(Jeg kan ikke finne denne på KK-Forums websider så jeg sender den på nytt,
selvom kanskje mange har fått den i egen post)
KK-Forum,
Glemte å sende denne for en stund siden (onsdag 21. mars).
Britisk veterinær ("one of B's most prominent vets") om M&K. Fra The
Guardian. Saken er dekket i Stavanger Aftenblad i dag.
http://www.guardian.co.uk/footandmouth/story/0,7369,459445,00.html
Knut Rognes
**************************
Full text: vet's report on animal culls
The following report was sent to the Guardian yesterday. It was written by
one of Britain's most prominent vets who has close associations with the
world foot and mouth centre in Pirbright. It was written for the
independent Elm Farm organic research centre which is preparing a court
case to prevent the giant animal culls planned by the ministry of
agriculture. The author has asked to remain anonymous.
Tuesday March 20, 2001
What is wrong with the current policy?
The infection is simply too infectious under British conditions in high
density stock rearing areas for control by slaughter policy, especially
where the authorities have proven unable to match the short recognition
to slaughter interval used in the 1967-8 outbreak (almost all cases being
slaughtered within 2 days).
The speed of response in many cases can be seen to have contravened
article 5.2(a) of Directive 85/511/EC, which requires slaughter and safe
disposal of the carcasses 'without delay' and with no risk of spreading the
virus. If the authorities are 'overwhelmed' in this process this is seen
as an indication for the use of vaccination (European Commission, 1999).
Council Directive 85/511/EEC, 18th November 1985 (legislation in force 17th
March 2001) European Commission, 1999. Strategy for Emergency
Vaccination against Foot and Mouth Disease (FMD).
http://europa.eu.int/comm/dg24/health/sc/scah/index_en.html
The authorities have mistakenly used the stated incubation period in the
OIE Animal Health Code of 14 days in their predictions of effectiveness
of their policy. The figure of 14 days refers to the maximum incubation
time, a figure needed in the quarantine of premises and is far longer
than the interval between infection of one animal and its ability to
infect another (the generation interval).
The latter is lower in sheep than other stock, therefore the rapidity of
the slaughter response has to be faster than that of the 1967 situation to
be effective. Since sheep with type O strain (as occurs in the current
outbreak) are infective for other sheep and pigs in less than 4 days
(and as many as 25% were infectious at 2 days; Donaldson, 1986; Cox et
al, 1998, Callens et al, 1998), the 14 day incubation can therefore mask
over 3 new amplifying rounds of infection. Each FMD infected animal is
estimated to initiate between 2 and 73 new infections (Woolhouse, 1996),
with the lower end of this range only occurring under dry, hot
conditions with low densities of stock, situations which are far from the
case in sheep flocks in Cumbria. Every delay of 4 days or more enables a
new generation of infective sheep (and/or transmission to other stock) to
occur.
• Cox et al, 1998. Report of the Session of the Research group of the
European Commission for the Control of Foot-and-mouth disease. FAO, Rome,
pp139-143. Callens et al, 1998. ibid, pp129-138. Donaldson, 1986.
Rev.Sci.tech.Off.int Epiz., 5(2), 315-321. Woolhouse, 1996.
Epidemiol.Infect., 363-371.
The current delayed slaughter response favours new infections, and
unrecognised animals with FMD could therefore be expected to result in
between 5 and 50 new infections within 7 days. Airborne spread within the
neighbouring 3-5 km frequently occurred in the 1967/8 outbreak under
'unfavourable' conditions on calm, warm, dry spring days and up to 100 km
under cooler, moist airflows with higher humidity.
The reported delays of 3-4 days from suspicion of infection to slaughter
are therefore too slow to be effective in preventing longer distance
spread, and establishment of infection in new areas. It must be noted that
the longest recorded distance of airborne transmission occurred exactly
at this time of year (the winds of March 7th and 10th), and previous
longest recorded (Denmark to Sweden) also occurred at the latitudes
(54-560N) of Cumbria/south of Scotland (ie climatically very similar).
