Lolium species

Abstract

DISTRIBUTION: Agriculturally cultivated, also growing in disturbed places.

BOTANICAL DESCRIPTION: General: An annual, dense, tufted, soft grass. Leaves: The leaves are green and shiny and the culms usually unbranched. Flowers: The inflorescence is flat with the spikelets evenly arranged on either side of the central axis. The size of the awns is up to 10 mm, which distinguishes it from Lolium perenne.

TOXIC PRINCIPLE: The seedheads can contain nematode galls (Anguina sp.) but when they are overgrown by the bacterium, Rathayibacter toxicus, bacterial galls containing the neurotoxic orynetoxin are produced.

SYNDROMES: ARGT - Annual Rye Grass Toxicosis ABPE – Acute Pulmonary Oedema and Emphysema.

SYSTEMS AFFECTED: Central nervous and respiratory systems.

CLINICAL SIGNS: Clinical signs precipitated by disturbing or exercising - especially in mild cases. Chase animals for 100-200 metres if suspected. • Hypersensitivity• Muscular twitching• Locomotory disturbances - unsteady, saw horse gait or high-stepping gait • Clonic/tonic convulsions (1-3 minutes). Lateral recumbent. Opisthotonus - legs extended • Permanent recumbent with leg paddling, twitching, trembling and show nystagmus Death 4 - 12 hours after onset.

NECROPSY: Macroscopical findings: • Rapid rigor mortis • Lung oedema • Subepi- and endocardial haemorrhages • Hepatosis.

HISTOPATHOLOGY: • Not much. • CNS changes consistent with anoxia arising from vascular obstruction.

TREATMENT: •Tranquillizers and sedatives eg. Diazepam / xylazine • MgSO4 injections (every 6-8 hours for 3 days) 200mg/kg/ i/m.

CONTROL: • Inspect stock on ryegrass pastures every day or even twice/day. Outbreak: Remove animals immediately • Identify infestation: Representative seed specimens collected from camps and forward to Stellenbosch for final identification. Identify the eelworm and bacterial galls with the aid of a stereomicroscope. If infested: • Grow wheat, rye or barley and spray with herbicide to kill rye grass. • Graze heavily before seed heads mature • High mowing of pasture • Burn toxic pasture.