It has been know for over 100 years that sheep, cattle and horses can develop a 'staggers' syndrome after ingesting the seed heads of paspalum (Paspalum dilatatum) infested with the fungus Claviceps paspali. Cattle are most commonly affected, mainly because they predominate in the coastal areas of NSW, Victoria and south western Western Australia where paspalum thrives (AJ Cawdell-Smith et al 2010, Finnie et al 2011). The toxin causes degeneration in some brainstem nuclei and the spinal cord (Finnie et al 2011). However, affected animals usually recover uneventfully if they survive misadventure.
Eighty two Angus steers purchased in mid-April 2011, were moved into a paspalum dominant paddock in the Blayney district on the central tablelands of NSW. The paddock had been spelled for 3-4 months and the paspalum was in head. The owner, after a ten-day absence returned in early May 2011 to find two steers unable to stand (Figure 1). He described them as 'scrabbling around on all fours.'
On inspection, the two recumbent steers were alert, reactive and aggressive when approached. When attempting to rise from sternal recumbency, they paddled in an uncoordinated fashion and were unable to gain their feet to stand. They also had muscle tremors.
Several steers in the mob also developed hypermetria and a swaying gait as they were moved under some pressure.
The mob was diagnosed as suffering from paspalum staggers because ergot-affected paspalum (Figure 2) dominated the paddock, the clinical findings in the two recumbent steers was consistent with the disease and also because when the mob was pressed others developed clinical signs.
The mob, apart for the two recumbent steers was moved into a paddock with less paspalum. They recovered uneventfully although forced exercise induced signs of incoordination for 2-3 days after removal. The two recumbent steers were sedated then moved from the affected paddock. One steer recovered after 5 days. The remaining steer was fed and watered for 21 days before regaining its feet.
In our experience, paspalum staggers is rare on the tablelands of NSW. This is because paspalum dominant pastures are uncommon. The exceptionally high rainfall over the summer and autumn of 2010-11, conducive to abundant rank growth of paspalum and the development of Claviceps infestation, is also unusual.
The differential diagnosis of 'falling with tremors syndromes' includes phalaris staggers, perennial ryegrass staggers and the mycotoxicosis due to the ingestion of wheat and barley sprouts infected by Aspergillus clavatus (Bourke 2008, Finnie et al 2011).