[Jacob-list] Fwd: PRO/AH> Scrapie, atypical, sheep - UK (02)

[Katherine Wisor]

Thought this might be of interest  to the LIST!  Happy Easter from 
Creeks End Farm!   >Katherine

Begin forwarded message:

> From: ProMED-mail <promed at promed.isid.harvard.edu>
> Date: April 9, 2004 12:12:16 PM EDT
> To: promed-ahead at promedmail.org
> Subject: PRO/AH> Scrapie, atypical, sheep - UK (02)
> Reply-To: promed at promed.isid.harvard.edu
>
>
> SCRAPIE, ATYPICAL, SHEEP - UK (02)
> **********************************
> A ProMED-mail post
> <http://www.promedmail.org>
> ProMED-mail is a program of the
> International Society for Infectious Diseases
> <http://www.isid.org>
>
> Date: Fri, 9 Apr 2004
> From: ProMED-mail <promed at promedmail.org>
> Source: NewScientist.com news service, 8 Apr 2004 [edited]
> <http://www.newscientist.com/news/news.jsp?id=ns99994869>
>
>
> Mysterious BSE-like disease found in sheep
> ------------------------------------------
> A massive research programme to find out whether BSE is circulating in
> British sheep has turned up its first suspicious result. But while
> scientists say the sheep did not have conventional BSE, they cannot 
> rule
> out the possibility that it could have had a new form of BSE (mad cow
> disease) that has adapted to sheep.
>
> Britain's Department for Environment, Food and Rural Affairs [DEFRA] 
> has
> announced that the Veterinary Laboratories Agency (VLA) in Weybridge,
> England, had found "a type of scrapie not previously seen in the UK".
> Scrapie is a sheep disease similar to BSE which is not generally 
> thought to
> harm people.
>
> The Department for the Environment, Food and Rural Affairs (DEFRA) 
> said the
> disease-causing prion detected in the sheep's brain "had some
> characteristics similar to experimental BSE in sheep", but that on 
> other
> tests it resembled neither BSE nor "previously recognised types of
> scrapie". The UK's Food Standards Agency said in a statement:
> "Uncertainties still remain on this issue. However, based on the best
> scientific evidence to date, we are not advising against eating lamb 
> and
> sheep meat."
>
> There have long been fears that sheep which ate cattle-derived meat and
> bone meal during Britain's BSE epidemic in the 1980s might have 
> acquired
> BSE, although they have never been confirmed. Unlike BSE in cattle, 
> prion
> diseases spread directly from sheep to sheep. So any BSE in sheep could
> still be circulating despite subsequent bans on animal-derived feed.
> Furthermore, sheep experimentally fed BSE develop a disease
> indistinguishable from ordinary scrapie, making detection very 
> difficult.
> Yet the prion from such animals still behaves like BSE, and could 
> cause the
> fatal human disease vCJD. Worse, sheep carry prions in more tissues 
> than
> cattle, including the muscle that people eat, so BSE-infected sheep 
> could
> cause more human disease than mad cows.
>
> A previous attempt to determine whether British sheep had acquired BSE 
> went
> spectacularly wrong in 2001 when sheep and cattle brains were mixed up 
> in
> the lab. But since then, the VLA has tested the brains of all 1019 
> newly
> reported cases of scrapie, as well as 1125 scrapie brains dating back 
> to
> 1998, with tests designed to distinguish scrapie from BSE.
>
> The new result announced on Wednesday, from a sheep recently reported 
> with
> scrapie symptoms, is the first to give results that resembled BSE. 
> Danny
> Matthews of the VLA told New Scientist that in a prion test called a
> western blot, the sheep's brain did not bind an antibody called P4. P4 
> also
> does not bind prions from sheep experimentally infected with BSE, but 
> does
> bind all but one forms of scrapie tested with it.
>
> Also like BSE, the form of the prion without a sugar attached to it 
> had a
> lower molecular weight than the form found in scrapie. But the ratio of
> prions with different numbers of sugars on them looked like scrapie, 
> not
> BSE, says Matthews. Most conclusively, immunohistochemistry (IHC), in 
> which
> thin slices of the sheep's brain were stained with various antibodies,
> showed prions had accumulated in different parts of the brain and 
> different
> kinds of cells from BSE -- or any known form of scrapie.
>
> The IHC pattern reliably indicates BSE, says Matthews, having been 
> constant
> in the 100 experimentally infected sheep of different genetic varieties
> tested so far. But so little scrapie has been tested, he says, it is 
> not
> known if one strain might give these results on the tests. One 
> possibility,
> he says, is that the sheep might have been carrying a prion initially
> derived from BSE. Passage into new species is well known to change 
> prions.
>
> BSE from experimentally infected sheep has so far been passed to just 
> one
> more round of sheep, with no apparent change. "But we don't know if 
> passage
> through many sheep, of different genetic types, might change it so it 
> no
> longer gives the same pattern in IHC or western blots," says Matthews.
> "Those experiments are underway now."
>
> Any such new incarnation of BSE in sheep may -- or may not -- have 
> lost its
> ability to harm humans.
>
> [byline: Debora MacKenzie]
>
> -- 
> ProMED-mail
> <promed at promedmail.org>
>
> [As rightly commented, the main current worry, related to a possible
> presence of BSE in sheep, is its infection routes. Cattle are thought 
> to be
> infected with BSE mainly, if not only, orally -- namely by the 
> consumption
> of infected meat & bone meals (MBMs). The banning of this commodity is
> regarded to terminate the infection cycle.
>
> Scrapie spreads among sheep laterally (from one animal to another via
> direct or indirect contact) and maternally (from a dam to its 
> offspring,
> either vertically or laterally by close post-parturient association). 
> Thus
> -- provided BSE, if infecting sheep, behaves like the scrapie agent -- 
> the 
> discontinuation of feeding sheep with MBMs will not terminate the 
> infection
> cycle. - Mod.AS]
>
> [see also:
> Scrapie, atypical, sheep - UK              20040408.0952
> Scrapie, atypical, sheep - France: OIE     20040201.0390
> 2003
> ---
> Scrapie - Norway: new phenotype            20031117.2857
> 2002
> ---
> BSE, potential for emergence in sheep - UK 20021119.5847
> BSE? Sheep - USA (Vermont)                 20020412.3937
> BSE, potential for emergence in sheep      20020106.3180]
>
> ..................arn/pg/sh
>
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