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

Comparison of carbon, nitrogen, and oxygen stable isotope ratios and mercury concentrations in muscle tissues of five beaked whale species and sperm whales stranded in Hokkaido, Japan

We studied δ13C, δ15N and δ18O values, and total mercury (THg) concentrations in muscle samples from deep-sea predators - five beaked whale species and sperm whales - stranded along the coast of Hokkaido, in the north of Japan in 2010 and 2019. The δ13C, δ15N and δ18O values, THg concentrations, and body length (BL) of Stejneger's beaked whales were similar to those of Hubbs' beaked whales, which belong to the same genus. In contrast, δ13C values, THg concentrations, and BL of Sato's beaked whales were markedly different from those of Baird's beaked whales, which belong to the same genus. Stejneger's and Hubbs' beaked whales living around Hokkaido may compete in their ecological niches, whereas Sato's and Baird's beaked whales may segregate their ecological niches. Although Cuvier's beaked whales and sperm whales belong to different genera and their BLs were significantly different, their δ13C and δ15N values were similar, probably because they can dive and stay in deeper waters than other beaked whale species. The δ13C values in combined samples from all whales increased with increasing BL, probably owing to the larger whale species' dietary preference for squid. The δ13C values in combined samples from all whales were positively correlated with THg concentrations, whereas the δ15N values in the combined samples were negatively correlated. The δ18O values in combined samples from most whales tended to be positively correlated with THg concentrations. These correlations may be explained by a higher THg load from deep-sea feeding than from pelagic feeding and by a feeding shift towards lower trophic levels.

Carbon, nitrogen, and oxygen stable isotope ratios of striped dolphins and short-finned pilot whales stranded in Hokkaido, northern Japan, compared with those of other cetaceans stranded and hunted in Japan

Strandings of striped dolphins (SD) and short-finned pilot whales (PW) in Hokkaido, northern Japan, are rare but have recently increased, probably due to global warming. We quantified δ13C, δ15N, and δ18O in muscles of SD (n = 7) and PW (n = 3) stranded in Hokkaido and compared these values with those in muscles (red meat products) of hunted SD and PW in three areas of central and southern Japan. δ18O in stranded SD, except for the calf, decreased with increasing body length (BL), whereas δ13C increased, with no BL-related changes in δ15N. The variability of δ18O (range of maximum and minimum) was larger in the stranded SD (7.5 ‰) than of the hunted SD in three areas (0.9, 1.9, and 1.4 ‰), whereas that of δ15N was smaller in the stranded SD than in the hunted SD. Similarly, the variability of δ18O was larger in the stranded PW in Hokkaido (3.3 ‰) than in the hunted PW in central Japan (1.4 ‰). The larger variability of δ18O and smaller variability of δ15N in stranded SD imply long-term sojourning in coastal waters and feeding on small amounts of limited prey species at low trophic levels before death.

Survey of amyloidosis cases among different free-living wild and zoo animals

Amyloidosis comprises a range of protein-folding disorders characterised by a buildup of amyloid deposits in one or multiple organs. The pathogenesis and pathologic findings of amyloidosis can vary widely due to the nature of the precursor protein. In veterinary medicine, there are 10 proteins known to form amyloid deposits in various organs. This review aims to compare amyloidosis cases among different free-living wild and zoo animals focussing in part on the determination of the species particularly susceptible to the amyloid formation and specific prone-to-aggregate protein commonly involved. This review addresses the transmission of AA amyloidosis pertinent to institutions, such as zoos, housing multiple individuals and species in relatively close proximity. In addition, this review includes summarisation for definitive diagnosis of single or multiple cases of amyloidosis affecting free-living wild and zoo animals. Insights into the diversity, transmission, and pathogenesis of known amyloidogenic proteins and species prevalently affected may help to establish a preventive intervention and stimulate the discovery of new diagnostic and therapeutic strategies.

Histochemical and Immunohistochemical Characterizations of Hepatic Trematodiasis in Odontocetes

Hepatic trematodiasis is a common condition in a number of free-ranging cetacean species, which occasionally result in severe hepatic and/or pancreatic lesions. However, even the basic pathological information of this disease is unknown for the majority of affected species. The current study describes and compares the histomorphology and immune reaction induced by hepatic trematodes of the family Brachycladiidae in the liver of the harbor porpoise (Phocoena phocoena, n = 8), Dall's porpoise (Phocoenoides dalli, n = 8), and Hubbs' beaked whale (Mesoplodon carlhubbsi, n = 2). Immunohistochemistry for eight antibodies (CK19, CD3, Foxp3, CD20, Iba1, CD68, CD163, and CD204) was conducted to analyze the pathology of these parasitic infections. In all three odontocete species, the changes observed in the trematode-affected biliary epithelium were comparable with marked hyperplasia and goblet cell metaplasia, as well as lymphoplasmacytic and eosinophilic inflammation. Additionally, regions of the Glisson's sheath were diffusely and severely fibrotic in all examined species, regardless of the physical presence of trematodes. Differences among the three species included the presence of characteristic lymphoid follicles formed in the fibrotic bile duct walls of only the two porpoise species. In the Hubbs' beaked whale, the degree of lymphoplasmacytic cholangitis was more severe, and ductular reaction was generally more prominent. In terms of the overall macrophage population among the three species, CD163- and CD204-positive cells (M2 macrophages) outnumbered Iba1- and CD68-positive cells (M1 macrophages), indicating a chronic infection stage in all analyzed individuals. Species-specific differences among the infiltrating macrophages included numbers of CD68-positive cells being significantly more abundant in the harbor porpoises, whereas CD163-positive cells were significantly more numerous in the Dall's porpoises. The numbers of CD204-positive macrophages were higher in the Hubbs' beaked whales compared to those in the porpoises. Trematode species of the harbor and Dall's porpoises were Campula oblonga, while they were Oschmarinella macrorchis in the Hubbs' beaked whales. This study concludes that interspecies differences in the tissue reactions to hepatic trematode infections are present among odontocete species and that the immune reaction varies depending on the species. This information aids in furthering our understanding of the pathogenesis of hepatic trematodiasis in cetaceans.

Systemic Amyloid A Amyloidosis in Stejneger's Beaked Whales (Mesoplodon stejnegeri)

Stejneger's beaked whales (Mesoplodon stejnegeri) are one of the lesser known species of mammals, with little information available on their population status or incidence of diseases. Recent pathologic investigations on stranded and bycaught wild cetaceans around Hokkaido, Japan, revealed an unusually high incidence of systemic amyloidosis in this species, warranting further investigation. The objective of this study was to further characterize the systemic amyloidosis of Stejneger's beaked whales by retrospective histopathologic analyses of tissues from animals that stranded in Japan between 1994 and 2018. Various tissues from 35 individuals were examined histologically with hematoxylin and eosin, Congo red, and immunohistochemistry for amyloid A (AA), in which 12 (34%) were diagnosed with systemic amyloidosis. The organs with the highest severity of amyloid deposition were the stomach and intestine. The type of amyloid was confirmed as AA of approximately 9 kDa by 2-dimensional gel electrophoresis with extracted amyloid from the liver and subsequent Western blotting with an antiserum against AA peptide. There were no statistically significant associations between amyloidosis and sex, body condition of the whales, or the presence of chronic inflammation. The high prevalence of this disease might be of concern for overall population numbers, and continued pathologic monitoring of stranded animals is necessary throughout its distributional range.