Neospora caninum as causative agent of bovine encephalitis in Brazil.

For supporting the Brazilian bovine encephalitis surveillance program this study examined the differential diagnosis of Neospora caninum in central nervous system (CNS) by histological analysis (HE staining), immunohistochemistry (IHC), and nested-PCR using a set of primers from the Nc5 region of the genomic DNA and ITS1 region of the ribosomal DNA. A sample of 302 cattle presenting neurological syndrome and negative for rabies, aged 0 to 18 years, from herds in 10 Brazilian states was evaluated for N. caninum from January 2007 to April 2010. All specimens tested negative with IHC and nested-PCR using primers from the ITS1 region of ribosomal DNA, while two positive cases (0.66%) were found using primers from the Nc5 region of genomic DNA: a 20 month-old male and a 72 month-old female, both from São Paulo State. Only the male presented severe multifocal necrotizing encephalitis associated with mononuclear cell infiltration, a pathognomonic lesion caused by parasites of the family Sarcocystidae, and only this case was associated with N. caninum thus representing 0.33% positivity. Future studies should explore the association of IHC and nested-PCR with real-time PCR, a quantitative method that could be standardized for improving the detection of N. caninum in bovine CNS specimens.