Gangliosidosis in emus (Dromaius novaehollandiae)

A 6-month-old female emu (Dromaius novaehollandiae) died following acute central nervous system signs. Hematoxylin-and-eosin-stained sections revealed that neurons of the brain were distended with nonstaining 1-to-2-microns vacuoles. Ultrastructural examination of the affected neurons revealed numerous membranous cytoplasmic bodies (MCBs) similar in appearance to the MCBs seen in mammalian gangliosidoses. A full sibling of this emu was donated for study. This 7-month-old female emu was stunted compared with hatchmates. Neurologic examination revealed hypermetric gait, persistent head tremor, and mild ataxia. No gross lesions were evident at postmortem. Histopathologic and electron microscopic findings were similar to those in the index case in that swollen, pale neurons were present in the cerebrum, pons, medulla, cerebellum, spinal cord, spinal ganglia, autonomic ganglia, myenteric plexus, and ganglion cell layer of the retina. Analysis of brain gangliosides of the affected 7-month-old emu revealed 14- and 25-fold increases of GM1 and GM3 gangliosides, respectively, compared with control emus. The total brain ganglioside sialic acids were, on a wet weight basis, 519 micrograms/g (control A), 658 micrograms/g (control B), and 1800 micrograms/g (affected emu). The familial association seen with this condition suggests that emus are affected by an inherited disorder similar to mammalian gangliosidoses.