(Portland) Avian flu is killing tens of thousands of seals and sea lions around the world, disrupting ecosystems and baffling scientists who see no clear way to slow the devastating virus.
The global avian flu epidemic that began in 2020 led to the deaths of millions of domestic birds and spread to wildlife around the world. This virus is not considered a major threat to humans, but its spread into farms and wild ecosystems has caused widespread economic upheaval and environmental disruption.
Seals and sea lions, in places as far apart as Maine and Chile, appear to be particularly vulnerable to the disease, scientists say. The virus has been detected in seals on the east and west coasts of the United States, leading to the deaths of more than 300 seals in New England and a handful more in Puget Sound, Washington. The situation is even more serious in South America, where more than 20,000 sea lions have died in Chile and Peru and thousands of elephant seals in Argentina.
The virus can be controlled in domestic animals, but it can spread unchecked in wildlife. Marine mammals, such as South American seals, that were not exposed to the virus suffered devastating consequences, said Marcela Uhart, Latin America program director at the Karen C. Drayer Wildlife Health Center from the University of California, Davis.
“Once the virus is present in wildlife, it spreads like wildfire, as long as there are susceptible animals and species,” Ms.me Uhart. Animal movements spread the virus to new areas. »
Scientists are still figuring out how the seals contracted bird flu, but it’s likely they came into contact with infected seabirds, Dr.me Uhart. Since the arrival of the virus at the end of 2022, marine mammals in South America have regularly suffered high mortality, and birds in Peru and Chile have died by the hundreds of thousands as a result of the virus. since then.
The virus continues to spread and was first detected in mainland Antarctica in February.
The deaths of seals and sea lions disrupt ecosystems in which marine mammals serve as key predators at the top of the food chain. Seals contribute to the balance of the oceans by preventing overpopulation of the fish species on which they feed.
Many affected species, such as South American sea lions and southern elephant seals, have relatively stable populations, but scientists worry that the virus could spread to more endangered animals. Scientists have estimated that bird flu may have played a role in the deaths of hundreds of endangered Caspian seals in Russia last year.
“Wildlife loss on the current scale poses an unprecedented risk of collapsing wildlife populations, creating an ecological crisis,” the World Organization for Animal Health, an intergovernmental organization, warned in a statement. communicated.
In New England, scientists at the Cummings School of Veterinary Medicine at Tufts University discovered that an outbreak of avian flu that killed more than 330 gray and harbor seals along the North Atlantic coast in 2022 turned out to be more serious than initially thought. It is possible that the seals contracted the virus by coming into contact with the feces of sick gulls or by attacking an infected bird, the scientists said.
“Marine mammals are still quite unique in terms of the scale of outbreaks that occur,” said Wendy Puryear, one of the study’s authors from Tufts University. One connection is that many viruses circulate among coastal birds. These wild birds have many opportunities to harbor the virus and transmit it to marine mammals. »
Some scientists and environmental advocates believe there may be a link between epidemics, climate change and ocean warming. Warming sea temperatures off northern Chile are reducing the population of forage fish, weakening sea lions and making them more vulnerable to disease, according to Liesbeth van der Meer, director of the environmental group Oceana in Chile.
Scientists and environmentalists hope that vaccinating poultry will help reduce the spread of the disease, Liesbeth van der Meer said, adding that it is also important for people to avoid potentially infected animals in the wild.
“Authorities have carried out campaigns on the disease, strongly recommending not to approach seabirds or marine mammals showing symptoms or found dead in coastal areas,” Ms.me van der Meer.
Even aquarium seals are not considered completely safe from bird flu. The New England Aquarium, where outdoor harbor seal exhibits attract thousands of visitors each year, has taken strict health measures to prevent transmission of the virus to its animals, revealed Melissa Joblon, the aquarium’s director of animal health. from Boston.
Staff are not allowed to bring backyard poultry products into the aquarium, and a canopy protects the seal exhibit from birds that could carry the virus.
“We know this is a risk for the animals that live here,” said Mme Joblon, adding that none of the seals in the aquarium have been infected.
The death of marine mammals is even more worrying due to mutations in the avian virus, according to an article in the journal Nature Communications last fall. These mutations “warrant further examination and highlight the urgent need for active local surveillance to manage outbreaks and limit spread to other species, including humans,” the study said.
Another study, published in the journal Emerging Infectious Diseases in February, found that the avian flu virus has adapted to spread between birds and mammals. Researchers found nearly identical samples of the virus in dead sea lions, a dead seal and a dead seabird. According to them, this discovery is important because it confirms the existence of an epidemic affecting several species of marine mammals and birds.
According to Lynda Doughty, executive director of Marine Mammals of Maine, a marine mammal rescue organization that responded to seals with bird flu during the New England outbreak, more seals died could disrupt essential ecosystems around the world.
“You need a happy ecosystem. If we eliminate some important species, what will be the trickle-down effect? That’s the million dollar question,” asked Mme Doughty.