Experimental induction of ovine polioencephalomalacia

Polioencephalomalacia (PEM) was induced in sheep, with an overall incidence of 63 per cent, using local bracken fern (Pteridium esculentum) rhizomes as a source of thiaminase type 1 and pyridine as a basic cosubstrate. The condition was thiamin responsive and PEM was confirmed by histopathological examination. In a separate experiment to examine the effect of pyridine, it was shown that, for the duration of the experiment, pyridine had no toxic effect and caused no histologically detectable brain lesions.