The disease causes them to shake and stagger in an in-coordinated way, and so accidents such as falling off bluffs, drowning and entanglement in fences are real risks for affected animals in some paddocks. Mr Burnell urges farmers to be on the lookout for early signs. This is most obvious when stock are agitated or alarmed, for example by sudden noise or movement. Sheep, cattle and horses can be affected, and wapiti deer and alpacas are particularly susceptible. The cause of ryegrass staggers is a toxin produced by a fungus or endophyte which grows in some types of perennial ryegrass, particularly in the leaf sheath and older leaves, in late summer and autumn.
Stock are at risk if forced to graze into dead litter close to the soil.
The toxin can damage part of the brain of animals which graze the pasture. Fortunately the damage is usually reversible if affected animals are moved to safer grazing. At present there is no way of preventing the fungus from growing or of treating animals on affected pasture. However there are strains of ryegrass which are not likely to support the fungus, and in the long-term using these in pasture may be an effective preventative. Mr Burnell says that at the first signs of ryegrass staggers, it is best to consult a veterinarian for advice, as there are other diseases that may cause similar signs.