What is it?

  • A neurological disease of sheep, cattle, horses and ponies, deer and alpacas.
  • Alpacas appear to be particularly susceptible.

When and where does it occur?

  • It occurs commonly throughout the North Island and as far south as North Otago.
  • It is most common in summer and autumn.

What is the cause?

The disease is caused by the ingestion of a toxin produced by a fungus (or endophyte) in perennial ryegrass. The highest concentrations of toxin are in the leaf sheath and seed head.

The toxin has a specific damaging effect on the cells in the cerebellum of the brain that coordinate movement.

What are the signs?

  • The signs are most obvious when affected animals are disturbed and forced to move.
  • Affected animals become anxious about being approached.
  • In mild cases, there is slight trembling of the head and of the skin of the neck, shoulder, and flank.
  • More severe cases show head nodding and jerky movements, swaying while standing, and staggering during movement.
  • In the most severe cases, they have a stiff-legged gait, short prancing steps, and may collapse with rigid spasms that last for up to several minutes.

What happens to affected animals?

  • The disease itself is not fatal, but there is a real risk of injury or death as a result of accidents.
  • Affected animals lose weight as they don’t graze as much.
  • They may not be able to drink sufficient water.
  • They can become caught up in obstacles like electric fences.
  • They can fall into holes and ditches and over bluffs.
  • They can drown in creeks, dams, drains, and swamps.
  • Affected dairy cows produce less milk and become distressed when herded. Severely affected cows may fall over in the bail.
  • Horses and ponies become more difficult to handle, and even dangerous to ride.

What can you do?

  • Remove stock from hazardous pasture if you can.
  • If safe pasture is not available, put the stock into yards and feed them hay (or silage/balage) and plenty of clean water.
  • Handle affected stock quietly.
  • Don’t disturb affected animals unnecessarily.
  • The best long-term solution in areas where the disease is a problem is to replace the affected ryegrass pasture with endophyte-resistant grasses.
  • If you have problems with ryegrass staggers, contact your veterinarian.

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