First report of Photobacterium damselae subspecies damselae in Razorbill (Alca torda)

A razorbill (Alca torda) was found dead in Bacoli, Italy, on January 16, 2023, during an exceptional irruptive event. The bird, a young female weighing 800 g with a moderate nutritional status and no external traumatic injuries underwent a post-mortem examination, which revealed coelomitis with severe congestion of the liver, lungs, kidneys, and myocardium. Lung, liver, kidney, and heart samples were collected for microbiological and histopathological analyses. Bacterial isolation on blood agar showed the growth of spherical/ovoid colonies after 48 hours, consistent with the Photobacterium genus. Identification by MALDI-TOF MS and PCR confirmed the presence of Photobacterium damselae subsp. damselae (Pdd), supported by 16S 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 hemorrhages in the liver, the lung tissue and kidneys. In the myocardium, mild and multifocal lymphocytic infiltrates were present. These findings suggest a significant role of P. damselae subsp. damselae in the observed lesions. The results of the study revealed a new cross-species transmission of this potential zoonotic bacterium and the need for further research in this field. ImportanceWith this study we revealed the first isolation of Photobacterium damselae subsp. damselae in a razorbill but especially the first in a migratory bird. We documented a new cross-species transmission of P. damselae subsp. damselae and the need for further research, highlighting its zoonotic potential and therefore raising concerns about potential implications for marine wildlife, aquaculture and human health. Considering the role of migratory birds in the spread of infectious diseases even over long distances and the effect of climate change on marine ecosystems, and consequently on the circulation of pathogens, it is essential to adopt a preventive approach to mitigate this potential zoonotic risks.