Surveillance of amyloidosis in stranded and bycaught cetaceans off Hokkaido, Japan

Systemic amyloidosis is rarely reported among cetaceans, and a surveillance dedicated for its occurrence across a certain geographic location has not been reported. Between 2013 and 2018, comprehensive gross and histopathologic examinations were conducted on 54 animals comprising 11 species of stranded and bycaught cetaceans in Hokkaido, Japan. Systemic amyloidosis was diagnosed in 2 out of 3 Stejneger’s beaked whales (Mesoplodon stejnegeri), through Congo red staining and immunohistochemistry for amyloid A. The kidney and gastrointestinal tract had the largest amounts of amyloid deposits, representing a previously undescribed organ distribution in the species. The current study demonstrates the possibility of Stejneger’s beaked whales being prone to the development of systemic amyloidosis, and highlights the need for further investigations.