Case A
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History
Backyard chicken with a history of being unable to stand.
Example of histopathological description
There are two portions of peripheral nerve surrounded by condensed collagenous tissue, perineurium and connective tissue. In each nerve there are marked, multifocal and coalescing, densely cellular infiltrates of mononuclear cells which separate, dissect and disrupt the nerve fibres. The mononuclear cells are predominantly lymphoid, often with small and mature lymphocytes together, and include lower numbers of plasma cells. Less frequently there are multifocal areas of large lymphoblastic cells. The latter have small amounts of cytoplasm, large nuclei, coarsely stippled chromatin and indistinct nucleoli. The mitotic rate is 1 to 2 per 10 high power fields. Within each nerve, proteinaceous oedema is separating and expanding the space between fibres. There are occasional swollen sheaths containing axons and infrequently, acidophilic fibrillar material consistent with small fragments of myelin. In the surrounding connective tissue stroma of the perineurium there are mild multifocal and segmental infiltrates of macrophages, heterophils and occasional degenerate adipocytes.
Morphological diagnosis
Peripheral neuritis, lymphocytic, subacute, diffuse, moderately severe with axonal degeneration.
Aetiology
Gallid Herpesvirus 2 (GAHV-2) also known as Marek’s disease virus (MDV).
Case B
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History
Feral rabbit necropsied and suspected tumours reported by the submitting vet.
Example histopathological description
In this section of liver there is multifocal to diffuse adenomatous dilation of the biliary tree with severely hyperplastic epithelium forming papillary projections, associated with intracellular coccidial organisms. There are macrogametes, microgametes and intraluminal cellular debris with myriad refractile parasitic oocysts. The macrogametes are round, 20-50 µm in diameter with a central nucleus, prominent nucleolus, and brightly eosinophilic 3-4 µm peripheral granules. The microgametes are round, 15-25 µm in diameter with peripheral, lightly basophilic, granules. The unsporulated oocysts measure 20-40 µm in diameter with thick refractile walls that are often collapsed and contain lightly basophilic, granular cytoplasm with a nucleus. The affected bile ducts demonstrate minimal connective tissue proliferation and mild infiltrations of lymphocytes, plasma cells, macrophages and degenerate heterophils. A single affected bile duct has lost epithelial integrity and is filled with haemorrhage and remnant parasitic oocysts. Mild lymphocytic infiltrates are present in unaffected portal tracts. Hepatocytes show moderate glycogen vacuolation.
Morphological Diagnosis
Cholangiohepatitis with severe biliary ectasia and papillary hyperplasia, chronic, multifocal, severe, with numerous intraepithelial and intraluminal coccidian parasites consistent with Eimeria stiedae.
Comments
This condition is referred to as hepatic coccidiosis due to Eimeria stiedae infection. The lesions may resemble tumours grossly. It should be noted that hepatic coccidiosis may predispose rabbits to the development of cholangiocellular carcinomas.