23 June 1995

Non-OP answer to scab control

By Jeremy Hunt

SUCCESSFUL trials on a Cumbria sheep farm mean the first non-OP dip effective against scab and blowfly strike will be on the market this season.

Bearing the trade name Robust, and available through Youngs, the synthetic pyrethroid high-cis cypermethrin dip is twice the price of OP products. But its non-OP status and added cover against blowfly is expected to give it a marketing edge.

Ken Prestons 400-ewe flock at Keld Head Farm, Askham, Penrith, was used by ministry vets to test the dips efficacy against scab before being awarded its official MAFF licence.

Sheep scab turned up in Mr Prestons flock for the first time last spring after he bought 24 in-lamb Mule ewes from an auction mart. But, like many others who have never seen the disease in its early stages, initially he began treating for lice using a pour-on.

"The lambs more than the ewes started rubbing themselves but after two pour-on treatments for lice there was no improvement," says Mr Preston. Looking back he recalls speaking to many other farmers at the time who were also having supposed problems with lice infestations.

"Like me I think a lot of them had not had any previous experience of scab and just presumed lice were causing the problems. We have all seen dramatic photographs of the very sick ewe suffering from scab but mid-summer outbreaks are not as obvious even though the symptoms worsen as the season progresses."

By mid-July the entire flock, including the bought-in ewes, had been sheared and both ewes and lambs were again treated for lice. Scab was not spotted, though some skins appeared to have scurvy. The removal of the fleece can cause the disease to be temporarily checked, though it in no way acts as a cure.

"The ewes did well after clipping but by early August the lambs were still itching," says Mr Preston. "I still had no reason whatsoever to suspect scab."

But when the vet was called in sheep scab was confirmed. Recent years have seen the flock treated with a mid-season pour-on blow-fly treatment and a September dipping undertaken by a contractor.

The thick fleeces of the lambs and the onset of cooler, moist weather favoured a serious spread of the mite. The lambs were dipped immediately but Mr Preston also agreed to take part in the official ministry test of the Robust non-OP dip.

Within a week the entire flock was dipped meticulously in an operation entirely undertaken by MAFF staff from the Central Veterinary Laboratory, Surrey.

"The ministry staff did the whole job," says Mr Preston. "All I had to do was run the sheep into the dip and even though I was standing very close there was very little smell. It certainly didnt smell like sheep dip."

Only 35 ewes were actually confirmed as suffering from scab. Individual scabby ewes were dipped at intervals with the rest of the flock to check chemical persistency. That was in mid-September. The MAFF team returned two months later and the 35 affected ewes were checked thoroughly.

"When the dip has worked the scab should lift off with the wool as the fleece grows," says Mr Preston. "That is exactly what had happened with the 35 ewes. We were 100% clear of sheep scab."

A final ministry check in November confirmed the total absence of the disease.

"The lambs, which were dipped with Robust just before the official test, went on to do tremendously well," he says.

This year the flock will be treated with a pour-on blow-fly treatment in mid-summer and will be dipped using Robust in September.

"Scab can be very hard to detect but there is one thing that can be a useful pointer – wool on wire. Our fences were covered with wool. We thought it was lice but now we know better."

Recommended for use as a double dip, two weeks apart to control scab. Sold to farmers as Robust, Crovect or C-Vet. &#42