he young male 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 identified the unexpected infection with HPAIV, commonly known as bird flu. The virus recovered from the dolphin belonged to clade 2.3.4.4b of the Eurasian H5 viral lineage.

Wild birds have spread H5 clade 2.3.4.4b HPAIV widely in North America and Europe this year. The virus primarily affects wild birds and domesticated poultry but only rarely infects people. Researchers suspect the dolphin likely got infected by 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, D.V.M., a clinical associate professor with UF’s College of Veterinary Medicine who leads the animal rescue team and performed the dolphin’s necropsy with others.

There has been 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 Studies on the Ecology of Influenza in Animals and Birds at St. Jude’s Children’s Research Hospital. The WHO Center at St. Jude, which analyzes animal flu viruses and their potential risk to human health, analyzed the dolphin tissue samples supplied by the UF team.

“The virus has some features that make further study and follow-up on mammalian cases important, but the virus does not currently contain the features we know are required for transmission between humans and likely other mammalian hosts,” Webby said. “In addition, the recent discovery of HPAIV in a porpoise in Sweden almost certainly suggests that the Florida dolphin finding isn’t a one-off, unique event.”

The UF team did not immediately suspect anything out of the ordinary when they performed a routine necropsy. Tests for common causes of deaths in dolphins turned up negative.
“However, this dolphin had inflammation of the brain and also the tissues surrounding the brain, known as the meninges,” said Robert Ossiboff, D.V.M., Ph.D., an associate professor of veterinary anatomical pathology at UF. “This finding was unusual.”

Andrew Allison, Ph.D., an 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 avian flu infection had never been documented in a dolphin, the high incidence of the virus in wild birds within the state in the spring — specifically aquatic bird species such as ducks, gulls, terns and herons — suggested that encounters between dolphins and dying or dead birds near the shoreline was not out of the realm of possibility,” he said.

Wild birds that succumb to HPAIV often have neurologic signs with virus found in their brains. Since the dolphin had inflammation of the brain and meninges that could have been caused by a virus, Allison believed that the dolphin could have died from HPAIV infection.

On the basis of these initial suspicions, the UF researchers sent brain and lung samples of the dolphin to the state’s Bronson Animal Disease Diagnostic Laboratory in Kissimmee, a nationally accredited facility and a member of the National Animal Health Laboratory network, or NAHLN. This lab is approved for and routinely performs testing for animal pathogens of significant consequence that can pose severe threats to animals and humans. There, suspicions were confirmed, as the samples tested positive for avian flu. As a NAHLN laboratory, avian flu detections are sent on to the National Veterinary Diagnostic Laboratory in Ames, Iowa, for characterization by genetic sequencing to identify the specific strain of avian flu.

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

FRONT:
Helena Hauck de Oliveira, D.V.M., is a second-year veterinary anatomic pathology resident at UFCVM with a particular interest in wildlife and zoo animal pathology. She assisted with the dolphin necropsy and with histology performed on the case.

Andrew Allison, Ph.D., an assistant professor of veterinary virology, studies the evolution and emergence of viruses that normally circulate in wildlife populations, specifically wild birds and mammals. After learning the dolphin necropsied at UF had inflammation of the brain and meninges that could have been caused by a virus — and mindful of a high incidence of HPAIV in wild birds in the spring — he suspected the dolphin could have died from HPAIV infection and recommended that tissue samples be sent to the state’s disease diagnostic laboratory for initial confirmation.
Back ( left to right):

Brittany Barbeau, the UF Aquatic Animal Health program’s biological scientist, specializes in marine animal response with an emphasis on marine mammal necropsy, cetacean, manatee and sea turtle rescue and sea turtle rehabilitation. She assisted with the dolphin’s necropsy and managed the samples collected.

Mike Walsh, D.V.M., a clinical associate professor of aquatic animal health and zoological medicine specialist, directs the UF Marine Animal Rescue Program, which responded to reports of a stranded dolphin in Dixie County in late March. Although the dolphin was deceased at the time team members arrived, it was transported back to UF for a gross necropsy, a critical part of disease investigation. Walsh performed the necropsy, during which tissue samples were obtained for routine testing. Those initial tests revealed nothing consistent with known health problems in dolphins. When histology was later performed on tissue samples, however, the findings stood out as unusual.

Rob Ossiboff, D.V.M., Ph.D., a clinical associate professor of veterinary anatomic pathology who also specializes in virology and molecular diagnostics, performed a full microscopic workup of the dolphin, carefully analyzing cells for abnormalities following the animal’s necropsy. He noticed inflammation of the brain and the tissues surrounding the brain, known as the meninges. When tests for typical causes of those findings came up negative, Ossiboff discussed next steps with Walsh and Allison, and samples were then sent to the state diagnostic lab as UF does not have the facilities to perform tests of certain highly pathogenic agents.

Suzanna Mickey, a stranding biologist with UF’s Marine Animal Rescue Program, responded with team staff to the report of a dolphin stranded along a sea wall in Horseshoe Beach in Dixie County. They recovered the dolphin and brought it back to UF, where a necropsy was performed.

Not pictured: Allison Murawski, D.V.M., an intern in aquatic animal medicine, collaborated with multiple organizations, including sending the dolphin’s tissue samples to the state’s diagnostic lab for testing and flying to Memphis, Tennessee, to work with scientists at St. Jude.