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Case report The clinical and laboratory findings in an orphaned juvenile female platypus (Ornithorhynchus anatinus) that presented with a severe anaemia and tick infestation are reported. The animal developed a terminal septicaemia and died. Antemortem clinical pathology, postmortem histopathology and 18S rDNA sequencing supported a diagnosis of extravascular haemolytic anaemia secondary to Theileria ornithorhynchi infection. Conclusion Although T. ornithorhynchi infection is common in the platypus, this is the first case in which it has been shown to cause a haemolytic anaemia in this species and molecular characterisation of the organism has been described. A review of the previous literature concerning T. ornithorhynchi and possible treatment options for future cases are discussed.

Objective To determine whether there are haematological, serum biochemical and serological differences between platypuses (Ornithorhynchus anatinus) with and without granulomatous dermatitis due to Mucor amphibiorum infection. An additional objective was to establish reference haematological and serum biochemical ranges for the species in Tasmania. Design A clinicopathological and serological study. Animals A total of 37 free-living adult platypuses captured from streams and dams in Northern Tasmania were used in the clinicopathological study. Twenty-seven were clinically normal and 10 had mycotic granulomatous dermatitis. A total of 22 platypuses (20 adult and 2 juvenile) were used for the serosurvey. Eighteen were captured from streams in Northern Tasmania, and four were submitted for necropsy. Results Platypuses with mycotic ulcerative dermatitis had significantly smaller packed red cell volumes, haemoglobin concentrations, lymphocyte counts, serum cholesterol and calcium concentrations, and higher serum globulin and potassium concentrations than clinically normal animals. The lymphopenia and hyperkalaemia were thought to be clinically significant. Numbers of Trypanosoma binneyi in blood smears were similar between the two groups. Diseased platypuses had higher concentrations of serum antibody against Mucor amphibiorum as determined by ELISA compared to clinically normal platypuses. Conclusion Platypuses affected by mycotic granulomatous dermatitis showed haematological and serum biochemical changes when compared to clinically normal animals from the same Tasmanian sites. A serological survey may be a useful method for detecting the prevalence of exposure to Mucor amphibiorum and humoral immunity in platypus populations both in Tasmania and the mainland of Australia.

The gross and histological appearance and the distribution of T and B lymphocytes and plasma cells are described for lymphoid tissues obtained from 15 platypuses. The spleen was bilobed and surrounded by a thick capsule of collagen, elastic fibres and little smooth muscle. White pulp was prominent and included germinal centres and periarterial lymphoid sheaths. Red pulp contained haematopoietic tissue. A thin lobulated thymus was located within the mediastinum overlying the heart. The cortex of lobules consisted of dense aggregates of small and medium lymphocytes, scattered macrophages and few reticular epithelial cells. In the medulla, Hassall's corpuscles were numerous, lymphocytes were small and less abundant, and reticular cells were more abundant than in the cortex. Lymphoid nodules scattered throughout loose connective tissue in cervical, pharyngeal, thoracic, mesenteric and pelvic sites measured 790 +/- 370 microm (mean +/- S.D., n = 39) in diameter, the larger of which could be observed macroscopically. These consisted of single primary or secondary follicles supported by a framework of reticular fibres. Macrophages were common in the germinal centres. The platypus had a full range of gut-associated lymphoid tissue. No tonsils were observed macroscopically but histologically they consisted of submucosal follicles and intraepithelial lymphocytes. Peyer's patches were not observed macroscopically but histologically they consisted of several prominent submucosal secondary follicles in the antimesenteric wall of the intestine. Caecal lymphoid tissue consisted of numerous secondary follicles in the submucosa and densely packed lymphocytes in the lamina propria. Bronchus-associated lymphoid tissue was not observed macroscopically but was identified in 7 of 11 platypus lungs assessed histologically. Lymphoid cells were present as primary follicles associated with bronchi, as aggregates adjacent to blood vessels and as intraepithelial lymphocytes. The distribution of T lymphocytes, identified with antihuman CD3 and CD5, and B lymphocytes and plasma cells, identified with antihuman CD79a and CD79b and antiplatypus immunoglobulin, within lymphoid tissues in the platypus was similar to that described in therian mammals except for an apparent relative paucity of B lymphocytes. This study establishes that the platypus has a well-developed lymphoid system which is comparable in histological structure to that in therian mammals. It also confirms the distinctiveness of its peripheral lymphoid tissue, namely lymphoid nodules. Platypus lymphoid tissue has all the essential cell types, namely T and B lymphocytes and plasma cells, to mount an effective immune response against foreign antigens.

Objective Correlation of immunophenotype with history, anatomical and morphological features of lymphoid neoplasia in the koala. Methods Routine necropsies were performed on 51 koalas with suspected lymphoid neoplasia between 1986 and 1997 in New South Wales and Queensland. Immuno-phenotyping was by an immunoperoxidase method utilising species cross-reactive antibodies raised against human lymphocytes and an antibody raised against koala IgG. Cases were classified according to organs and tissues affected and the morphological features of neoplastic cells. Results Twenty-six (51%) of the cases were of the T cell immunophenotype, 12 (24%) were of B cell immunopheno-type and 13 (25%) did not stain. The age and sex of koalas did not correlate with immunophenotype (P = 0.686 and P = 1.000, respectively). Thirty-two cases were leukaemic and 36 had multiple organ involvement, probably reflecting presenta tion of koalas at advanced stages of disease. Abdominal tissue involvement was most common (44 cases), followed by nodal (32), atypical (21) and cervicomediastinal (14). The T cell immunophenotype was over-represented among the leukaemic cases (P = 0.013). Generally, the T cell immunophenotype predominated except for many affected atypical tissues. Neoplastic cells were mostly of medium nuclear size with round to oval nuclei. No correlations were found for cell morphology, mitotic index and immunopheno-type. Conclusion The prognostic value of an immunopheno-typic, anatomical and morphological basis for the classifica tion of lymphoid neoplasia in the koala currently is limited by the need to detect these neoplasms at an early age, the requirement for freshly fixed tissues and the restricted range of available cross-reacting antibodies.