Highly pathogenic avian influenza A(H5N1) virus in a common bottlenose dolphin (Tursiops truncatus) in Florida

Abstract

Since late 2021, highly pathogenic avian influenza (HPAI) viruses of the A/goose/Guangdong/1/1996 (H5N1) lineage have continued to cause widespread mortality in wild birds and poultry in the United States. Concomitant with the spread of HPAI viruses in birds are increasing numbers of mammalian infections, including wild and captive mesocarnivores and carnivores with central nervous system involvement. Here we report the first known case of HPAI, A(H5N1) of clade 2.3.4.4b, in a common bottlenose dolphin (Tursiops truncatus) from Florida, United States. Pathological findings included neuronal necrosis and inflammation of the brain and meninges, and quantitative real time RT-PCR revealed the brain carried the highest viral load of tissues tested. Virus isolated from the brain contained a S246N neuraminidase substitution which led to reduced inhibition by the neuraminidase inhibitor oseltamivir. The increased prevalence of A(H5N1) viruses in atypical avian hosts and its cross-species transmission into mammalian species highlights the public health importance of continued disease surveillance and biosecurity protocols.