Toxicity of Wimmera ryegrass to cattle and sheep in WA and SA is associated with a plant toxin of the tunicaminyluracil antibiotic complex produced in galls in the rye grass seed head by parasitic bacteria (Clavibacter formerly Corynebacterium rathayi) transported by invading plant nematodes (Anguina agrostis).

This disease has not yet been recorded in NSW, but a similar disease involving the same toxin and Clavibacter bacterium has been seen in cattle and some sheep in late 1990 along the Darling flood plains, originating from infected "blowaway grass" (Agrostis avenacea). Clinical signs of ART include neurological disturbances characterised by ataxia and collapse with tetanic and clonic convulsions, ending in death, and abortions in ewes.

Diagnosis

History, clinical findings, gross pathology, histopathology. Evidence of yellow bacterial galls on annual ryegrass plant heads/seeds; identification of Clavibacter sp in feed. Elimination of other diseases associated with neurological signs and CNS oedema (e.g. enterotoxaemia).

Specimens required

1. Fixed liver and brain in buffered formalin
2. Suspect grass or grass seed (e.g. showing bacterial galls).