poses a risk of disease transmission between poultry and wild birds. Farmers are now trying unusual tactics to protect poultry, with some using machines that make loud noises to scare off wild birds.
In some parts of the world, vaccinations are also being used, with varying degrees of success. Mexico and the EU are among those vaccinating or considering shots. Other vaccines are used in poultry: a spray vaccination, vaccination through drinking water, or vaccination through the eggshell in the hatchery. In the US, federal scientists are preparing to test avian flu vaccines in poultry for the first time in years as part of a strategy to combat the increasing outbreak. Vaccination is not a simple solution, but it is an important and useful tool.
The avian flu virus normally follows regular yearly patterns, but the current strain is raising concerns because it is extremely effective at spreading and infecting wild birds. This results in what scientists refer to as "increased infection pressure." Increased virus shedding increases the risk of transmission to domesticated birds kept as pets or in poultry farms. Instead of appearing when migratory birds arrive in the fall and disappearing when they leave in the spring, researchers in the northern hemisphere have observed year-round infection this year. As a consequence, many new species of birds are now being infected.
Seabird populations, which are now being affected by avian flu, were already at risk from a lot of other things. Climate change, overfishing of their prey, by-catch in fisheries, and predation by invasive species are estimated to be threatening more than half of all seabird species.
Ruth Cromie, Wildlife Health Councilor of the Convention on the Conservation of Migratory Species of Wild Animals, calls for national and regional response strategies to be put in place before wild bird populations are impacted by further outbreaks.
She suggests not building poultry farms near places where wild birds live. She also says that officials should determine if collecting dead birds is a good idea, which has remained unclear throughout the current outbreak.
“These are not the last crises that are going to happen in our increasingly polluted planet, with all of these different interfaces between wildlife and people,” she says.
Cover Photo: Gannets return to nesting colony on Alderney island in the English Channel. Feb. 20, 2023.
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