Disseminated Neosporosis in a dog
History: A 6 week-old intact female Boxer became non-ambulatory with decreased or absent hind limb reflexes. Forelimb and cranial nerve reflexes were normal. A Neospora titer was positive. There was acute onset of hind limb paresis in 3 out of 6 puppies in the litter.
Gross Pathology: None
Spinal cord: Diffusely throughout the spinal cord the spinal nerves and
ganglia are multifocally infiltrated by moderate numbers of lymphocytes,
macrophages, eosinophils and neutrophils with occasional protozoal
cysts consistent with Neospora caninum or Toxoplasma gondii. The
cysts measure 30-40 micron in diameter and contain numerous 2 X 4
micron zoites. There are multifocal areas of necrosis and gliosis in the
grey and white matter of spinal cord.
Brain: In all parts of the brain, but more prominently in the midbrain and
brainstem, there are multifocal areas of necrosis and gliosis with
occasional protozoal cysts in the neuropil, glial cells, or neurons. The
brain stem contains a bilaterally symmetrical area of neuronal necrosis
characterized by cell shrinkage, loss of nuclear detail, and
hypereosinophilia. There is central chromatolysis and peripheralization of
the nucleus in some neurons.
Sciatic nerve: There are multifocal interstitial infiltrates of eosinophilis,
lymphocytes, and macrophages.
Heart and skeletal muscle: There are multifocal interstitial infiltrates of
lymphocytes, macrophages, and a few eosinophils in the appendicular
skeletal muscle, glossal skeletal muscle, and myocardium.
1. Spinal nerves and ganglia: Polyradiculoneuritis and ganglionitis,
lymphocytic and eosinophilic, with intralesional protozoal cysts.
2. Brain and spinal cord: Encephalomyelitis, lymphocytic, histiocytic,
eosinophilic multifocal, moderate with intralesional protozoal cysts.
3. Sciatic nerve: Neuritis, eosinophilic and lymphocytic, multifocal,
4. Skeletal muscle,(appendicular, epaxial and glossal): Myositis,
multifocal, moderate, lymphocytic and eosinophilic
5. Heart: Myocarditis, lymphocytic, eosinophilic, multifocal, moderate
Neospora cannot be differentiated from Toxoplasma by light microscopy. Diagnosis of neosporosis is based on the positive serology for Neospora caninum and supportive histopathologic findings.
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