Wetenschap - 9 september 2010

Scrapie can be eradicated

Dutch sheep farmers are using a breeding programme to gradually drive out the animal disease scrapie. An extra campaign is needed to eradicate scrapie entirely, concludes the Central Veterinary Institute in the journal BMC Veterinary Research.

The Ministry of Agriculture wants to eradicate scrapie using a special breeding programme with rams that are resistant to the prion disease. There was a statutory obligation to use these rams from 2004 to 2007, as at that time it was not possible to differentiate between scrapie and BSE. Now that distinction is possible and, as scrapie is not a threat to human health, the breeding programme to combat scrapie has been made voluntary.

Properly informed
In 2007, 55 per cent of the adult sheep population was resistant, and that percentage had increased to 62 per cent by June of this year. Marielle Melchior of the Central Veterinary Institute says eighty per cent need to be resistant if scrapie is to be eradicated. She doubts whether that eighty per cent will be reached without additional action and she is advising the Ministry to keep the sheep farmers properly informed.

More time
Only two sheep with scrapie have been found this year in tests at the abattoirs. Eight years ago there were about fifty diseased sheep a year. 'The Ministry and the sheep-farming sector are on the right track but now they need to finish the job', says Melchior. 'Most of the large-scale sheep farmers have implemented the breeding programme properly, but not all the small-scale sheep breeders have replaced their scrapie-susceptible rams with resistant rams. It will require more time before they too have scrapie-resistant sheep for breeding. You don't want scrapie still persisting in a few susceptible sheep on these farms.'
Prion disease
Scrapie is a prion disease, like BSE. Prions are proteins that are misfolded. Because of this, the body cannot break them down so well and they accumulate in the brain. That leads to scrapie in sheep, to mad cow disease in cows and to Creutzfeldt-Jakob disease in humans. Unlike the other two, scrapie has been known for more than a hundred years and breeding for resistance has been possible since the 1990s.

Re:ageer