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.

2021年8月末，共计190头死亡港湾鼠海豚（Phocoena phocoena）被发现搁浅于荷兰瓦登海诸岛屿。大体病理学检查显示，多数受检鼠海豚整体身体状况为中度至良好，但无一头存在近期进食迹象。这提示其致死原因为亚急性病程，突发且病情过重的疾病或为最可能的解释。未检测到新型强毒病毒，仅在少量个体中检出藻毒素。多数受检鼠海豚的肝脏及其他器官中分离出了猪红斑丹毒丝菌（Erysipelothrix rhusiopathiae）。基于上述发现，该菌被认为是这批港湾鼠海豚最可能的致死原因。丹毒丝菌感染会引发特征性病变，若能检出此类病变即可完成确诊。遗憾的是，尸体自溶程度严重，阻碍了该病变检测工作的开展。上述分离株之间的单核苷酸多态性（Single Nucleotide Polymorphisms, SNPs）差异位点极少，提示这批鼠海豚存在共同暴露源——推测为食物来源，亦或存在传播途径。