Abstract
BackgroundActive surveillance for transmissible spongiform encephalopathies in small ruminants has been an EU regulatory requirement since 2002. A number of European countries have subsequently reported cases of atypical scrapie, similar to previously published cases from Norway, which have pathological and molecular features distinct from classical scrapie. Most cases have occurred singly in flocks, associated with genotypes considered to be more resistant to classical disease. Experimental transmissibility of such isolates has been reported in certain ovinised transgenic mice, but has not previously been reported in the natural host. Information on the transmissibility of this agent is vital to ensuring that disease control measures are effective and proportionate.ResultsThis report presents the successful experimental transmission, in 378 days, of atypical scrapie to a recipient sheep of homologous genotype with preservation of the pathological and molecular characteristics of the donor. This isolate also transmitted to ovinised transgenic mice (Tg338) with a murine phenotype indistinguishable from that of Nor 98.ConclusionThis result strengthens the opinion that these cases result from a distinct strain of scrapie agent, which is potentially transmissible in the natural host under field conditions.
Highlights
Active surveillance for transmissible spongiform encephalopathies in small ruminants has been an EU regulatory requirement since 2002
There is a clear link between susceptibility and sheep genotype [1], and many countries are implementing disease control programmes based on breeding for resistance
In 2002, regulatory requirements for active TSE surveillance were implemented across the EU, and a number of countries have subsequently reported atypical isolates, full details of which can be found in the EFSA opinion of 2005 [7]
Summary
Active surveillance for transmissible spongiform encephalopathies in small ruminants has been an EU regulatory requirement since 2002. Most cases have occurred singly in flocks, associated with genotypes considered to be more resistant to classical disease Experimental transmissibility of such isolates has been reported in certain ovinised transgenic mice, but has not previously been reported in the natural host. In 2002, regulatory requirements for active TSE surveillance were implemented across the EU, and a number of countries have subsequently reported atypical isolates, full details of which can be found in the EFSA opinion of 2005 [7]. It has recently been reported for the first time in the Southern hemisphere, in a sheep native to the Falkland Islands [8]
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