Ovine scrapie: Priorities and importance

Ovine and caprine scrapie occupies a unique place among animal transmissive spongiform encephalopathies (TSE). It is an object of intensive biomedicin al, ecological and economical studies. Its causative agents are demonstrabl y associated with the development of TSE in farmed minks, goats and moufflo ns. Ovine strains of scrapie occurring in North America (particularly in th e USA) differ from strains which occur in Europe and were present at the on set of development of TSE in three species of deer living in free nature an d in captivity in the USA. The studies dealing with the development of bovi ne spongiform encephalopathy (BSE) of the English type have indicated justi fiably that its origin is associated with one (or more) heretofore unidenti fied ovine strain. The development of a variant form, the Creutzfeldt-Jacob disease in humans, and transmission of the BSE agent to several families o f bovidae, felidae and primates, puts stress on its zoonotic potential. All this leads to the conclusion that domesticated sheep are the decisive rese rvoir species of animal TSE. They have been infected to an unknown extent w ith the causative agent of BSE probably through contaminated meat-bone meal . The occurrence of natural ovine prion isolates with properties similar to those of the BSE agent requires that scrapie should be included in the sur veillance of human and animal TSE. At present, scrapie is a noticeable dise ase also in other than European Communities Member States. It is on the lis t B of the International Epizootics Office. Many countries have initiated c ontrol of ovine scrapie. It should therefore become a topical question also in Central and Eastern European countries. Elimination or even eradication of ovine scrapie (or its causative agents) from populations of small and l arge domestic ruminants is the prerequisite for prevention of penetration o f ovine pathogenic prions into the human feed chain. Moreover, it should be ensured that these species will be able to produce foods of a new type (im munotrition and similar) or proteins with therapeutic effects in the near f uture. Our study established that the PrP genotype of Valachian rams, the S lovak autochthonous breed, contains also VRQ and ARQ alleles encoding the s usceptibility to scrapie. Their selection is part of the improvement of Slo vak Valachian sheep towards resistance to scrapie.