Cerebrospinal fluid changes in cattle with rabies or with BoHV-5 meningoencephalitis and its correlation with the severity of CNS inflammatory process

The objective of this study was to describe and compare the changes in the cerebrospinal fluid (CSF) of cattle affected by rabies or BoHV-5 meningoencephalitis and correlating them with the severity of central nervous system (CNS) inflammation. Samples of CSF and CNS tissues from cattle naturally infected with rabies virus (n = 17) and BoHV-5 (n = 17) were examined. Histologically, meningitis was classified according to the type and quantity of inflammatory cells. The lesions observed in the brain parenchyma and in the spinal cord that defined the presence of inflammatory process were perivascular cuffs, gliosis and glial nodules. CSF mononuclear pleocytosis and high protein concentration were present in both diseases, but 47% of rabies cattle had no changes, and the median number of leukocytes was 5.4 fold higher (p < 0.001) in cattle affected by BoHV-5 meningoencephalitis. In both diseases, the histopathological changes were characterized by non-suppurative meningoencephalitis. The presence and severity of the lesions varied, in each disease; however, the inflammatory process was less severe in rabies. The number of leukocytes and the protein concentration presented in the CSF were correlated with each other (r = 0.497, P = 0.013), and correlated well with the intensity of meningitis in the telencephalon and with the severity of inflammatory process in the cerebral cortex parenchyma. It can be concluded that in rabies, the CSF may not change or may exhibit discrete mononuclear pleocytosis and/or mild elevated protein within the CSF. In BoHV-5 encephalitis, these changes are always present and more pronounced, as a result of the more severe inflammatory process in cerebral meninges and parenchyma.