Detection of Zoonotic Photobacterium damselae Subspecies damselae in a Razorbill (Alca torda): The First Report of a Potential Cross-Species Transmission in Birds

: A razorbill (Alca torda) was found dead in Bacoli, Italy, on January 16, 2023, during an exceptional irruptive event. Post-mortem examination revealed coelomitis with severe congestion of the liver, lungs, kidneys, and myocardium. Bacterial isolation, MALDI-TOF MS analysis and PCR confirmed the presence of Photobacterium damselae subsp. damselae (Pdd), supported by 16S rDNA gene sequencing and detection of the ureC gene. PCR screening for virulence factors identified the hlyAch gene in lung samples, suggesting a potentially pathogenic strain in avian species. Histopathological examination showed severe inflammatory infiltrates and widespread haemorrhages with mild and multifocal lymphocytic infiltrates in tissues analysed. These findings suggest a significant role of Pdd in the observed lesions. Pdd is an emerging pathogen affecting a wide range of marine animals, including invertebrates, fish, and cetaceans. Here, we report the first isolation of Pdd in a razorbill and more importantly, the first detection in a migratory bird. We report a potential new cross-species transmission of Pdd, underscoring its zoonotic potential and the need for further research. Given the role of migratory birds in pathogen spread and the impact of climate change on marine ecosystems, a preventive approach is essential to mitigate risks to wildlife, aquaculture, and human health.