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United States Department of Agriculture

Agricultural Research Service

Title: Neospora Caninum-Associated Equine Protozoal Myeloencephalitis

Authors
item Hamir, A - OREGON STATE UNIVERSITY
item Tornquist, S - WALTER REED WASHINGTON DC
item Gerros, T - OREGON STATE UNIVERSITY
item Topper, M - WALTER REED WASHINGTON DC
item DUBEY, JITENDER

Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 15, 1998
Publication Date: N/A

Interpretive Summary: Neospora caninum is a recently recognized protozoan (single-celled) parasite of animals. It causes abortion in livestock and paralysis in companion animals. Although N. caninum infection is common in cattle and dogs, little is known of its prevalence in other animals. Scientists at the Beltsville Agriculture Research Center and the Oregon State University report a case of encephalitis in a horse and distinguish it from another parasite Sarcocystis neurona which is a common cause of neurologic disease in the horse. These results will be of use to parasitologists, veterinarians and equine practioners.

Technical Abstract: Equine protozoal myeloencephalitis (EPM) was clinically diagnosed in a 20- year-old horse with severe ataxia. The cerebrospinal fluid was positive for Sarcocystis neurona antibodies by western blot. The horse was administered corticosteroids to facilitate invitro culture of S. neurona from its spinal cord following necropsy. Microscopic lesions of EPM were present in the brain and the spinal cord, including multifocal inflammator cellular infiltrates and several large groups of protozoa. Immunohistochemical, and light and electron microscopic examinations revealed that the protozoa was Neospora caninum and not S. neurona. The protozoa divided by endodyogeny, tachyzoites had rhoptries, and organisms reacted specifically to N. caninum antibodies. Veterinarians should be aware of increasing diagnosis of N. caninum as another etiological agent responsible for the lesions of EPM.

Last Modified: 9/10/2014
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