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Keywords:

  • Ataxia;
  • Cerebellum;
  • Labrador Retriever;
  • Masticatory myositis;
  • Neosporosis

Background: Adult dogs with neosporosis can develop a variety of neurologic signs. No area of predilection within the nervous system so far has been identified in adult dogs.

Objectives: To document neosporosis as a cause of progressive cerebellar ataxia and cerebellar atrophy in dogs.

Animals: Seven client-owned dogs.

Methods: Retrospective, descriptive study.

Results: Age at diagnosis ranged from 1 year 6 months to 9 years 11 months. Neuroanatomic localization indicated cerebellar and brainstem disease in 6 dogs and a central vestibular lesion in 1 dog. In all 7 dogs, there was moderate to marked bilaterally symmetrical cerebellar atrophy, with the atrophied cerebellum being surrounded by a region of T2-weighted hyperintense and T1-weighted hypointense signal. Cerebrospinal fluid (CSF) analysis in all but 1 dog showed mononuclear pleocytosis and high protein concentration. Polymerase chain reaction testing for Neospora caninum performed on the CSF was positive in 4/5 dogs tested and there was a high titer of serum antibodies to N. caninum (≥ 1 : 800) in all 6 dogs tested. Postmortem examination in 1 dog confirmed cerebellar atrophy and multifocal nonsuppurative encephalitis with areas of malacia and leptomeningitis. All of the remaining 6 dogs were treated with some combination of clindamycin, trimethoprim, sulfadiazine, and pyrimethamine. Two dogs were euthanized because of deterioration or relapse of neurologic signs, but treatment of the remaining 4 dogs resulted in improvement (3 dogs) or resolution (1 dog) of neurologic signs.

Conclusions and Clinical importance: Neosporosis is an important cause of progressive cerebellar ataxia and cerebellar atrophy in adult dogs.