• Haydon et al, 1997. J. math. Appl. Med. Biol., 14, 1-9.(information also
from other sources) Donaldson, A.I. et al, 1982. Veterinary Record,
110, 53.
The epidemiology of FMD involving sheep is far too uncertain to have
confidence that a mass cull within 3 km would be effective, or
scientifically justified. In the FMD epidemic in Greece in 1994 the
infection in sheep 'faded out' although control measures were poorly
implemented. (Callens et al, 1998, Kitching, 1998).
In the Macedonian outbreak of 1996, FMD infection entered sheep
subclinically and as many as 50% sampled 2 years later had evidence of past
infection, but again this source did not result in the outbreak
perpetuating itself. Experimental studies suggest sheep produce
relatively little virus for onward transmission (compared to cattle, and
over 1000 times less than pigs; Sellers, 1971) and are often poor at
perpetuating infection by contact. The cull of sheep is therefore not
supported by evidence whereas extremely active control of pig and cattle
infections are.
However the 'fade-out' scenarios mainly occurred under hot, dry
conditions, (with the exception of Tunisia in 1989), whereas under cool,
moist conditions, with overcast skies, long distance spread over land
(1-100 km, beyond the restriction zones) is possible ), particularly from
cattle and pig sources, and has already thought to have occurred in this
outbreak (Vet Record, March 9th 2001).
Further, since sheep are the most sensitive species for becoming infected
with virus, there is simply no information available on how many animals
have become infected within or beyond the 3 km restriction zones,
especially those which may have received windborne virus from the first
infected pig farms. It simply cannot be concluded that infection has been
restricted to areas planned for the cull.
• Sorensen, K.J., & Naletoski, I. (1998). Report of the Session of the
Research group of the European Commission for the Control of
Foot-and-mouth disease. FAO, Rome , pp 176-181. Callens, M., et al. 1998.
ibid, pp 129-135. Kitching, P. 1998. A recent history of FMD. J. Comp.
Path., 118, 89-108 Sellers, R.F 1971. Quantitiative aspects of the spread
of FMD. Vet. Bull., 41, 431-439.
The UK mass cull, therefore, unless it had occurred much earlier and
involving all cattle and pigs in the restricted zones would be nowhere
near sufficient to prevent infection in cattle and sheep beyond the 3 km
radius. Since clinical screening in sheep is so poor a guide to
recognition (Callens, 1998, ref above), almost certainly the cull would
be a temporary measure and a prelude to later larger culls (which would
be very vigorously opposed) in the areas beyond the 3 km restriction,
and/or the later use of vaccination.
What are the effective alternatives?
An emergency vaccination strategy, with stamping out of infected cases, was
vigorously promoted and financially supported by the EU and was very
effective in the control of type A FMD in Albania (Berlinzani et a, 1998)
and neighbouring Macedonia in 1996, with elimination of outbreaks within
12 weeks and 3 weeks respectively. The former was the first outbreak in
the region and therefore international responses were delayed; in the
latter an area as large as Cumbria was involved and 120,000 cattle were
vaccinated, and 4,500 cattle destroyed.
• Berlinzani, A, Brocchi, B.,& Simone, F. (1998). Report of the Session of
the Research group of the European Commission for the Control of
Foot-and-mouth disease. FAO, Rome, pp166-175. Sorensen, K.J., &
Naletoski, I. (1998). Ibid, pp 176-181.
Emergency vaccination is an approved form of FMD control in Europe and
there is significant preparedness to mount an effective vaccine based
response, which MAFF and the EU has been funding for at least 15 years.
A decision to use emergency vaccination is very likely to be approved
without delay by the European Commission since the current outbreak meets
almost all the criteria outlined in their policy guidelines (European
Commission, 1999):
A high density of susceptible animals, (Cumbria, Dumfrieshire, mid-Wales
and west Devon have very high ruminant densities favouring rapid
transmission.)
An infrastucture that is capable of rapidly deploying vaccination (we have
highly motivated and technically competent farm staff used to vaccinating
their own animals and hundreds of veterinarians and veterinary students
available to undertake the work)
Predicted airborne spread of the virus (a situation that favours the use of
vaccination). Although pig farms are less involved in the current
locations, climatic conditions favour airborne spread from cattle farms,
which paradoxically are not destined for the proposed cull.
