The Phenotype of Atypical Scrapie in Cattle

<p>Current European Union (EU) legislation requires member states to monitor cattle for the presence of bovine spongiform encephalopathy (BSE), which is carried out by testing the brains of slaughtered cattle and suspected clinical cases. These requirements are subject to modifications given the decline of BSE cases within Europe and the high costs of testing cattle, which was outlined in the Transmissible Spongiform Encephalopathy (TSE) Roadmap 2, published by the European Commission and endorsed in general by Defra. However, it was emphasised that the ability to detect new forms of TSEs in cattle must be maintained, which requires investigation of the full spectrum of TSEs that may occur in cattle.</p>
<p>Studies in cattle experimentally infected with naturally occurring TSE agents have been used to determine the disease forms and to investigate whether the current tests were able to diagnose and distinguish them from classical BSE, the disease responsible for the UK epidemic. These disease forms were diagnosed successfully by these tests. Another naturally occurring TSE has been recently found in UK sheep and named “atypical scrapie” to distinguish it from the classical form known in the UK for centuries. Atypical scrapie has been found retrospectively in sheep killed around the same time as the first cases of BSE were reported in the UK and is likely to have occurred even earlier. It is not known whether atypical scrapie can transmit to cattle, how the disease looks like and whether it can be diagnosed by the tests applied to brain samples. As body parts of sheep scrapie cases almost definitely have been processed to meat and bone meal (MBM), which is believed to be the source of the BSE epidemic in the UK by feeding it to cattle, cattle are likely to have ingested MBM contaminated with the atypical scrapie agent. The proposed study aims to determine whether atypical scrapie from sheep can transmit to cattle and to characterise the resulting disease. This will be achieved by inoculating five cattle with a brain from a clinically affected atypical scrapie sheep by the intracerebral route, which is known to be the most effective route to produce disease. Five control cattle will be similarly inoculated with saline solution. Cattle will be culled upon development of clinical disease, which together with the findings from the diagnostic tests, will enable us to describe the disease in full detail and compare it with BSE. Control animals culled at the same time as diseased animals will enable comparison with changes occurring due to age or the environment.</p>
<p>The brain of the sheep used for inoculation has been inoculated into mice to determine the biological characteristics of this particular TSE agent (funded by other projects); we will similarly inoculate two groups of ten mice with brain material from the first clinically affected animal to assess whether the biological properties have changed after transmission to cattle.</p>
<p>Overall, this project will further our understanding of the range of BSE forms that may be present in the cattle population.</p>