UK's first case of H-type BSE confirmed by DEFRA [Archive]

flatfish

03-19-2007, 04:22 PM

Subject: Re: SEAC ANNUAL REPORT 2006
Date: March 19, 2007 at 9:58 am PST

SPONGIFORM ENCEPHALOPATHY ADVISORY COMMITTEE
Draft minutes of the 96th meeting held on 20th February 2007

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ITEM 5 – CONSIDERATION OF FUTURE DISCUSSION OF
UNUSUAL CASES OF SPONGIFORM ENCEPHALOPATHY IN
CATTLE (SEAC 96/2)
14. The Chair explained that the purpose of this item was to consider
the scope of a future discussion of unusual cases of BSE in cattle.
Such cases had been termed ‘atypical BSE’ by some researchers,
however, as had been agreed at SEAC 93, this was a misleading
term and should be avoided. SEAC was asked to identify relevant
data not highlighted in SEAC paper 96/2, key researchers that
could be invited to present data and contribute to discussions and
questions for the future discussion.
15. A member noted that most unusual BSE cases had been
characterised on the basis of PrPres banding patterns on western
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blot. Cases described as H-type gave a normal distribution of
PrPres glycoforms with a non-g*****ylated band of higher molecular
weight than normally observed. Cases described as L-type gave
an unusual distribution of PrPres glycoforms and a non-g*****ylated
band of lower molecular weight than normally observed. H-type
cases had been identified in France and the Netherlands, L-type
cases in Italy and both types had been found in Germany.
Transmission experiments using bovinised mice had been
conducted and, whilst the L-type was transmitted with a shorter
incubation period compared with BSE, the transmissibility or
incubation period of the H-type was unclear from the information
available. L-type had also been transmitted to macaques with a
shorter incubation period compared with BSE. Transmission
studies with material from H- and L-type cases into cattle by
intracerebral (ic) inoculation are underway but no data are
available at present. Two unusual BSE cases had also been
identified in Japan, one of L-type and the other with a low content
of dig*****ylated PrPres and a non-g*****ylated band of lower than
usual molecular weight. Data on unusual BSE cases reported in
the United States of America (USA) is very limited. In summary,
the information suggested that there appeared to be at least two
strains giving rise to the unusual cases of BSE. The data raised a
number of questions that could be considered at a future
discussion:
• Are all the cases in Europe, USA and Japan of the same two
strains or are there further strains?
• What is the origin of these unusual forms of BSE and how are
they related to BSE?
• Are these unusual cases examples of sporadic or
spontaneous BSE in cattle and if so, how can the same
strains appear in a number of countries?
• Was the BSE epidemic in the UK initiated by intra-species
transmission from such a sporadic BSE case?
• What is the tissue distribution of PrPSc and infectivity in these
animals?
• Are all the cases of unusual BSE transmissible to mice?
• Can these unusual BSE cases be transmitted to humanised
mice?
• Are these unusual BSEs related to cases of sporadic CJD in
humans as there are similarities in glycoform profile?
16. The committee agreed that it would be important to discuss the
available data on unusual BSE cases at the next SEAC meeting.
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17. Members noted that the transmission of Bovine Amyloidotic
Spongiform Encephalopathy to macaques indicated that the clinical
signs differed from signs arising from transmission of BSE. This
was important as it indicated it may be possible to identify and
distinguish infections that occur naturally. It is also important to
understand the tissue distribution of the agent giving rise to
unusual cases of BSE. Dr Matthews noted that transmission
studies had begun in cattle, however interpretation of these data
would be complicated as the ic route of inoculation had been used.
It is not known if studies using the oral route are underway.
Members asked about information available from necropsy of
unusual BSE cases. Dr Matthews explained that detailed post
mortem examinations of the brains of the Italian unusual BSE
cases had been conducted, however most of the other cases were
characterised only by western blot analysis. The two USA cases
had also been characterised by immunohistochemistry (IHC).
18. Members asked if it was known whether a relationship between the
unusual BSE cases and their genotype had been found. Dr
Matthews responded that there was very little information, although
known polymorphisms had been identified in one USA case and
one French case.
19. Members noted that no unusual BSE cases had been found in the
UK and asked whether UK surveillance was sufficient to detect
unusual BSE cases. Dr Matthews explained that UK and French
surveillance was comparable and, although methods used to
detect BSE differed between laboratories, methods used in the UK
should be capable of detecting unusual BSE cases. Projects are
underway to look for evidence of unusual cases of BSE in archived
samples of historic BSE cases. Mr Burke noted that since 2003,
around 570 BSE-positive animals had been screened by VLA
using a discriminatory test with no unusual BSE cases identified. A
member noted the older age of many of the unusual BSE cases
and asked if old cattle would be tested in the UK. Mr Burke
explained that all fallen stock over 24 months of age are tested in
the UK. Mr Burke suggested that the committee might include
consideration of the effect of current BSE controls on unusual BSE
cases entering the food chain in the future discussion of unusual
cases of BSE. Dr Matthews noted that data on cattle surveillance
could be presented by age to highlight the proportion of older
animals tested as part of the future discussion.
20. Members asked whether other animals in the same cohort as
unusual BSE cases had been tested. Dr Matthews responded that
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such studies may not have been conducted and, even if they had
been, the likelihood of finding cohort cases may be very low.
21. The committee agreed that it would be important to hold as much
of the future discussion of unusual BSE cases in open session as
possible, although noting that some researchers may wish to
present data from incomplete studies in a reserved business
session. It was agreed that the following researchers should be
invited to present data and take part in discussions, following
provision of a list of key questions identified by SEAC:
• Dr Mark Hall (National Veterinary Surveillance Laboratory,
USA) and Dr Juergen Richt (National Animal Disease Centre,
USA) to present data on USA cases.
• Dr Thierry Baron (Unite Agents Transmissibles Non
Conventionnels, France) to present data on French cases.
• Dr Cristina Casalone (Centro di Referenza Nazionale per le
Encefalopatie Animali, Italy) and Dr Fabrizio Tagliavini
(Instituto Nazionale Neurologico, Italy) to present data on
Italian cases.
• Dr Anne Buschmann or Dr Martin Groschup (Friedrich-
Loeffler-Institut, Germany) to present data on German cases.
22. In addition, Professor Lasmézas (SEAC member) would be invited
to present her research data and Japanese researchers would be
invited to provide written material on Japanese cases.
23. The Chair explained that a position statement for publication on the
SEAC website would be prepared based on discussions at the next
meeting. Although there is likely to be much that is unknown, it
would be important to consider the possible public health
implications of these cases and identify knowledge gaps.

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ITEM 9 – ANY OTHER BUSINESS

54. The Chair noted that a paper had been provided to update the

committee on an ongoing study on the susceptibility of red deer to

BSE. To date, BSE had transmitted to four ic challenged deer,

however no orally challenged deer had succumbed to the disease.

http://www.seac.gov.uk/minutes/96.pdf

TSS