Erysipelothrix rhusiopathiae in stranded harbor porpoises in the Netherlands. Erysipelothrix rhusiopathiae in stranded harbor porpoises in the Netherlands

At the end of August 2021, 190 dead harbor porpoises (Phocoena phocoena) were found stranded on Dutch Wadden Sea islands. Gross pathological assessment revealed an overall moderate to good body condition of the majority of porpoises investigated, but none of the animals recently fed. This suggests a subacute cause of death, with sudden and excessive disease as a likely explanation. No novel, virulent viruses were detected. Phycotoxins were detected in a limited number of individuals. Erysipelothrix rhusiopathiae were isolated from the liver (and other organs) from the majority of investigated porpoises. Based on these findings, E. rhusiopathiae is considered the most likely cause of death of these harbor porpoises. Erysipelothrix infection causes distinctive lesions of which detection would have made the diagnosis complete. Unfortunately, this assessment was hampered by the advanced state of autolysis of carcasses. The very low number of SNPs differing between the isolates suggests common exposure, suggestively through a food source, and/or possibly transmission.