Agriculture Victoria Senior Veterinary Officer Robert Suter said serious outbreaks of PRGT occur in high rainfall areas across Victoria when big springs were followed by a hot and dry autumn.

PRGT can occur when fungal endophytes in old or naturalised perennial ryegrass pastures produce high levels of alkaloids that can be toxic to livestock.   

Mr Suter said an estimated 90,000 sheep and 500 cattle died from direct causes of these alkaloids and a similar number from indirect causes in 2002. 

PRGT symptoms include nervous disorders such as staggers, ill thrift, heat stress, scours and possibly lower fertility.