National effort required to rid sheep of scrapie
By James Garner
RIDDING the national sheep flock of scrapie is a long-term objective but current eradicating tools require a national effort from the countrys sheep producers.
Last weeks announcement by the governments BSE advisory committee, SEAC, as reported in farmers weekly (News, April 16), means that after consultation with industry MAFF will announce a disease control programme to eradicate scrapie.
But industry leaders are divided as to whether sheep producers are currently doing enough to reduce the diseases incidence.
NSA chief executive John Thorley says that there is much work already being done with blood genotyping and more draconian rules might be counter-productive.
"Where this has happened in other countries they have failed to eradicate it. We should continue going down the current route which is bound to reduce the disease below what are already low levels."
Mr Thorley says that sheep breeders are doing as much as they can. "To do any more might lead to negative results as breeders can only select for a small number of traits."
While head of NFU livestock Steve Rossides, says that more can be done. "The SEAC announcement is a salutary reminder that scrapie is an important issue."
But Mr Rossides warns how dangerously things can be in spun the media, especially emotive issues like scrapie. "We have learned from BSE not to sweep things under the carpet."
Currently, genotyping is the only way breeders can reduce the incidence of scrapie. BSE consultant Ray Bradley says theres no rapid solution to eradicating it.
"We need to take a longer term view. Let the research develop so we can test for the disease and then eradicate it by getting rid of infected animals."
But time is on the side of research as there are measures in place to protect public health because specified offals, spleen and brain are removed from the food chain.
"It might take 20 years or more to eradicate scrapie. But a live test that works might be discovered tomorrow, could be validated in a year and therefore the time to eradicate the disease can be reduced."
Matthew Baylis, senior resear-cher at the Institute of Animal Health, Compton – currently leading a project on the disease – says: "If you want to be rid of scrapie, blood genotyping for susceptibility must be done by every producer and not just pedigree breeders."
The IAHs scrapie research projects initial findings suggest that for commercial flocks selling slaughter lambs, breeding scrapie resistant sheep it is not as important. This is because theyre selling lambs at a young age before they develop the disease.
However, in crossing flocks which are breeding replacement ewes for sale, genotyping is important as these ewes could be carrying and sustaining the disease, says Mr Baylis.
He says that flocks with and without scrapie have high proportions of animals with susceptible genotypes and sheep breeders with flocks who do not have scrapie should consider genotyping.
"We havent found a farm yet that could not have scrapie. It is surprising that it is not more common and we are still not sure why one farm has it and another doesnt."
However, initial indications suggest that besides maternal transmission, the environment has a part to play in transferring scrapie.
"We know that lambing practices can lead to disease transfer and that better lambing hygiene could lower the risk of transfer."
Environmental areas of concern are that scrapie is being carried by hay mites in feed, surviving in certain soil types or being passed on by rams during mating. *
• Eradicate scrapie.
• Scrapie genotyping.
• Live test to be developed.