Scab and lice: Flockmasters should act now

14 August 1998




Scab and lice: Flockmasters should act now

By Emma Penny

WITH breeding sales in full swing, sheep producers are urged to take precautions to reduce the risk of introducing scab and lice into flocks, and to identify parasites before treatment.

That advice follows results of an SAC survey released this week, showing that one in six producers had seen scab in their flocks.

Alistair Greig, deputy head of SACs vet division, says the only way to avoid introducing scab with newly purchased sheep is to treat them before they join the flock.

"Even where sheep have been dipped before sale, are you sure it was done properly? They may still be infected if theyve been put though the dipper too quickly or one has been missed where injectables were used," he warns.

Product selection is also highlighted in the survey. Of those asked, one-quarter thought that pour-ons and sprays controlled scab. This is not the case, says Mr Greig. "The only products licensed to treat and control scab are plunge dips and three injectables – ivermectin, doramectin and newly launched moxidectin.

"Newly-purchased sheep dipped in a scab-approved product can join the flock after treatment. But where injectables are used, they must remain in isolation for a fortnight where ivermectin or doramectin are used, and 12 days where moxidectin is injected."

When an outbreak of scab is suspected, vets at SAC and MAFFs central vet lab advise confirming the diagnosis. While scab-affected sheep will rub themselves and lose wool, infestation with chewing lice – an increasing concern throughout the country – exhibits the same symptoms.

Not all products controlling scab will treat lice, so identifying the parasite before treatment vital, says Peter Bates, head of entomology at CVL.

All plunge dipping products control both scab and lice. But where other products are used its important to select those which will treat the parasite concerned. This will also minimise risk of resistance as non-dip products must be safeguarded for future parasite control, he says.

When dipping newly purchased sheep is not a favoured option, it is possible to use a pour-on followed by an injectable. "Use a pour-on first because it has a short withdrawal period, and ensure the sheep remain in isolation. Two to three days later use the injectable. This will control parasites, while the injectable will also kill resistant worms," explains Mr Bates.

"Before using any product, read the label. Follow manufacturers instructions to the letter to ensure effective control," he urges.

PROTECTING FLOCKS

&#8226 Treat all new purchases.

&#8226 Diagnose parasite responsible.

&#8226 Follow makers instructions.


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