Carrier sheep continue to generate debate (if not virus). Michaela obtained
this information from a past colleague:
Sheep are carriers for a relatuively short period of time (up to 3
months). After that they should be "clean" of disease. There is
currently a huge debate on the importance of carriers. Even with
cattle, which become carriers for up to 3 years, transmission from
carrier to susceptible animal is a VERY rare occurrance.
As with all these issues there is no easy solution, because concerned
vets may argue that some sheep may be carriers for a longer period of
time, and if transmission occurs in one instance, that may lead to
Hope that helps,
Wilna Vosloo PhD
Onderstepoort Veterinary Institute
Exotic Diseases Division
And she also sent this comment:
Ask Andrew what the level of TCID is, that a 'carrier' animal excretes in
Re Fred Brown's million fig. it was simply to give lay people an indication
of the level of risk, i.e. verrrry low. Jon Dobson was speaking to
Pirbright today re the risk of carriers and it was stated that risk was
risk. In other words where risk exists,and where does it not, the whole
animal population is 'at risk', therefore slaughter.
Andrew (veterinary scientist) sent this message:
> Our comment: There is a lot to take on board here, but the main points
>that at least some tests for live virus are being carried out on the Brecon
>Beacon sheep, and that statistically such a large percentage of antibody
>positive animals is, quote, "certain" to indicate active disease within
>flock. We still have more questions though . . . . . watch this space.
I very much enjoy the correspondence between yourselves and Andrew King.
I wonder if you are willing to share his email address as there are several
specific questions I'd like to raise with him.
A key issue is whether or not persistently infected - aka carrier - animals
present a risk of infecting other animals or not. There was conference in
the Netherlands not many weeks ago on the topic of carrier animals an FMD -
did anyone from Pirbright attend? - I believe Alex Donaldson was scheduled
to speak there.
Fred Brown and Simon Barteling seem absolutely certain that persistently
infected - carrier - animals present NO risk of infecting other animals,
and that repeated experiments that sought to infect animals from carriers
all failed. Furthermore Gareth Davies told me in a private conversation
that the scientific consensus is now that they - carriers - do NOT present
a risk of infecting other animals.
Yet Andrew King seems to believe that they do.
Now - I may be being simple-minded here - but it seems to me that both
'sides' cannot be right.
The 'answer' may lie in the difference between 'lab people' - Pirbright -
and 'field-oreinted people/epidemilogists' - the others mentioned.
What I mean is it may be possible in a lab to get very small amounts of
live virus from a persistently infected animal if one tries very hard
(scraping throats etc) but equally it may well be true that there is never
enough live virus excreted by a carrier to ever naturally infect another
animal in the real world.
Sadly, I'm told that there are very very few - if indeed there are any -
people at Pirbright who have any real training or experience in
Plainly in the real world one seeks to control the *spread* of the virus
and to reach a point where *clinical disease* no longer occurs. One cannot
hope to actually be certain of eradicating the VIRUS unless one kills every
susceptible animal in the country - because persistent infections are
common - apparently up to 50% of infected sheep become persistently
infected (ie. carriers) for some months post acute infection and no control
policy based on report/detection of clinical disease and slaughter of
affected flocks/herds will work - to eradicate VIRUS or even to eliminate
spread? - when this FMDV serotype often produces undetected disease in
I do not believe that DEFRA's interpretation of ELISA test results with
respect to (WRT) current active infection has any validity.
But IF DEFRA believes it is necessary to kill any epidemiological group of
animals that has seropositive animals - presumably to satisfy trading
partners that UK is FMD-free - then their abuse of science is probably
'irrelevant' at least from their standpoint. I just wish they'd be honest
about what they are doing and why rather than hide behind pseudo-science.
There current ELISA testing approach in the Brecon flocks just does NOT
tell 'em what they claim it does WRT current active infection status.
What's not clear to me is whether they (DEFRA) understand that and are
simply lying, or (worse in my opinion) they really do believe that this
test approach can tell 'em something about current active infection status
in which case they are deluded in my opinion.
What I'd like to know is how much the Pirbright folk - or any other FMD
experts - were consulted, if at all, when DEFRA drew up this plan to test
the Brecon hill flocks. Do we have another instance of DEFRA failing to
seek relevant and appropriate expert advice when devising policy?
The Brecon 'case' would seem to have been an ideal opportunity to field
test/validate the PCR-based rapid test machine - remember that? - which I
understand is at Pirbright and which I understand does detect virus.
DEFRA's overkill policies may superficially appear to be a 'safety first'
a) they plainly are not working in this epidemic (for a whole
variety of reasons, not least the apparent inability to maintain effective
and b) they are fearfully ineffecient, damaging and costly
compared to vaccination as a means of controlling spread of FMD virus and
reducing the duration of the epidemic.
This absurd - to my mind - insistence on regaining FMD-free status as
currently defined at whatever cost is just madness.
I suspect just about everybody concerned actually recognises that but that it's politically unacceptable to admit it - Blair (and his Govt) - and others who stand to
lose 'face' - cannot be perceived to have made a mistake so we have to
carry on regardless just to maintain his 'reputation'.
