Disseminated central nervous system disease caused by Trypanosoma evansi in a horse.

Trypanosomiasis caused by Trypanosoma evansi ("Surra") is mainly a wasting disease affecting equids, camels and cattle as well as other domestic and wild animal species. In horses, infection may cause severe neurological abnormalities; however, the clinical progression, pathogenesis and molecular ante-mortem detection of this form of the disease have not been described in detail. A mare with progressive ataxia, head tilt, nystagmus and cranial nerve deficits submitted to treatment was diagnosed with central nervous system trypanosomiasis following the detection of a Trypanosoma tryposmastigote in cerebrospinal fluid cytology. Histopathology following necropsy showed that the brain, spinal cord and kidneys were the main affected tissues with disseminated multifocal non-suppurative meningoencephalitis of the central nervous system and membranoproliferative glomerulonephritis. Serology for T. evansi was positive and PCR indicated the presence of parasite DNA in the cerebellum, brain stem, spinal cord and bone marrow but not in other organs and confirmed the identity of causative agent as T. evansi. This is the first report of ante-mortem detection of T. evansi in the cerebrospinal fluid of a horse and the first description of post-mortem PCR identification of the parasite DNA in the nervous system.