21 April 1995

Guidelines to fight parasite

SHEEP scab outbreaks have increased ten-fold since compulsory dipping was phased out.

Thats the view of Dr Karl Linklater, director of veterinary services at the Scottish Agri-cultural College, who feels it is up to farmers to keep control of scab.

"There is a wide range of chemicals available, so we are not short of tools to fight the parasite," he says.

His view is supported by John Thorley, chairman of the National Sheep Association (NSA). "Observe the rules: treat and isolate. Anyone with scabby sheep must not take them to market. The problem has to be tackled in a very fundamental way." He is most concerned for stock grazing common land. "It is there producers have the biggest difficulty controlling scab," he says. "It is getting beyond a joke."

Economically scab is the most important disease in sheep. A third of weight gain is lost to the disease and a third of those sheep infected die when left untreated. The mite, Psoroptes ovis, which causes scab is spread from sheep to sheep in 72% of cases. Sheep bought through dealers are three times more likely to carry the mite than farms without the disease. Implements and transportation are the other infectious medium.

To help combat scab it is advised producers:

&#8226 Isolate and treat bought-in sheep and those returning from market.

&#8226 Contain the flock.

&#8226 Ensure correct use of ecto-paraciticides.

&#8226 Take care with transporters.

&#8226 Report all suspects.

Dr Linklater urges producers using Ivermectin to treat scab not to return stock to the same pasture or buildings for 15 days after the second injection – which should be seven days apart from the first one. &#42