The aim of these studies was to obtain more detailed information on the occurrence and distribution of amyloidosis in captive and wild birds, to analyse the relationship of amyloidosis to other diseases and influential factors, and to characterize the avian amyloid protein histochemically and immunohistochemically. The studies were performed at the Institute for Zoo and Wildlife Research in Berlin. Their basis were post-mortem reports and a diversity of organ specimens embedded in paraffine wax from birds autopsied between 1970 and 1992. The post-mortem reports on 8456 autopsied birds belonging to 23 avian orders were analysed in the first part of this study. All records on birds with the diagnose amyloidosis were evaluated in relation to species, sex, date of death, accompanying diseases and causes of death. The object of the second part of this study was to performe a histochemical and immuno-histochemical characterization of the amyloid protein. For the histochemical examinations the potassium permanganat reaction (WRIGHT et al., 1977) was used on 100 selected birds from 13 orders. This method is suitable for distinguishing the amyloid protein AA from other varieties of amyloid on the basis of a strongly reduced or lost Congo red binding after exposure to potassium permanganate. For this distinction, tissue sections pretreated with potassium permanganat were stained with Congo red and compared with parallel sections without potassium permanganat exposure. Amyloid was considered permanganat-sensitive (and identified as amyloid AA protein) if all amyloid deposits present in the tissue section totally or nearly totally (with more than 90 % loss) lost their Congo red affinity. The immuno-peroxidase technique (with diaminobenzidine as the chromogen) was used for immuno-histochemical characterization of the amyloid protein on 50 selected birds from 13 orders. As primary antibodies a commercially available monoclonal human anti-AA antibody and a polyclonal rabbit anti-duck amyloid-A antibody were applied. By using appropriate controls, all deposits in the tissue sections showing a light to dark brown colour were identified als amyloid-A positive. The results of these examinations can be summarized as follows:
1. In partial confirmation of studies performed by other authors the avian orders Anseri-formes, Phoenicopteriformes, Gruiformes and Charadriiformes were shown to be especially prone to amyloidosis. Differences in the incidence of amyloidosis were found also among families, genera and tribes within these orders. 2. According to the results of these studies, the somewhat higher incidence of amyloid occurence in winter and spring, as compared with the summer and autumn months, can not be considered as evidence for a true seasonal variation, as it was claimed by some other authors. In considering the age of the birds, a distinctly higher proportion of young birds with a very low incidence of amyloidosis was generally autopsied in summertime as compared to wintertime. In addition, beginning and course of amyloidosis can not be determined at autopsy due to the chronicity of this disease. Taking into account all these circumstances, a seasonal character of amyloidosis with a peak value in winter and spring can not reliably be demonstrated with certainty. 3. Avian amyloidosis occurred as so-called secondary form associated with chronic diseases or inflammations in the majority of cases. Idiopathic amyloidosis without a recognizable accompanying disease was found in 28,4 % of all cases. According to present knowledge, the two formes can be identified as a reactive amyloidosis which seems to be caused by the same or a similar pathogenetic mechanism. 4. The distribution pattern of the amyloid deposits is consistent with that of the systemic amyloidosis. Amyloid deposits occurred in more than one organ in most cases. Primarily involved were liver, spleen and kidneys. 5. According to the histochemical and immunohistochemical studies the avian amyloid examined belongs to the type AA. That means that the amyloid fibrils are derived from the acute phase protein SAA in all cases.
In conclusion, it can be stated that all cases of amyloidosis in birds hitherto examined are of the reactive type or type AA.
