Unfortunately, bird flu shows no signs of slowing down. As well as infecting scores of bird life and even showing up in milk, the virus has been known to spread to mammalian species, including bears, and seals. Now, new research reports the first case of highly pathogenic avian influenza (HPAI) virus in a common bottlenose dolphin (Tursiops truncatus) observed in Florida. 

The clade of 2.3.4.4b A(H5N1) viruses has been seen in common dolphins (Delphinus delphis), harbor porpoises (Phocoena phocoena), and an Atlantic white-sided dolphin (Lagenorhynchus acutus) in places such as Peru, the United Kingdom, Sweden, and Canada, highlighting how widespread this virus can be found in cetaceans. 

Some of the mammal species are suspected to have caught the virus through consuming infected birds. Examination of these carcasses and other species with the disease have shown meningoencephalitis, a condition involving swelling and inflammation of the area around the brain and spinal cord. This can cause unusual behaviors in the species that exhibit these symptoms prior to passing away. 

On March 29, 2022, a dolphin was reported to be in distress and trapped between a seawall and a dock piling near West Horseshoe Beach in Dixie County, Florida. The team arrived to find the dolphin had died despite attempts to free the dolphin from the channel. 

“We still don’t know where the dolphin got the virus and more research needs to be done,” said Dr Richard Webby, who directs the World Health Organization Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds at St. Jude’s, in a statement,

A postmortem revealed that the male dolphin was in a thin body condition, with an empty gastrointestinal tract and numerous lacerations to the body. On closer examination, the team discovered inflammation in the brain, in a similar manner to those previously seen in other mammal species. 

The presence of A(H5N1) was subsequently tested for and found in the brain tissue samples of the dolphin. Interestingly there was a low detection of HPAI in the lungs of the dolphin and the highest viral load was found in the brain tissues. This is similar to the harbor porpoise from Sweden, which also had meningoencephalitis. 

While this is worrying news, the presence of the virus in this species means officials and researchers can be better prepared for more cases. 

“Now, everybody’s going to be on guard for this,” Dr Michael Walsh, a veterinarian at the University of Florida College of Veterinary Medicine and study co-author, told the New York Times. “And that’ll help tell us how serious this really is for cetaceans on the coastlines.”

The paper is published in the journal Communications Biology.