[Maedi and maedi control (author's transl)].

Maedi/visna is a chronic progressive interstitial pneumonia of sheep caused by a persistent infection with a retrovirus. Approximately thirty per cent of the sheep population in the Netherlands carries antibodies to maedi virus. An experimental eradication scheme based upon serological testing with ELISA and culling of reactors every six months was started, recently. Initially, 353 (25.4 per cent) reactors were identified among 1391 sheep in sixteen flocks, whereas the second test, six months later, showed 130/1111(11.7 per cent) reactors. On 11 other farms with high infection level 382 lambs were separated from their dams immediately after birth, ovine colostrum deprived and artificially reared. The lambs were serotested at 6 months of age and 2/382 (0.5 per cent) were found positive, while naturally reared lambs on the same farms scored 39 per cent positive.