Our comment: We are interested (though not exactly comforted) to see that
Andrew has reached pretty much the same conclusions as ourselves, on the
evidence available so far. We are still pursuing the points about carrier
animals and and inappropriate testing with Pirbright and hope to report back
Meanwhile, Peter of the Soil Association sent us this fascinating item:
On the Today Programme, Radio 4 this morning, Gill once again suggests that
that vaccinated animals pose a risk of re-infection to other non-vaccinated
stock. THIS IS A COMPLETE MISREPRESENTATION OF THE TRUE LEVEL OF RISK. Some
time ago I taped a discussion with Professor David King on Farming Today
[Friday 20 April 2001] in which he is adamant that the risk of infection
from FMD-vaccinated to other livestock is extremely small - negligible...
Typed it up this morning - apols for any typos - hope it's of interest.
Farming Today Friday 20 April 2001
Professor David King, Government Chief Scientist
Miriam O'Reilly (Q) - I asked Professor King if cattle, which are soon to be
turned out on to spring pasture, were vaccinated could they still carry the
Professor King (Prof K) - "I'm very glad you've asked me that question
because I think that there is an enormous amount of misunderstanding on this
very issue. The cattle that are vaccinated with this high-potency vaccine
that is available... would be able to face a very severe challenge of foot
and mouth virus and therefore would not pick up the disease. They would
develop antibodies which would stop the virus going into their bodies and
virus would not go into their milk. The virus is carried but only in the
region of the throat of the animal and the rate of infection of other
animals from an animal which is carrying it in this way is very, very low
indeed. There are one or two reported cases around the world and there's
been a very long history of foot and mouth disease - one or two cases only
where disease has been shown to have been spread from such carriers.
Q: If they can carry disease in their throats does that mean that they could
breathe it out?
Prof K -Yes, but what I am really going to stress here is that because of
the anti-body development in the body of the cow the virus can never build
up to a significant enough level to amount to a significant challenge to
another animal and so the possibility of passing the disease on to another
animal is extremely low.
Q: Science is never an absolute so can you say to farmers that there are no
risks at all with passing the virus from vaccinated animals?
Prof K -You have phrased your question absolutely correctly - science
sometimes does deal with absolutes but when we're dealing with complex
phenomena of this kind we're dealing with statistics and what I've just said
to you is as accurate a statement as I an make. I was in other words a
betting person I would say that from the vaccinated cattle, if we vaccinated
all the living cattle in Cumbrian barns today, from those vaccinated cattle
would bet that we would not spread the disease at all.
Q: Why then do you think the NFU and many farmers who have contacted this
programme are against vaccination?
Prof K - Well let me say that in the last three days I have spent a
considerable amount of time talking to members of the farmers union, talking
to farmers and talking to vets and I've received a lot of extremely useful
information from people who work in the field with these animals and they, I
hope, have received useful information from us. I think there has been, as
always happens in situations of this kind, an awful lot of misunderstanding
about the science of the disease and the question that you asked me about
the carrier state, and the way scientists use the phrase carrier state, is
perhaps the most confusing of all.
Q: Would animals have to be vaccinated continually over that 6-month period,
or would one vaccination do it?
Prof K - This high-potency vaccine being held at Pirbright would only need
to be administered once to a herd and only once and within three to four
days the antibodies would have developed in the animal and we would say keep
the cattle in barns, if they are already in barns, for a week after the
vaccination and when they're let out then the animals exposed to virus would
not become diseased. Now your question is should this be repeated and it is
true that the antibody level in the animals dies off with time and, so
roughly six months later a booster vaccine would be needed if vaccination
was still required. But let me stress that the way the epidemic is going and
the way it is now under control, my belief is that in sixth months time
there would be no need to re-vaccinate these animals because we would be
getting rid of the disease.
Q: And finally, Professor, one last question. Business leaders are saying
that this epidemic could cost the country #40 billion if it's still around
in July - are we going to be in the same situation in July, do you know?
Prof K - We're not going to be in the same situation in July - let me be
uncharacteristically dogmatic about that. I think that when we say that the
epidemic is coming under control, we have a high degree of confidence in
that. Surveillance and culling must continue at the present level but if we
do that then I'm really quite confident that come the summer this epidemic
will be stuttering along but at a very slow rate.
Pat sent this report from Cardiff on Tuesday morning:
We went to the Welsh Assembly this morning,
and sat in while they were discussing. Carwyn Jones seems to be in a
minority of one - he spouted the usual stuff about vaccination, but the
others were saying well let's look into this properly. Even Mike Bates
seems to be coming round. The vets were toeing the government line, but
what do we expect? Ruth gave Carwyn her paper and they disappeared back
into their private rooms with Janet Bailey, so fingers crossed. The
turnout was very disappointing - 7 of us from the Forest, a few from the
Beacons and maybe a smattering of others. I was hoping for hundreds. Have
we all lost heart? The sheep are sure to die if we have.
