Fwd: Foot and mouth - the truth

The Land Is Ours office at tlio.demon.co.uk
Sun Mar 25 22:37:59 BST 2001

>Originally sent by: oliver at aycaramba.co.uk
>To: ecohousing at egroups.com
>Date: Tue, 20 Mar 2001 19:38:34 -0000
>Foot and Mouth disease
>Why we should vaccinate - from <http://www.sheepdrove.com>www.sheepdrove.com
>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 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 animal 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) 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 and has already thought to have occurred 
> in this outbreak (Vet Record, March 9th 2001), particularly from cattle 
> and pig sources.
>    * 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 establishment in hill sheep (and other stock) 
> beyond the 3 km radius, and 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 vigourously 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. Nevertheless 
> the period from first recognition to last case was less than the period 
> elapsed in the current UK outbreak
>    * 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 (Panina and 
> Ahl 1998):
>        * A high density of susceptible animals, (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)
>        * 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 and a 
> very significant reservoir of infection is still present capable of 
> generating new waves of infection
>        * Distribution of outbreaks; although currently many counties are 
> involved, the major areas are restricted and vaccination could occur 
> within or around these under 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
>    Further, this committee considers 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 MAFF’s 
> capabilities.
>    Panina and Ahl 1998. Emergency vaccination against Foot-and-Mouth 
> Disease; a short review of the activity of a specific working group of 
> the European Commission. Report of the Session of the Research group of 
> the European Commission for the Control of Foot-and-mouth disease. FAO, 
> Rome, pp276-278.
>    * What are the advantages of emergency vaccination
>        * Emergency vaccination is of proven use in FMD control (Panina 
> and Ahl, 1998, ref above; 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.(Panina &Ahl, EU "Animal health and 
> Welfare" committee outline of policy, 1998).
>        * 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 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!!!
>        * 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 needs to be set against the 
> economic loss to other sectors (tourism etc), it would hugely reduce the 
> compensation package, it would greatly reduce the compensatory loss of 
> during re-stocking, 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?
>    * Movement could 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
>    * 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 DG-SANCO of the 
> European Commission is currently revising the recommendations on the use 
> of vaccination to incorporate these technical advances. This committee is 
> due to report shortly, and since it is likely that they will recognise 
> the use of these tests in clean herds after vaccination, that policy will 
> change to allow freedom from FMD to be regained after surveillance for 
> infection in vaccinated animals (Panina and Ahl, 1998, ref above), at a 
> much shorter waiting period than with the current.  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-SANCO ( and later the Office Internationale des Epizooties in Paris 
> (OIE)) was to decide tomorrow that these tests could be used in herd 
> surveillance after vaccination, then vaccinated herds would not need 
> culling unless shown to be infected. This decision could well be made in 
> the next few weeks and would completely change the economic arguments 
> (effect on livestock trade) against vaccination.
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