Abstract
Recent population growth of the harbour porpoise (Phocoena phocoena), grey seal (Halichoerus grypus) and common seal (Phoca vitulina) in the North Sea has increased potential interaction between these species. Grey seals are known to attack harbour porpoises. Some harbour porpoises survive initially, but succumb eventually, often showing severely infected skin lesions. Bacteria transferred from the grey seal oral cavity may be involved in these infections and eventual death of the animal. In humans, seal bites are known to cause severe infections. In this study, a 16S rRNA-based microbiome sequencing approach is used to identify the oral bacterial diversity in harbour porpoises, grey seals and common seals; detect the potential transfer of bacteria from grey seals to harbour porpoises by biting and provide insights in the bacteria with zoonotic potential present in the seal oral cavity. β-diversity analysis showed that 12.9% (4/31) of the harbour porpoise skin lesion microbiomes resembled seal oral microbiomes, while most of the other skin lesion microbiomes also showed seal-associated bacterial species, including potential pathogens. In conclusion, this study shows that bacterial transmission from grey seals to harbour porpoises by biting is highly likely and that seal oral cavities harbour many bacterial pathogens with zoonotic potential.
Highlights
The Dutch coastal regions of the North Sea are inhabited by harbour porpoises (Phocoena phocoena), grey seals (Halichoerus grypus) and common seals (Phoca vitulina)
The aim of the study is threefold: firstly, to identify the bacterial diversity and inter-species differences in the oral cavities of grey seals, common seals and harbour porpoises; secondly, to assess commonality in the bacterial diversity found in grey seal oral cavities and bite wounds on harbour porpoises to assess the potential transfer of bacteria and thirdly, to provide insights in the bacterial species with zoonotic potential present in the oral cavities of these three marine mammals, using a 16S rRNA-based microbiome sequencing approach
Samples were collected from 21 stranded harbour porpoises (Phocoena phocoena), of which 20 had skin lesions ascribed to seal attacks, nine grey seals (Halichoerus grypus) and eight common seals (Phoca vitulina) from various coastal sites in The Netherlands
Summary
The Dutch coastal regions of the North Sea are inhabited by harbour porpoises (Phocoena phocoena), grey seals (Halichoerus grypus) and common seals (Phoca vitulina). These species form an important part of the marine ecosystem as apex predators. Hundreds of stranded harbour porpoises with severe mutilations have been reported [5] These mutilations have been attributed to grey seals [6,7], a species which is known to predate on common seals and juveniles of its own kind [8,9,10]. Bacterial species transferred from the seal oral cavity may be involved in these infections and eventual death of these animals
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