Neuroaxonal dystrophy in Merino-Border Leicester × Polled Dorset lambs.

Case Report: The clinicopathological features of neuroaxonal dystrophy (NAD) in 2 lambs are described. Of 40 Merino-Border Leicester × Polled Dorset lambs on a property in north-eastern Victoria, 4 presented with marked ataxia and listlessness, and 2 affected animals (2 days and 2 weeks of age, respectively) of both sexes were necropsied. Numerous axonal swellings (spheroids) were found in the central nervous system, particularly in brainstem nuclei and spinal cord grey matter, and there was severe spinal cord demyelination.

Conclusions: This is the first report of NAD in such crossbred lambs; the affected animals were much younger than in previously described cases of ovine NAD and myelin loss was of much greater magnitude than previously reported.