Histopathological and molecular characterization of encephalitic listeriosis in small ruminants from northern Paraná, Brazil

Listeriosis is a disease primarily of ruminants caused by the Gram-positive bacterium Listeria monocytogenes. Ruminants either demonstrate manifestations of the encephalitic, septicemic, or re-productive form of listeriosis. The pathological and molecular findings with encephalitic listeriosis in a 5.5-month-old, male, mixed-breed goat and a 3-year-old Texel-crossed sheep from northern Paraná, Brazil are described. Clinically, the kid demonstrated circling, lateral protrusion of the tongue, head tilt, and convulsions; the ewe presented ataxia, motor incoordination, and lateral decumbency. Brainstem dysfunctions were diagnosed clinically and listeriosis was suspected. Necropsy performed on both animals did not reveal remarkable gross lesions; significant histopatho-logical alterations were restricted to the brainstem (medulla oblongata; rhombencephalitis) and were characterized as meningoencephalitis that consisted of extensive mononuclear perivascular cuffings, neutrophilic and macrophagic microabscesses, and neuroparenchymal necrosis. PCR assay and di-rect sequencing, using genomic bacterial DNA derived from the brainstem of both animals, amplified the desired 174 base pairs length amplicon of the listeriolysin O gene of L. monocytogenes. Phylo-genetic analyses demonstrated that the strains associated with rhombencephalitis during this stud