A suitable vaccine exists (there are at least 500,000 doses (equal to
1,000,000 sheep doses ) of type O vaccine at Pirbright, UK and about 10
million in the European Vaccine bank).
The incidence slope; new outbreaks are occurring daily (a rise to a record
of 37 new cases on 17/3) and a very significant reservoir of infection is
still present awaiting slaughter, capable of generating new waves of
infection.
Distribution of outbreaks; widespread outbreaks are seen as an indication
for vaccination (29 counties, 17th March). However the main foci could be
surrounded by an immune barrier by ring vaccination, an approved EU
approved strategies (see below).
Public reaction to stamping out; a significant negative reaction is seen as
an indicator for vaccine use, since the reaction would be damaging to
eventual control (non-compliance) and international opinion to Europe
Likelihood exists of the European Commission request for regionalisation of
the vaccinated population; the position of the comittee which framed the
Report was that there would be no reason to refuse a request to
regionalise the outbreak by vaccination if 1) the disease control measures
would be fully enforced, 2) the protection and surveillance zones are
subjected to strict controls, and 3) the control of movement of animals
and their products is effective, each of which can be expected to
demonstrably be the case with current EU opinion on MAFFís capabilities.
Another indication for vaccination is 'an overwhelming of the capacity to
kill and dispose of carcasses within a short time period' (ibid, p 5);
patently the case in this outbreak where the delayed slaughter and
disposal brings a risk of onward transmission. European Commission,
1999. Strategy for Emergency Vaccination against Foot and Mouth Disease
(FMD).
http://europa.eu.int/comm/dg24/health/sc/scah/index_en.html
However, what the Emergency Vaccination report fails to consider is the
value of prevention of virus entry into hill sheep and wildlife
populations in upland areas: this should be a strong indicator for
vaccination, since a huge cull (in effect, total depopulation) if control
by slaughter is the only option.
What are the advantages of emergency vaccination
Emergency vaccination is of proven use in FMD control (European Commission,
1999, Salt, 1997). It can be used in two ways, simultaneously or
separately; to create an immune barrier ('ring' or 'belt' vaccination,
creating immunised zones) to prevent spread through populations at risk
from airborne or local spread of infection, or to 'dampen down' infection
within known FMD infected areas where there is a recognised urgent need
to reduce virus transmission and to prevent onward spread beyond the
restricted area.( European Commission, 1999, p5).
Rapid reduction in virus circulation and new cases; as noted for Macedonia,
effective and rapid deployment of vaccination reduced the total period of
reported FMD cases to 3 weeks, despite over 18 villages in two districts
being involved and avoided establishment in the sheep population of the
region.
Vaccination limited the slaughter to only 4500 animals. It is capable of
enormously reducing the risk of airborne and vehicular spread to
unaffected areas, vastly increasing public confidence within and outwith
restricted areas in the control process. Vaccination is also seen as
ethically and publically acceptable, a rational response to an
exceptionally infective condition and which has a very rapid response.
Public acceptance, and farming compliance would be expected to be
exceptionally high compared to mass culling.
The activities can be undertaken by personnel who are not in short supply
(as are veterinarians at present); most farmers could undertake, with
brief training and with additional support (veterinary students are one
resource). It enables valuable germ-plasm to be saved. The current
culling policy is unacceptable for its impact on rare breeds and high
genetic quality stock; emergency vaccination can enable this to be
mitigated.
Present recommendations under the rapid system (3 months) for regaining
FMD freedom require that vaccinated animals are slaughtered. This would
give a short opportunity before slaughter to enable germ plasm
(particularly semen) to be collected and stored, which could be later be
tested with internationally approved tests (ie in the OIE Manual of
Standards for diagnostic tests) recommended for FMD freedom in germ
plasm, and later used in re-establishment of the breed line. If vaccinated
animals were not slaughtered, a 12 month period would need to elapse after
the last case before international recognition of live trade.
