Pathological study on amyloidosis in Cygnus olor (mute swan) and other waterfowl

Between 2004 and 2007, we examined a total of 70 waterfowl. Forty of 51 (78.4%) mute swans (Cygnus olor) had amyloidosis. Amyloid deposits were detected in the spleen of 39 of 49 birds (79.6%), liver of 37 of 47 birds (78.7%), intestine of 38 of 50 birds (76.0%), pancreas of 30 of 42 birds (71.4%), kidney of 32 of 47 birds (68.1%), thyroid gland of 20 of 30 birds (66.7%), heart of 26 of 49 birds (53.1%), and lung of 5 of 45 birds (11.1%). In some birds, there was a globular pattern of amyloid deposition or infiltration of foreign-body giant cells around amyloid nodules in the spleen. Immunostaining with anti-AA antibody and Western blotting revealed that all were cases of AA amyloidosis. In sections treated with potassium permanganate, which removes Congo red stain, the green refringence under polarized light had mostly vanished. However, staining was not completely eliminated in some areas. Electron microscopy confirmed that the star-shaped amyloid fibrils were 10 nm in diameter and lacked branching. We also demonstrated amyloid bundles and star-shaped amyloid fibrils. A high percentage (96.3%) of mute swans had an inflammatory condition known as bumblefoot. Swans are useful model for studies of animals that have high amounts of amyloid. This research may help in the elucidation of the mechanism of amyloidogenesis in humans, and more research regarding amyloidosis in birds that are consumed as food is necessary.