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Investigation of the Risk of Transmission of Scrapie in Milk of Sheep


<ol><li>To produce milking sheep highly susceptible to scrapie in a flock with a high incidence of scrapie for the supply of milk. Completed 31/10/2009</li>
<li>To rear newborn lambs from a TSE-free flock with milk (or colostrum and milk separately) from infected milking sheep and monitor if infection occurs. Completed 28/02/2013</li>
<li>To rear newborn lambs from a TSE-free flock with milk from infected goats, after establishing that the agent isolated in goats is generally able to infect sheep, and monitor if infection occurs. Completed 01/09/2015</li>
<li>To evaluate the use of PMCA as a method to detect PrPsc in milk from scrapie-affected animals based on the results of the transmission study. Completed 30/09/2010</li>
<li>To provide regular updates to Defra. Completed 31/12/2015.</li></ol>

<p>Objective 2 is dependent on the success of objective 1. </p>

More information

<p>The objective of this study is to investigate whether scrapie can be transmitted within sheep by feeding milk from ewes naturally infected with the scrapie agent to lambs. There is evidence that lambs are infected at a very young age by the oral route and milk as a source of infection cannot be ruled out. Currently available scientific evidence supports the position that TSEs are unlikely to be transmitted through milk but this is mainly based on epidemiological studies in cattle with BSE, which may not be applicable to scrapie, and less sensitive transmission studies into mice because a specific study to investigate transmission in sheep has never been conducted. Milk contains a proportion of cells including lymphocytes and the levels of these cells increase in even mild, sub-clinical mastitis. Such cells have been implicated in blood as the source of TSE infection in blood transfusions. Furthermore, following the detected cases of BSE in goats, there have been concerns that milk products, because they are concentrated, could pose an even greater risk to the food chain. This project aims to maximise chances of transmission via milk by using highly susceptible lambs and dams in mid to late incubation from a highly infected environment. This is a politically important area of research and essential for the most effective policy decisions regarding milk and milk products from sheep and goats. If the infectious agent in milk of ewes affected by scrapie fails to transmit to highly susceptible lambs, it will further support the current scientific opinion that milk and milk products from animals affected by TSEs pose a very low risk of infection.</p>

Veterinary Laboratories Agency, UK
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