The worrying discovery in Florida, where the first case of avian influenza virus infection in a dolphin was marked: analyzes detected the presence of the virus in the brain and lungs of the mammal.
The H5N1 avian flu, lethal for millions of birds, continues to cause concern due to the increase in infections also reported in mammalsparticularly in the United States, where researchers at the University of Florida discovered the first case in a dolphin. After the alarm was raised due to the recent spread of the pathogen among dairy cows in Texas and Kansasthe avian influenza virus has been found in brain and other tissue samples of the cetacean during an examination post-mortem.
The dolphin, still alive, had been spotted between a seawall and a port pylon in Horseshoe Beach, a city in southern Dixie County, Florida, but despite initial efforts to remove it from the dangerous situation, the dolphin he died shortly before the operators arrived of the Marine Animal Rescue Program. The case report, detailed in an article just published on magazine Communications Biologyadds dolphins among the mammal species threatened by the virus, which has already caused the death of millions of wild birdsthe killing of half a billion farmed birds and recorded, more and more frequently, lethal infections in mammalsboth terrestrial and marine.
Dolphin killed by bird flu in Florida
The worrying discovery of first case of avian influenza in a dolphin (tursiops truncata) in North America was reported by the Zoological Medicine Laboratory of the University of Florida and confirmed by the National Veterinary Services Laboratory in Ames, Iowa, which characterized the subtype and pathotype of the virus.
Because European authorities are worried about the species jump of avian influenza
Analysis of tissue samples from the cetacean indicated that the specimen had an infection with H5N1 viruses of clade 2.3.4.4bthe same subtype of highly pathogenic avian influenza (HPAI) virus that has been circulating in North America since 2021, where it has affected numerous bird species and mammals in the United States. The virus, the scholars explained, was detected both in the lungs and in the brain tissues of the dolphin, with the brain it presented the highest viral load. Also at the brain level, neuronal necrosis and inflammation of the brain and meninges have been found.
Sequencing of the virus also indicated the presence of mutations associated with the adaptation of the pathogen to mammals and reduced sensitivity to oseltamivir, an antiviral drug used to treat and prevent influenza A and influenza B in humans. “Susceptibility of the virus isolated in dolphins to oseltamivir – the authors of the report specified – was found to be 18 times lower than that of the corresponding avian influenza viruses”.
This means that the virus found in the dolphin tissue samples had mutated until it becomes 18 times more resistant to current pharmacological treatments for influenza, underlining the importance of monitoring these strains and the risk deriving from their spread. What, however, is not yet known is how the dolphin contracted the infection, as the first comparative tests with the viruses detected in seabirds killed by the infection, between Horseshoe Beach and the mouth of the Suwannee River (where it was found the dolphin), seem to exclude that those bird pathogens were direct precursors.
“We do not know yet how the dolphin got the virus and further research is needed – said the article’s corresponding author, Dr. Richard Webby of the World Health Organization (WHO) Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds. More research is also needed to determine how the virus spread to the central nervous system in this dolphin”.