A first: the avian flu detected in the American dolphin

A bottlenose dolphin found dead in Florida’s Dixie County has been infected with the highly pathogenic avian influenza virus, or HPAIV, making it the first cetacean to be found with the virus in America and only the second known case in the world.

The young male dolphin was recovered in March in Horseshoe Beach by the University of Florida Marine Animal Rescue Team. A collaboration between UF College of Veterinary Medicine researchers and state and federal laboratories has identified the unexpected HPAIV infection, commonly known as bird flu. The virus recovered from the dolphin belonged to the 2.3.4.4b clade of the Eurasian H5 virus lineage.

Wild birds have widely spread H5 clade 2.3.4.4b HPAIV in North America and Europe this year. The virus primarily affects wild birds and domestic poultry, but only rarely infects people. Researchers suspect the dolphin was likely infected from interacting with a wild bird killed by HPAIV.

“While obviously the presence of HPAIV is a concern, the key takeaway for us is that additional caution should be taken by those handling or encountering wild dolphins during rescue events or while performing necropsies,” said Mike. Walsh, DVM, clinical associate professor with UF’s College of Veterinary Medicine who leads the animal rescue team and performed the dolphin autopsy with others.

There was only one report of H5 clade 2.3.4.4b in people in 2022.

Richard Webby, Ph.D., directs the World Health Organization Collaborating Center for Animal and Bird Flu Ecology Studies at St. Jude Children’s Research Hospital. The WHO Center in St. Jude, which analyzes animal influenza viruses and their potential risk to human health, will analyze dolphin tissue samples provided by the UF team.

“The virus has some characteristics that make further study and follow-up on mammalian cases important, but the virus does not currently contain the characteristics we know are necessary for transmission between humans and possibly other mammalian hosts,” Webby said. . “Furthermore, the recent discovery of HPAIV in a porpoise in Sweden almost certainly suggests that the dolphin find in Florida is not a unique and unrepeatable event.”

The UF team did not immediately suspect anything abnormal when they performed a routine autopsy. Tests for common causes of death in dolphins came back negative.

“However, this dolphin had inflammation of the brain and also of the tissues surrounding the brain, known as the meninges,” said Robert Ossiboff, DVM, Ph.D., associate professor of veterinary anatomical pathology at the UF. “This discovery was unusual.”

Andrew Allison, Ph.D., assistant professor of veterinary virology at UF, studies viruses that normally circulate in wildlife populations, primarily wild birds and mammals. He knew that HPAIV was a rapidly growing concern for wild bird populations in Florida.

“Although bird flu infection has never been documented in a dolphin, the high incidence of the virus in wild birds within the state in spring – especially waterfowl species such as ducks, gulls, terns and herons – has suggested that encounters between dolphins and dying or dead birds near the coast were not out of the realm of possibility, “he said.

Wild birds that succumb to HPAIV often have neurological signs with viruses found in the brain. Because the dolphin had inflammation of the brain and meninges that may have been caused by a virus, Allison believed the dolphin may have died from HPAIV infection.

Based on these initial suspicions, UF researchers sent samples of the dolphin’s brain and lungs to the state’s Bronson Animal Disease Diagnostic Laboratory in Kissimmee, a nationally accredited facility and a member of the National Animal Health Laboratory, or NAHLN network. . This laboratory is approved and regularly tests for animal pathogens with significant consequences that can pose serious threats to animals and humans. There, the suspicions were confirmed, as the samples tested positive for avian flu. As a NAHLN laboratory, avian influenza findings are sent to the National Veterinary Diagnostic Laboratory in Ames, Iowa, for characterization by genetic sequencing to identify the specific avian influenza strain.

UF’s Marine Animal Rescue Team is a member of the National Oceanic and Atmospheric Administration Southeast Regional Stranding Network, which authorizes members to witness and investigate beached marine mammals. The UF rescue team works closely with the stranding network, especially when investigating pathogens with unknown effects in cetaceans.

Media Contact: Sarah Carey, [email protected], 352-294-4242

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