In New Zealand facial eczema is one of the most important diseases of sheep, with annual losses that have been estimated to be over $120 million in some years1. It occurs seasonally in the summer and autumn in most areas of the North Island and occasionally in northern areas of the South Island.
The disease is caused by a toxin (sporidesmin) which irreversibly damages the liver.
The toxin is produced by a fungus called Pithomyces chartarum.
The fungus builds up in the dead mater of pastures in response to warm and moist conditions and produces spores which contain the toxin. These spores are what is ingested by the animals.
The liver damage caused by the sporidesmin toxin can lead to the following clinical signs:
Swollen drooping ears.
Restlessness, shaking of the head and ears or scratching of affected areas and seeking shade.
Peeling off of the skin, particularly on exposed white areas.
Loss of weight.
For every clinically affected animal there will be many more sub clinically affected.
Sub clinically affected animals generally have reduced fertility and fecundity (ewes) or reduced growth rates (lambs). The affected ewes will often lose condition in late pregnancy and have higher death rates and poor lamb survivability.
Affected sheep should be given shade. One of the most effective methods is to keep affected sheep in the woolshed during the day (with covered windows, water and hay) and let them out to graze at night.
PREVENTION AND CONTROL
Monitor spore counts to identify safe and dangerous paddocks for grazing.
Use crops or supplementary feeds to avoid grazing high spore count pastures.
Sell lambs early before the risk period.
Spray pastures with fungicides to prevent further fungal growth for six weeks.
Dose stock with zinc to prevent or reduce liver damage.
Drench stock with a zinc oxide slurry every week.
Use zinc oxide intra-ruminal boluses (approximate duration six weeks).
Breed for resistance by buying in high facial eczema tolerant rams.
West D.M. Bruere and Ridler A.L. The sheep. Health, disease and production. 2nd edition 2002.
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