And Theresa sent us her view of the same events:
We went to the National Assembly yesterday to hear the debate and support
Dr. Ruth Watkins in her appeal to Welsh Government to vaccinate and not kill
the hefted flocks on the Beacons. Tony Edwards, the Chief vet (and also
stated on farming today this morning) reiterated the risk of anibody +ve
sheep maintaining the virus and this mornings speaker said 'and these
healthy animals passing out virus for months. The local veterinary
epidemiologist points out how difficult it is to prove a negative,- ie that
Ab+ve sheep don't shed active virus,- and therefore one has to continue to
kill them. What proof or what research has been done on this?
Unfortunately we had no focus for a nice demonstration with posters,- we
only found some excellent people from Forest of Dean,- others in many
Richard North has further responded to our blood testing correspondence:
I was not suggesting that IgM should replace IgG - merely that it would be a
adjunct. It would be especially useful in the Brecon situation where it
could be established whether the antibody-positive animals had been recently
infected or not. If the animals demonstrated old infection, then the
government's case for destroying them on the grounds that they posed a risk
of infection would be substantially diminished. Then, of course, the true
agenda has to come out - that DEFRA is working to an EU Commission agenda,
order to restore export status.
In this context, the special situation in the Brecons would hardly overload
the system. Has he not heard of couriers, and the telephone. Samples could
be biked down to the lab in hours and the results could be back the same
It seems to me that there is nothing quite so inventive as a scientist on
the public payroll when he is offering excuses for NOT doing something.
And, as for other tests, what about the PCR test?
Lisa sent in this report in response to our item re. Brecon sheep carcases
being rendered at Torrington:
I had a call tonight from Richard Howe at Radio Devon, he told me that the
sheep that have been culled on the Brecon Beacons are coming to Great
Torrington, Devon for disposal by rendering. Then I read my email.
There is a program on the breakfast show tomorrow morning.
If the government had vaccinated to control foot and mouth there would not
be a disposal problem. It is insane to bring rotting corpses to Devon from
Wales, there must be licensed rendering plants and incinerators closer.
Surely there must be a way to avoid the unnecessary health risk posed by
transporting these carcasses.
We know well in Torrington that rendering is preferable to burial after
being ambushed with the burial of up to 50,000 carcasses into Deepmoor
landfill site, and now the ash. We had leaking trucks coming through the
town for weeks both to Deepmoor and the rendering plant.
Great Torrington has had its fair share of being dumped on over the years
and has more than contributed to the problems caused by MAFF/DEFRAs failed
Interestingly, Peninsular proteins rendering plant has not had an operating
license for seven years, yet due to flawed policy is allowed to operate and
infringe on our human rights. Torrington people have been fighting this for
over 20 years.
They lost their license because they could not keep the smell within the
boundaries, then were allowed to continue operating without a license when
they applied for a judicial review. The review was due to be heard this May.
No one can find any information on the outcome and they are still rendering
Apart from the fact that we are forced to live with the smell from the
rendering plant Great Torrington along with other areas in the SW are trying
to recover what is left of the tourist industry this year, now we are in the
school holidays more tourists are coming to the region. Visitors to the
county will not appreciate travelling behind stinking carcass lorries and
Torrington will be stinking for a while.
The whole crisis has clearly been mismanaged from the start, the Government
is desperately trying to avoid scrutiny surely they must at some point admit
they were mistaken and vaccinate now.
What can we do? I'm tired out from protesting. When will someone listen?
I'm talking early on radio tomorrow, hope my brain works!
Julia Currie has sent us the following message and attachments:
I have today sent a Report to all members of the DEFRA Select Committee,
which I presented to my MP (a member of the Select Committee) on Saturday.
It is attached, together with the appendices.
The aim is to stop the slaughter and start a vaccination programme;
initially I am recommending in the Brecon Beacons and other upland areas.
The contents are:
1. Introduction and report purpose
2. Executive summary
3. Economic, financial and numerical costs
4. Effects on farming
5. Environmental considerations
6. Human factors
7. Animal welfare and slaughter
8. Current eradication policy and the alternative - vaccination
9. References, sources and acknowledgements
Many of you have supplied me with sources or helpful information, and I have
referenced the Report as well as possible. Thank you for your help.
Please feel free to use any or all of it if you see fit. I am also
circulating it widely.
Regards - Julia Currie
We asked Julia about the DEFRA Select Committee, and she replied:
Each Ministry has a Select Committee, made up of a group of cross party
MP's. They shadow Ministers and their actions and are supposed to act as a
form of checks and balances (my interpretation). I have been told by my MP,
who sits on the DEFRA Committee, that it/they will not be meeting again
until Parliament reconvenes in the autumn - clearly for them, FMD is not a
This item came in from Lisa at Heart of Devon:
Vaccine efficacy in sheep.
I e-mailed Dr Colin Fink, a leading micropathology to
enquire why the NFU had told me there was a high
failure rate of vaccination in sheep and that they did
not know of any examples of it.
This was the reply
The NFU know nothing about vaccine evidently. This
information about vaccine efficacy in sheep is utter
rubbish. The seroconversion rate in sheep is about the
same as Polio in humans - about 80 - 96% depending on
the skill of the operators...yours Colin.
from Alan & Rosie