A dead bottlenose dolphin in Dixie County, Florida, was found to have contracted highly pathogenic avian influenza, or HPAIV, making it the first cetacean virus found in America and the second known case in the world.
A male baby dolphin was recovered in March at Horseshoe Beach by the University of Florida’s marine animal rescue team. A collaboration between UF College of Veterinary Medicine researchers and state and federal laboratories has identified unexpected infection with HPAIV, commonly known as bird flu. The virus recovered from the dolphin belongs to clade 220.127.116.11b of the H5 Eurasian viral lineage.
Wild birds spread widely in North America and Europe this year. The virus primarily infects wild birds and domesticated poultry but rarely humans. Researchers suspect the dolphin became infected by interacting with a wild bird killed by HPAIV.
She leads the animal rescue team and conducts dolphin autopsies with others, said Mike Walsh, DVM, a clinical associate professor with the UF College of Veterinary Medicine.
There was only one report of H5 clade 18.104.22.168b in people in 2022.
Richard Webby, PhD, directs the WHO Collaborative Center for Studies on Influenza Ecology in Animals and Birds at St. Jude Children’s Research Hospital. Jude, which analyzes animal influenza viruses and their potential risks to human health, will analyze dolphin tissue samples provided by the UF team.
“The virus has some features that make further study and follow-up of mammalian cases important, but the virus does not currently have the features that we know are required for transmission between humans and potential mammalian hosts,” Webby said. “In addition, the recent discovery of HPAIV in porpoise in Sweden almost certainly indicates that the discovery of dolphins in Florida is not a unique event.”
The UF team didn’t immediately suspect anything out of the ordinary when they performed a routine autopsy. Tests for common causes of dolphin deaths turned out to be negative.
“However, this dolphin has inflammation in the brain as well as the tissues surrounding the brain, known as the meninges,” said Robert Osipov, PhD, associate professor of veterinary anatomical pathology at UF. “This discovery was extraordinary.”
Andrew Allison, PhD, assistant professor of veterinary virology at UF, studies viruses that commonly circulate in wildlife populations, particularly birds and wild mammals. He knew HPAIV was a rapidly growing concern for Florida’s wild bird populations.
“Although avian influenza infection has never been documented in dolphins, the high incidence of the virus in wild birds within the state in the spring—specifically waterfowl species such as ducks, gulls, terns and herons—suggests that dolphin encounters and death or That dead birds near the shore were not beyond the realm of possibilities.
Wild birds that succumb to HPAIV often have neurological signs with the virus in their brains. Since the dolphin had inflammation of the brain and meninges that could be caused by a virus, Allison thought the dolphin could have died from an HPV infection.
On the basis of these initial suspicions, UF researchers sent brain and lung samples from the dolphin to the Bronson State Animal Disease Diagnostic Laboratory in Kissimmee, a nationally accredited facility and member of the National Animal Health Laboratories Network, or NAHLN. This laboratory is approved to perform routine testing for high-consequence animal pathogens that can pose serious threats to animals and humans. There, suspicions were confirmed, as the samples tested positive for bird flu. As the NAHLN Laboratory, avian influenza finds are sent to the National Veterinary Diagnostic Laboratory in Ames, Iowa, for genetic sequencing to identify the specific strain of avian influenza.
The UF Marine Animal Rescue Team is a member of the National Oceanic and Atmospheric Administration’s Southeast Regional Wrinkles Network, which mandates members to assist and investigate stranded marine mammals. UF Rescue Team works closely with the stranding network, especially when investigating pathogens with unknown effects in cetaceans.
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