Abstract
Between 2015 and the beginning of 2018 (January-March), 30 cetaceans were found stranded along the Ligurian Sea coast of Italy. Necropsies were performed in 22 cases and infectious diseases resulted the most common cause of death. Three striped dolphins, showed a severe coinfection involving the monophasic variant of Salmonella Typhimurium (Salmonella 1,4,[5],12:i:-). The isolates were characterized based on antimicrobial resistance, Multiple-Locus Variable-number tandem-repeat Analysis (MLVA) and whole-genome sequencing (WGS). All isolates demonstrated the same multidrug resistant genotype (ASSuT isolates), showed three different MLVA profiles, two of which closely related, and were identified as Sequence Type 34. Moreover, Single nucleotide polymorphisms (SNP) analysis confirmed strong correlations between two out of the three isolates. To our knowledge, S. 1,4,[5],12:i:-, one of the most common serovars in cases of human infection and food sources worldwide, has not previously been described in marine mammals, and reports of Salmonella-associated disease in free-ranging cetaceans are rare. These results highlight the role of cetaceans as sentinel species for zoonotic and terrestrial pathogens in the marine environment, suggest a potential risk for cetaceans and public health along the North Western Italian coastline and indicate cetaceans as a novel potential reservoir for one of the most widespread Salmonella serovars.
Highlights
The Mediterranean basin represents the largest enclosed sea on earth and an important marine biodiversity hotspot, being surrounded by heavily populated and industrialized coastal areas, which makes the impact of anthropic activities proportionally stronger than in any other basins
Thanks to the surveillance activity of the Italian National Reference Centre for Diagnostic Activities on Stranded Marine Mammals (C.Re.Di.Ma.), necropsies were performed in 22 cases, the cause of stranding was determined with confidence in 19 cases and infectious diseases resulted the most common cause of death (18 out of 19)
Significant gross necropsy findings included a severe state of dehydration, a widespread internal congestion and a mild Phyllobotrium delphini and Monorygma grimaldi infection
Summary
The Mediterranean basin represents the largest enclosed sea on earth and an important marine biodiversity hotspot, being surrounded by heavily populated and industrialized coastal areas, which makes the impact of anthropic activities proportionally stronger than in any other basins. Marine mammals from such regions, show high tissue concentrations of organochlorine (OC) xenobiotics, increasing their susceptibility to other anthropogenic stressors. We report three cases of coinfection, involving striped dolphins found stranded along the coast of the province of Savona (Fig. 2), and characterized by the detection of a monophasic variant of Salmonella 1,4,[5],12:i:in association with cetacean-specific viruses along with pathogens indicative of environmental contamination. Animals that develop septicaemia can die without showing clinical signs or, in some cases, can show complications such as bronchopneumonia, necrotizing hepatitis, splenitis, meningoencephalitis and abscessation
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