• Salt, J. (1997). Vaccination against FMD. Veterinary Vaccinology,
Elsevier Press. pp641-649.
An effective vaccine is available and approved for emergency use. Two
banks of vaccine for emergency use occur in the UK, the International
vaccine Bank and the European vaccine bank, both held at Pirbright (the
latter bank has also deposits of vaccine in 3 other countries). These
banks have 0.5 million and 10 million cattle doses of suitable O type
available, which translates to about 22 million sheep doses. Callis, J.J
(1997). Problems of vaccine distribution (vaccine banks). Veterinary
Vaccinology, Elsevier Press. pp703-704.
The aim of vaccination is two fold; to protect stock against the disease,
but of even greater significance to the national herd, to vastly reduce
the proportion of animals which could amplify virus to a point where it
is unable to create new cases and naturally does out, or more as required
the limited cases can be detected and stamped out.
The proportion of each flock herd to be effectively immunised must be at
least 70%, preferably at least 80% (Salt, 1997; and Professor Ahl,
Tubingen, formerly Chair of EU Animal Health and Welfare Ctte, FMD
Emergency vaccination working group); a very achievable figure in the UK
where very high compliance is expected, and in such an emergency as this it
would be expected that farmers would be anxious to achieve near 100%
vaccination rates. It is often said that the FMD vaccine is a poor one,
and therefore emergency vaccines are specially formulated to achieve high
and rapid responses (below). Salt, 1997, reference above.
These emergency vaccines have a high "payload" in order to be rapidly
effective as a single shot; they have been shown to be effective as early
as 3 days after immunisation, in prevention of infection and disease,
within between 4 and 7 days all immunised cattle and sheep being prevented
from becoming 'amplifiers' capable of onward transmission. (Cox et al,
1998, Salt et al,1997) This period is shorter than the period between the
proposed cull and the expected start of the slaughter!!! Further high
payload vaccines are considered effective against almost all strains of
the virus type O, therefore expected to be effective in the UK epidemic.
• Cox et al, 1998. Report of the Session of the Research group of the
European Commission for the Control of Foot-and-mouth disease. FAO, Rome,
pp139-143 Salt et al,1997, Vaccine 16,7, 746-754
Vaccine delivery to farmers in Cumbria would in my opinion be expected to
result in near 100% vaccination rates within 5 days, and almost complete
herd immunity in 10 days. A reduction in cases to nil could be expected
within 3 weeks, although restrictions and the few remaining incubating
cases that remain.
The ramifications for farmers of emergency vaccination are almost certainly
better than the current culling policy; but depend on whether MAFF opts
for one of the following options: Vaccination in the restricted zones to
prevent transmission and risk to surrounding areas, followed by slaughter
of vaccinated animals and active cases. This would enable a return to FMD
free status in 3 months under the OIE Animal Health Code (see:
www.oie.int), and despite the apparent severity of the requirement that
vaccinated animals would be eventually slaughtered, the latter could
occur in a progressive, orderly manner , allowing germ plasm from very
valued blood lines to be stored for later re-stocking/breed resuscitation,
and be more acceptable locally than mass culling.
The vaccination could be restricted to sheep and pigs, since they have
the principal risk of rapid virus amplification and disease is more
difficult to detect. Fewer herds would therefore require emergency culling
and the outbreak should be curtailed in 3 weeks. Vaccination in the
restricted zones, plus ring vaccination to prevent onward transmission;
more effective at outbreak control, but if vaccinated flocks/herds would be
culled the impact on 'healthy' flocks would be high and apparently
nonsensical.
However in national terms, return to free status would be regained after
3 months of disease freedom and after cull of the last vaccinated animals.
Vaccination as (b) but without culling of vaccinated animals unless FMD is
diagnosed as present in the herd/flock; under this system return to free
status12 months after the last case of disease.
The economic loss associated with loss of the livestock trade is seen as
the 'strongest argument against implementation of emergency vaccination'
(European Commission, 1999) but needs to be set against the economic loss
to other sectors (tourism etc) Vaccination would hugely reduce the
compensation package, greatly reduce the compensatory loss of during
re-stocking, and the cost of rural aid programmes after the outbreak.
