Pathology in Practice

Pathology in practice: case report of a Young dog affected by CNS neosporosis. The case report is described according to the modalities of "what is your diagnosis". A young adult 12-kg (26.4-lb) female mixedbreed dog housed in an animal shelter was referred to the teaching hospital of the Department of Veterinary Medical Sciences of the University of Bologna because of severe nonambulatory tetraparesis and abnormal mentation. The dog was found wandering 2 months before; at that time, the dog had mild paraparesis that slowly progressed to tetraparesis and recumbency. On neurologic examination, the dog was in lateral recumbency with severe nonambulatory tetraparesis, obtunded mental status, leftsided head tilt, occasional tremors of the neck and head, and spontaneous proprioceptive deficits in all 4 limbs. Cranial nerve examination revealed vertical spontaneous nystagmus and an abnormal menace response. History and clinical signs were consistent with a suspected multifocal neurologic disorder, primarily involving the brainstem. Serum and CSF samples were tested for antibodies against Toxoplasma spp and Neospora spp. Both samples were negative for Toxoplasma spp but strongly positive for Neospora spp (in both samples, the IgG titer was 1:640 (reference interval applied to both serum and CSF, < 1:40). A PCR assay was performed on the CSF sample, and the result was positive for Neospora caninum. On post mortem examination, sections of the brain (cerebral cortex) revealed that neuroparenchyma was affected by multifocal malacia and reactive gliosis associated with intralesional groups of protozoa; numerous deeply basophilic bradyzoites measuring 6.5 X 1.5 μm were present, often within the cytoplasm of glial cells. There was evidence of nonsuppurative lymphoplasmacytic meningoencephalitis and reactive gliosis; samples of the cerebellum and brainstem contained scattered cysts without septa, with a wall thickness of 0.5 to 4 μm. Ultrastructural examination of brain and cerebellum revealed bradyzoites grouped together and not enclosed by a cyst wall; intact bradyzoites had an apical part (conoid) rich in micronemes, rhoptries with an electron-dense content, electron-lucent amylopectin granules, and a nucleus , supporting the etiologic diagnosis of neosporosis.