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.