Molecular characterization of encephalitic bovine listeriosis from southern Brazil.

Reports of bovine listeriosis in Brazil are uncommon, being restricted to citations within retrospective studies, resulting in scarce documented information of this important disease of cattle. This manuscript describes the molecular findings associated with spontaneous encephalitic listeriosis in two steers from distinct herds within the state of Paraná, southern Brazil. Both animals demonstrated altered consciousness suggestive of brain stem dysfunctions and died a few days after the initial onset of disease. Polymerase chain reaction (PCR) assays were designed to target specific genes of infectious neurological agents of cattle. These included bovine herpesvirus 1 and 5 (BoHV-1 and BoHV-5), ovine herpesvirus 2 (OvHV-2), Listeria monocytogenes, and Histophilus somni. Rabies virus was discarded in evaluations done at the official state diagnostic laboratory. Gross alterations were insignificant; histopathology demonstrated rhombencephalitis associated with macrophage-predominant, multifocal to coalescing microabscesses and extensive perivascular cuffings in both steers. The L. monocytogenes PCR assay amplified the 172-bp amplicon of the listeriolysin gene from the brain stem of both animals and from the telencephalon, thalamus, and cerebellum of one of them. Phylogenetic analyses demonstrated that the strains derived from this study clustered with known strains of L. monocytogenes lineage I. The BoHV-1 and BoHV-5, OvHV-2, and H. somni PCR assays were negative. These results confirm the participation of L. monocytogenes lineage I in the etiopathogenesis of the neurological disease herein described and represent the first complete description of encephalitic listeriosis in cattle from Brazil.