Modelling of strategies for genetic control of scrapie in sheep: The importance of population structure.

Scrapie is a transmissible spongiform encephalopathy in sheep and an example of a disease that may be controlled through breeding for disease resistance. Member states of the European Union have introduced strategies for breeding against scrapie based on the selection of genetically resistant breeding rams. An ambitious strategy adopted in The Netherlands consisted of selecting resistant rams for breeding throughout both breeding and production sectors.

Prion Type-Dependent Deposition of PRNP Allelic Products in Heterozygous Sheep.

Unlabelled: Susceptibility or resistance to prion infection in humans and animals depends on single prion protein (PrP) amino acid substitutions in the host, but the agent's modulating role has not been well investigated. Compared to disease incubation times in wild-type homozygous ARQ/ARQ (where each triplet represents the amino acids at codons 136, 154, and 171, respectively) sheep, scrapie susceptibility is reduced to near resistance in ARR/ARR animals while it is strongly enhanced in VRQ/VRQ carriers. Heterozygous ARR/VRQ animals exhibit delayed incubation periods.

Risk-based testing of imported animals: A case study for bovine tuberculosis in The Netherlands.

In intra-EU trade, the health status of animals is warranted by issuing a health certificate after clinical inspection in the exporting country. This certificate cannot provide guarantee of absence of infection, especially not for diseases with a long incubation period and no overt clinical signs such as bovine tuberculosis (bTB). The Netherlands are officially free from bTB since 1999.

Sheep prions with molecular properties intermediate between classical scrapie, BSE and CH1641-scrapie.

Efforts to differentiate bovine spongiform encephalopathy (BSE) from scrapie in prion infected sheep have resulted in effective methods to decide about the absence of BSE. In rare instances uncertainties remain due to assumptions that BSE, classical scrapie and CH1641-a rare scrapie variant-could occur as mixtures. In field samples including those from fallen stock, triplex Western blotting analyses of variations in the molecular properties of the proteinase K resistant part of the disease‑associated form of prion protein (PrP(res)) represents a powerful tool for quick discrimination purposes.

TSE strain differentiation in mice by immunohistochemical PrP(Sc) profiles and triplex Western blot.

Unlabelled: TSE strains are routinely identified by their incubation period and vacuolation profile in the brain after intracerebral inoculation and serial passaging in inbred mouse lines. There are some major drawbacks to this method that are related to the variation in vacuolation that exists in the brains of mice infected with the same TSE strain and to variation between observers and laboratories in scoring vacuolation and determining the final incubation period.

Aim: We investigated the potential of PrP(Sc) immunohistochemistry and triplex Western blotting as possible alternative methods to differentiate between TSE strains.