Parkinsonian-Like Presentation of Nonsuppurative Encephalitis in a Juvenile White-Handed Gibbon (Hylobates lar)
Neurologic disease is frequently reported in gibbons anecdotally, and this case details a 21-month-old female white-handed gibbon (Hylobates lar) that presented with Parkinsonian-like signs in July 2017. Contrast magnetic resonance imaging (MRI) demonstrated signal abnormalities of the caudate nucleus consistent with viral encephalitis. West Nile Virus serum neutralization (SN) titers at 1, 10, 18, and 27 weeks post-onset of clinical signs were <4, 96, 128, and 192, respectively. The gibbon became progressively weaker despite oral prednisone and phenobarbital. Nineteen weeks following the onset, the gibbon sustained a severe soft tissue injury to the left pelvic limb with loss of motor function and superficial pain. Steroid therapy was re-initiated, in addition to amantadine (3.2 mg/kg PO SID). Amantadine, an antiviral drug frequently used in treatment of Parkinson’s disease in humans, has been demonstrated to significantly reduce viral RNA levels of West Nile Virus in vitro.1 While the intention tremors resolved, electromyography (EMG) and repeat MRI were performed in March 2018 due to progressive weakness and development of epilepsy minimally controlled with clonazepam and levetiracetam. Electromyography was unremarkable; however, atrophy of the cortex, thalamus and cerebellum were noted on MRI. Humane euthanasia was elected. Histopathology of the brain demonstrated moderate nonsuppurative encephalitis in the cerebrum and glial scarring with axonal degeneration in the caudate nucleus and white matter tracts of the cerebellum, consistent with chronic but active inflammation. Further testing is pending to rule out possible infectious etiologies such as West Nile Virus, Baylisascaris spp., Toxocara spp., Toxoplasma spp., and Sarcocystis neurona.
The authors would like to thank the pediatric neurology department at Riley Hospital for Children at Indiana University Health, Randall Johnny Cross DVM Dipl ACVIM, Andrea Sangster DVM Dipl ACVIM, Katharine Hope DVM Dipl ACZM, and Emily Talaga DVM CCRP (Rehabilitation) for their guidance and insights with case management. In addition, the histopathologic interpretation by Dr. Michael Garner DVM Dipl ACVP has provided invaluable insight. They further thank the Polly Horton Hix Animal Care Complex staff, especially Meghann Sachs and Pete Peterson, for their dedicated daily care of this patient.
1. Blazquez AB, Martin-Acebes MA, Saiz JC. Inhibition of West Nile virus multiplication in cell culture by anti-Parkinsonian drugs. Front Microbiol. 2016;7:296.