PORTLAND, Maine (AP) — Bird flu is killing tens of thousands of seals and sea lions in corners of the world, disrupting ecosystems and baffling scientists who see no clear way to slow the devastating virus.
The bird flu epidemic that started worldwide in 2020 led to the death of millions of domestic birds and spread all over the world. This virus is not thought to be a major threat to humans, but its spread in farming operations and wild ecosystems has caused widespread economic turmoil and environmental degradation.
Seals and sea lions in places as far apart as Maine and Chile appear to be particularly vulnerable to the disease, scientists said. The virus has been detected in seals on the east and west coasts of the United States and has killed more than 300 seals in New England and a handful of seals in Washington’s Puget Sound. The situation is even worse in South America, where more than 20,000 sea lions have died in Chile and Peru and thousands of elephant seals have died in Argentina.
Karen C. Davis, Drayer Wildlife Health Center at the University of California.
“When the virus enters wildlife, it spreads like wildfire as long as there are susceptible animals and species,” Uhart said. “The movement of animals spreads the virus to new areas.”
Scientists are still investigating how seals contract bird flu, but it is most likely from contact with infected seabirds, Uhart said. He noted that high mortality rates have consistently affected South American marine mammals since the virus emerged in late 2022, and that hundreds of thousands of birds in Peru and Chile have since died from the virus.
The virus is still spreading and was first detected on the Antarctic mainland in February.
The deaths of seals and sea lions are disrupting ecosystems in which marine mammals serve as important predators near the top of the food chain. Seals help keep the ocean balanced by preventing overpopulation of the fish species they feed on.
The populations of many affected species, such as South American sea lions and Southern elephant seals, are relatively stable, but scientists are concerned about the possibility of the virus spreading to more endangered animals. Scientists said bird flu may have played a role in the deaths of hundreds of endangered Caspian seals in Russia last year.
“Loss of wildlife on the current scale poses an unprecedented risk of wildlife population collapse and creates an ecological crisis,” the World Organization for Animal Health, an intergovernmental organization, said in a statement. said.
In New England, scientists at Tufts University Cummings School of Veterinary Medicine found that a bird flu outbreak that killed more than 330 harbor and gray seals along the North Atlantic coast in 2022 was worse than initially thought. Scientists reported that the seals may have caught the virus from seagulls by coming into contact with sick seagull feces or by hunting an infected bird.
The US government ruled that the seal death was an “unusual mortality event” attributable to bird flu. The National Oceanic and Atmospheric Administration declared the incident over, but concerns about a possible recurrence remain.
“Marine mammals are still pretty unique in terms of the scale of the epidemics that are occurring,” said Wendy Puryear, author of the Tufts study. “One link is that there are a lot of viruses circulating in shorebirds. There are many opportunities for these wild birds to harbor the virus and transmit it to marine mammals.”
Some scientists and environmental advocates say there may be a link between the outbreaks and climate change and warming oceans. Rising sea temperatures off northern Chile are reducing forage fish populations, making sea lions weaker and more susceptible to disease, said Liesbeth van der Meer, director of environmental group Oceana in Chile.
Van der Meer said scientists and environmentalists are hopeful that vaccinating poultry will help reduce the spread of the disease, adding that it is also important for people to avoid potentially infected animals in the wild.
“Authorities have conducted campaigns regarding the disease and strongly recommend avoiding seabirds or marine mammals that have symptoms or are found dead in coastal areas,” Van der Meer said.
Even seals in aquariums are not thought to be completely safe from bird flu. The New England Aquarium, where open-air harbor seals delight thousands of visitors each year, has taken strict hygiene measures to prevent the virus from spreading to the animals, said Melissa Joblon, animal health director of the Boston aquarium.
He said staff are not allowed to bring backyard poultry products into the aquarium, and an awning protects the seal exhibit from birds that could carry the virus.
“We know this is a risk to the animals that live here,” Joblon said, adding that none of the seals in the aquarium were infected.
Even more alarming are the deaths of marine mammals due to mutations in the avian virus, according to a paper published last fall in the journal Nature Communications. The mutations “require 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 February in the journal Emerging Infectious Diseases, found that the bird flu virus has adapted to spread between birds and mammals. Researchers found nearly identical virus samples in dead sea lions, dead seals and dead seabirds. They said the finding was important because it confirmed a multispecies outbreak that could affect marine mammals and birds.
More seal deaths could disrupt critical ecosystems around the world, said 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.
“You need this happy ecosystem. If we are eliminating some important species, what is the trickle-down effect? That’s the million dollar question,” Doughty said.
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