Bird flu was found in Dolphin in Florida and Porpoise in Sweden

A dolphin swims alongside a boat in the Ten Thousand Islands off the coast of Everglades, Florida, Dec. 2019. (Erik Freeland/The New York Times)

A dolphin swims alongside a boat in the Ten Thousand Islands off the coast of Everglades, Florida, Dec. 2019. (Erik Freeland/The New York Times)

A bottlenose dolphin found dead in a Florida canal last spring has tested positive for a highly virulent strain of bird flu, scientists said Wednesday. The announcement came a week after Swedish officials reported finding the same type of bird flu in a stranded porpoise.

This version of the virus, which has spread widely among North American and European birds, has affected an unusually wide range of species. But these findings represent the first two documented cases in cetaceans, a group of marine mammals that includes dolphins, porpoises and whales.

It’s too early to say how often the virus infects cetaceans, but its discovery in two different species on two different continents suggests there have “almost certainly” been other outbreaks, said Richard Webby, an influenza virologist at St. Jude Children’s Research Hospital. in Memphis, Tennessee.

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“Our surveillance activities on a global scale are never sensitive enough to detect the only two events of this kind,” said Webby, who was not involved in the initial detection of the virus but is now working with the Florida team to monitor it. studies.

The virus has become so widespread in birds that it wouldn’t be surprising to see the pathogen show up in other unexpected species, he added. “Unfortunately, I think this is maybe just kind of an indication of what’s to come if this virus doesn’t go away,” he added.

Experts stress that the risk to humans remains low. In the United States, the circulating version of the virus has caused only one documented human infection, in a person known to have had contact with poultry, according to the Centers for Disease Control and Prevention.

However, the spread of the virus to new species poses potential risks to wildlife and provides the virus with new opportunities to mutate and adapt to mammalian hosts.

This strain of bird flu, known as Eurasian H5N1, has spread rapidly among domestic poultry, affecting tens of millions of farmed birds, according to the Department of Agriculture. Compared to previous versions of the virus, this lineage has particularly affected populations of wild birds, eagles, owls, pelicans and more.

This, in turn, has endangered mammals that encounter wild birds. As the outbreaks spread this spring, the virus appeared in foxes, bobcats, chunks and other species. The virus has also been blamed for a spike in seal infestations in Maine, where bird flu has been detected in both gray seals and fur seals.

The Florida dolphin, a young male, was found in March in a canal in Dixie County, where local residents noticed the animal was trapped between pilings of a pier and a sea wall, said Dr. Michael Walsh, a veterinarian at the University of Florida College of Veterinary Medicine who leads the university’s marine animal rescue program.

By the time rescuers arrived, the dolphin had died, he said. The team, which regularly performs necropsies, collected a variety of samples from the dolphin and stored them until they could be analyzed in more detail.

At the time, scientists had no reason to suspect bird flu had entered the dolphins and were in no rush, said Walsh, who collaborated on the research with Dr. Robert Ossiboff, a veterinarian, and Andrew. Allison, a veterinary virologist, both at the University of Florida College of Veterinary Medicine.

When the results came back this summer, they revealed signs of inflammation in the dolphin’s brain and surrounding tissues, Walsh said. Scientists have previously documented brain inflammation in kit foxes infected with the virus, which can cause neurological symptoms in birds and mammals.

Subsequent laboratory tests identified Eurasian H5N1 in the dolphin’s brain and lungs. “The brain tissue showed a really high level of virus,” Walsh said.

Whether the virus contributed to the dolphin’s death remains unknown, as does exactly how the animal became infected. But it’s not hard to imagine a young dolphin investigating a sick bird near shore, Walsh said, adding, “These animals are always curious about their environment and checking things out. So if he came across a sick, dying or dead bird, he might have been very curious about it. He can mouth it.”

The virus is also responsible for the death of a porpoise found stranded in Sweden in June, the Swedish National Veterinary Institute said last week. The pathogen was found in several of the animal’s organs, including the brain, according to the agency.

So far, there is no evidence that cetaceans transmit the virus to each other, Webby said. And Webby’s team, which has isolated and sequenced the virus detected in the Florida dolphin, has found no signs that it has developed mutations associated with adaptation to mammals. “It still looks a lot like a virus you’d pick up from a bird,” he said.

But now that dolphins and porpoises are known to be susceptible, researchers can start looking for the virus more proactively, including any tissue samples they’ve previously collected.

“Now, everybody’s going to be on the lookout for it,” Walsh said. “And that will help us tell how serious this is for cetaceans on the coast.”

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