Case A
open slide in the AHA AAPSP Digital Slide Server
History
A two-and-a-half-year-old bitch with a history of neurological and gastrointestinal signs
Example histopathological description
This is a 15 x 15 mm section of myocardium incorporating the epicardial and endocardial surfaces, showing multiple randomly distributed inflammatory aggregates, measuring to 2 mm, composed mainly of histiocytes with rare multinucleated giant cells. Surrounding these are light aggregates of lymphocytes and plasma cells. Within some lesions are central zones of lytic necrosis and the myocardial cells at the margins are swollen, with pyknotic nuclei and hypereosinophilic cytoplasm. Embedded within the inflammatory cell aggregates are numerous free and intracytoplasmic ovoid organisms that measure 5-15 x 10-20 μm. They have a thin colourless refractile cell wall, and a large amphophilic central body surrounded by a clear colourless halo. Occasionally, organisms show 4-8 wedge-shaped bodies separated by internal septa (endosporulation) which sometimes appear in a radial arrangement. There are some areas of subendocardial fibrosis within which are scattered siderocytes. The cell walls and cell bodies of the organisms selectively stained a deep pink using the PAS method.
Morphological diagnosis
Myocarditis, necro-granulomatous, chronic, multifocal, severe, with numerous intralesional algal-forms.
Aetiological diagnosis
This was a case of protothecosis (likely Prototheca zopfii).
Case B
open slide in the AHA AAPSP Digital Slide Server
History
Three-to-six-month-old goat kids, free-range grazing, with low incidence of hindlimb ataxia.
Example histopathological description
The slide consists of two transverse sections of spinal cord, including meninges and, in one section, attendant nerve rootlets. Based on the area and distribution of grey matter, the sections are considered likely representative of one lumbar and one thoracic segment.
In the white matter there is pronounced Wallerian degeneration, characterised by dilation of multiple individual nerve fibres, leaving in the majority of cases a conspicuous central axon surrounded by a clear space delimited by the nerve sheath. These changes are present in the myelinated fibres of the ventromedial and, to a lesser degree, the lateral funiculi. Lesions are most severe in the thoracic segment. In the lumbar segment the associated peripheral nerve shows occasional eosinophilic, enlarged axonal bodies.
In the grey matter, a high proportion of the neurones in the dorsal and ventral horns are enlarged with finely granular and poorly stained cytoplasm and loss of nuclei. Neurones are generally fading into the neuropil. Numerous neurones show central chromatolysis with the presence of homogenous, and in some cases hyalinised, neuroplasm and loss of Nissl substance. A low grade gliosis with increased numbers of microglia is present. Equivocal low grade satellitosis of occasional neurones is seen, however, there is no convincing evidence of neuronophagy. Longitudinal sections of nerve fibres in the nerve root show occasional enlarged eosinophilic bodies consistent with swollen axons.
Morphological diagnosis
Myelopathy, degenerative, chronic, multifocal, regionally severe, with prominent Wallerian degeneration.
Aetiological diagnosis
Enzootic ataxia (copper deficiency).