Management of Behavioral Disorders in Zoo Primates: Two Cases at Melbourne Zoo
We review veterinary management of two cases of behavioral disorders affecting primates at Melbourne Zoo. Each case required that we develop a system for monitoring progression of disease and/or response to therapy, in order to guide management and outcomes.
Case 1: Delirium Post-Infarct in a Gorilla (Gorilla gorilla gorilla)
A 49-year-old female gorilla presented with acute onset of mental confusion, nystagmus, and bilateral upward gaze palsy. A neurocognitive deficit appeared likely, and differential diagnoses included development of a dementing illness and complications following transient ischemic incident (TIA). Over the next 12 weeks, clinical signs were monitored using simple tests that assessed social behaviors, short-term memory, thinking and planning ability, and awareness of environment. The tests suggested gradual improvement over a 3-month period, and a diagnosis of post-TIA delirium was made. At subsequent euthanasia, changes consistent with previous cerebral hemorrhages confirmed the diagnosis.1
Case 2: Anxiety Disorder in a Mandrill (Mandrillus sphinx)
A young male mandrill began demonstrating abnormal behaviors when two years of age. These increased in frequency and intensity, and included spinning, apparently involuntary limb movements, constant hand movements, and self-mutilation.
The clinical diagnosis was anxiety disorder with compulsive behaviors. The management plan included a training program focused entirely on rewarding calm behavior, enclosure modifications that allowed escape from any anxiety-inducing situations, and use of anti-anxiety medications (20 mg fluoxetine PO SID or 15 mg mirtazapine PO SID).
A simple monitoring system was used to assess response to therapy. The traffic signal system was based on a scale that may be used by children for emotional self-monitoring during cognitive behavior therapy.2 A “mood diary” provided basic assessment of overall anxiety level each day, and allocation of red (high intensity) days, amber (medium intensity) days and green (low intensity) days enabled keepers to monitor clinical progress over a nine-month period. The diary indicated that some clinical improvement had occurred during mirtazapine therapy. However, severe compulsive behaviors persisted at a high frequency. The mandrill was euthanized, having been assessed as having a poor quality of life.
1. Chiu E, Bodley K. A psychogeriatrician’s home visit to the zoo: a case report. Int Psychogeriatr. 2010;22:671–673.
2. Friedberg RD, McClure JM, Garcia JH. Cognitive Therapy Techniques for Children and Adolescents: Tools for Enhancing Practice. New York, NY: The Guildford Press; 2009.