Cerebellar Hypoplasia in Two Juvenile African Grey Parrots (Psittacus erithacus).

Abstract

Two sibling 12-week-old DNA-sexed female African grey parrots (Psittacus erithacus) were presented for progressive whole-body tremors, proprioceptive deficits, and an inability to stand unassisted. A third bird in the clutch (DNA-sexed as a male) exhibited no clinical signs. Physical examination of the affected birds revealed ataxia, inability to stand without assistance, and a reliance on their beaks to assist with their mobility. Hematologic and biochemical analyses were normal, as were radiographic images of both birds. Cerebellar disease of unknown origin was diagnosed, and the birds were euthanized. Postmortem examinations of the brains of both parrots revealed marked reduction in cerebellar size and poor folia formation. Microscopic review of the cerebellums demonstrated decreased density of the granular layer and thinning of the molecular layer with poorly organized and differentiated Purkinje fibers, consistent with a diagnosis of cerebellar hypoplasia. There are limited clinical reports and experimental studies examining cerebellar disease in birds. Conditions described have included cerebellar hypoplasia, cerebellar abiotrophy, and cerebellar dysplasia. Although these terms are used interchangeably due to similar clinical signs, histopathology is needed to differentiate between the different disease conditions. This case describes cerebellar hypoplasia that suggested a developmental etiology in 2 African grey parrots.