Causes of Encephalitis and Encephalopathy in Brazilian Equids

The etiology of diseases that affect the central nervous system (CNS) of equids was investigated. Samples (n = 218) collected from equids showing clinical signs of nervous or behavioral changes were analyzed, of which 37 (17.0%) were positive for rabies, 13 (6.0%) for the presence of protozoans (one Sarcocystis neurona, 12 Toxoplasma gondii), three (1.4%) for equine herpesvirus type 1 myeloencephalopathy, and 24 (11%) for bacterial encephalitis. Histopathology of the CNS revealed one (0.4%) case of cryptococcal myelomeningoencephalitis and 20 (9.2%) cases of equine leukoencephalomalacia. Central nervous system samples were positive for Sarcocystis neurona and Toxoplasma gondii by nested PCR-ITS1 followed by nucleotide sequencing. Diagnosis of equine herpesvirus 1 was confirmed by cell isolation and polymerase chain reaction followed by sequencing of the GD and polymerase (ORF 30) genes in three samples. No case of equine encephalomyelitis was diagnosed in samples analyzed by isolation in mice, VERO cell cultures, and RT-PCR for the nsP1 gene. Bacterial agents (Staphylococcus spp., Streptococcus spp., Bacillus spp., Enterobacteriaceae spp., Corynebacterium spp., and nonfermenting gram-negative bacillus) were detected in pure or preponderant cultures. Diagnosis was conclusive in 45% of samples, indicating that other infectious and noninfectious etiologies of encephalitis and encephalopathy should be considered for investigation.