Morphological changes in the central nervous system of sheep affected with experimental annual ryegrass ( Lolium rigidum) toxicity

Abstract

Material from parasitized annual ryegrass ( Lolium rigidum) (PRG) was dosed to sheep to study changes in the central nervous system in animals affected with annual ryegrass toxicity (ARGT), the often fatal neurological and hepatotoxic syndrome associated with the ingestion of ryegrass parasitized by an Anguina sp.— Corynebacterium sp. complex. In perfusion-fixed brains there was invariably perivascular oedema, particularly in the cerebellar meninges. This oedema was apparently associated with increased vesicular transport of horse radish peroxidase (HRP) by vascular endothelium. Swelling of astrocytic processes occurred, and in animals which survived longer there were diffuse and focal degenerative changes in the neuropil. Ultrastructural study confirmed the presence of distorted capillaries and others occluded by microthrombi. It is concluded that the vascular leakage might be associated with hypertension secondary to the proposed vasospastic effect of PRG, which would also cause ischaemia and the diffuse and focal degenerative changes in the neuropil.