Importantly it would reduce the length of time from current to the last
case of infection, which could be 2 months or longer (as it was in the more
restricted 1967 outbreak) under the culling system or about 3 weeks under
vaccination scenario.
How quickly could movement of vaccinated animals be resumed, once disease
is controlled?
Free movement of vaccinated animals from free areas should be permitted is
logical (European Commission, 1999), and the report provides criteria for
animal movement after vaccination. It can be assumed to be resumed from
60 days after the completion of the emergency vaccination, provided that
an effective and reliable surveillance system is in place aided by the
recent tests that distinguish animals which have met virus from those
which are merely vaccinated (Panina and Ahl, 1998), Working group on
Emergency Vaccination, EU Animal health and Welfare Ctte, 1998).
• Panina and Ahl, 1998, Working group on Emergency Vaccination, EU Animal
health and Welfare Ctte, Report of the Session of the Research group of
the European Commission for the Control of Foot-and-mouth disease. FAO,
Rome, pp276-278 European Commission, 1999. Strategy for Emergency
Vaccination against Foot and Mouth Disease (FMD).
http://europa.eu.int/comm/dg24/health/sc/scah/index_en.htmle
Doesn't vaccination interfere with our FMD free status?
European policy of non-vaccination has the objective of creating a European
herd which is without evidence of antibodies to FMD virus, since the
latter might indicate animals which carry infection after exposure. Since
antibodies can also arise from vaccination, very considerable effort has
been made in the 1990's to develop tests that distinguish antibodies
resulting from those from infection.
At least 5 different tests have been developed and validated (an entire
European Union funded Concerted Action was devoted to this-research
summarised in over 15 papers in the supplement of the Vet Quarterly,
1998, 20, suppl 2) and these now transform our ability to distinguish
vaccinated animals which have not met the infection, and they can
identify the important category of those which have been vaccinated in an
emergency situation and subsequently become infected upon severe virus
challenge.
The international recognition ('standardisation') of these tests for the
purposes of international trade is ongoing, and the Scientific Ctte of the
European Commission was 'of the opinion that the application of NSP-tests
allows for an earlier lifting of the restrictions on the movement of
vaccinated animals'. Changes to the Animal Health Code of the OIE in
respect of testing vaccinated animals as part of the process of regaining
FMD freedom, and are under consideration by the OIE, Paris. Amendment of
the Animal Health code could occur within 2 months, given the strong
European consensus on the use of these tests.
Therefore at WORST with emergency vaccination UK exports would be curtailed
for 12 months; at best the period could be as short as 3 months after the
last case has been slaughtered if the OIE Animal health code was amended
this spring.
Example peer-reviewed papers; Bergmann, I.E., et al, 2000. Improvement of
a sero-diagnostic strategy for FMD virus surveillance in cattle under
systematic vaccination, Arch Virol., 145 (3), 473-489. Sorensen, K.J.,
et al. 1998. Differentiation of infection from vaccination in
foot-and-mouth (shortened title). Arch Virool, 148 (8), 1461-76.
In other words, if DG-Agriculture was to follow the recommendations of its
Scientific Committee and recognise the use of the post-vaccination
surveillance system (something it could do in days), and at a later date
at its annual meeting this spring the Office Internationale des
Epizooties in Paris (OIE) was to amend its animal health code, then FMD
free status could be rapidly regained by vaccinated herds without a need
for culling, unless shown to be infected.
This decision could well be made in the next few weeks if MAFF pressed for
it and would completely change the economic arguments (effect on
livestock trade) against vaccination.
With current regulations emergency vaccination conducted by an effective
veterinary service with stamping out of remaining active cases, would at
worst result in 12 months loss of the export trade. Surely MAFF should
consult with the NFU and other bodies to determine if they would accept
this financial loss rather than the enormity of the proposed regional cull.
***************************
This archive was generated by hypermail 2b29 : Tue Mar 27 2001 - 16:12:57 MET DST