Polioencephalomyelitis and neuronal necrosis caused by canine parvovirus-2a variant in free-ranging juvenile mountain lions ( <i>Puma concolor</i> )

Canine parvovirus 2a (CPV-2a) causes severe enteritis and diarrhea in unvaccinated domestic puppies and wild mesocarnivores, such as raccoons ( Procyon lotor ). A retrospective and prospective study was conducted to characterize CPV-induced encephalomyelitis in mountain lions ( Puma concolor ) from California. Four free-ranging juvenile mountain lions were euthanized due to severe neurological signs. Microscopically, multifocal neuronal necrosis, lymphoplasmacytic perivascular cuffing, and gliosis were primarily observed in the gray matter of the brain and spinal cord in all the studied animals. Rare intranuclear inclusion bodies were observed in the brainstem of 1 animal. All animals lacked microscopic and macroscopic evidence of enteritis. The association between the lesions and CPV-2 was confirmed by quantitative polymerase chain reaction (qPCR) and immunohistochemistry, which revealed the presence of viral DNA in nervous tissue and antigen in numerous necrotic neurons, respectively. Detection of CPV-2 mRNA by quantitative reverse transcription-PCR and nucleic acids by in situ hybridization indicated viral transcription in the necrotic neurons. Negative-contrast transmission electron microscopy revealed Parvoviridae particles in the brain, suggesting viral replication and assembly. Molecular sequencing in 2 cases detected a CPV-2a variant with amino acid substitutions previously observed in other wild carnivores. Although rare, CPV-2a is a potential cause of neurological signs in juvenile mountain lions without evidence of diarrhea or enteritis.