Other Strategies for vaccination
The Soil Associations Strategy for vaccination
Summary
- A vaccination programme used in conjunction with slaughter on infected farms provides the best hope of getting the disease under control
- Giving farmers an alternative to slaughter in the firebreak zones is the only way to regain their confidence
- The vaccination strategy should be applied in all infected regions in the UK, not just Cumbria and Devon. Only hefted ewes in hill farming areas should be excluded.
- It is essential to start vaccinating immediately - days count
- All species of stock should be vaccinated in the firebreak zone farms
- Only the livestock in infected herds and exceptionally 'at risk' farms should be slaughtered in future
- Vaccinated animals can and should go into the food chain
- Vaccinated animals should not be subsequently slaughtered - it is unnecessary
- It will still be possible for the UK to regain disease-free status in a post-vaccine scenario.
Q. Where should vaccination be used?
Vaccination should replace the present slaughter policy in the so-called firebreak zones up to and including farms adjacent to infected farms
- It should be introduced immediately
- Vaccination should be used in all regions of the UK, starting as a ring around infected areas and spreading outwards to cover all regions, ie there should be a structured national vaccination programme
- Vaccination should also be considered as an option within infected holdings if farmers can show that flocks or herds on that holding have had no physical contact with infected animals
- Farmers in firebreak zones who have already been told their animals will be slaughtered should be offered vaccination as an alternative, with immediate effect.
Q. Which species of animal should be vaccinated?
- All cattle including calves
- All sheep including lambs over one week old
- Pigs where appropriate (for instance, in free-range, outdoor herds and with rare breeds) including piglets over two to three weeks
Q. Where is it not appropriate to use vaccination?
- On hill farms where the ewes are hefted. In these cases, if the disease is present, rounding up the ewes and vaccinating them would be counter-productive as it would spread the disease further. It would be better to leave them alone as at very low stocking rates, the disease will fade out naturally.
- Is there still a place for slaughtering uninfected herds?
- This should only be considered in cases of extremely infected areas where it is considered inevitable that the herd or flock will be infected.
Q. Could vaccinated herds/flocks still get the disease?
- If the disease is already incubating when vaccination occurs, then animals will still come down with the disease. This needs to be explained to farmers - ie they need to be told when vaccinating their animals that if any of them should subsequently show clinical symptoms the entire herd/flock will have to be destroyed.
Q. Should vaccinated animals subsequently be slaughtered?
- Absolutely not!
- Vaccinated animals can and should go into the food chain
- Milk from vaccinated dairy cows can and should go into the food chain
- Keeping breeding stock which have been vaccinated alive could prolong the period before the UK regains disease free status but this problem should be addressed later
- It is essential to put out a clear message that all vaccinated animals will not subsequently be slaughtered. Without this, there will be major opposition to the policy.
Q. What about the long-term prospects for the UK regaining disease-free status in a vaccination scenario?
- It is not possible to predict how long this will take in the present circumstances, but continuing with the slaughter only policy is unlikely to bring this date forward - the UK can still regain disease-free status twelve months after the last clinical case of the disease and/or the last animal has been vaccinated. At present it may be that if the foot and mouth problem worsens in other EU Member States then the UK will not have this problem anyway.
- What effects does a delay in the implementation of the vaccination strategy have?
- The overall rural economy is far more important than regaining our export capacity
- Every day delayed means another 20 to 30 farms will become infected at the present rate of contagion
- This means another 12,000 to 18,000 animals per day could succumb to the disease
- Every day without vaccinating means one day nearer to lambing for those who have not already started
- Another day closer to turning the cattle out (within the next few weeks) and once they are out, the disease could then spread as rapidly through the cattle as it has done with the sheep.
Soil Association
Bristol House
40-56 Victoria Street
BRISTOL BS1 6BY
0117 914 2442
March 2001
*******DRAFT VERSION*******
Introduction
-If there is a wholesale cull of animals from the Brecon Beacons and other common land the environment will change to scrub and require different management to retain diversity and biohabitat.
-If infection spreads down to farms around the beacons we could face a winter of slaughtering out on a scale like that in Cumbria or Devon in a resurgence of infection following the return sheep to winter pasture. Further degradation of the environment will take place with the problem of disposal of 100,000s of carcases.
-If we cannot resolve our crisis quickly the summer season for tourism and the welfare of farmers and their animals will be severely affected by the lack of income. Can we as a community survive this?
Definition of terms
The commons comprise the Eppynt, the Brecon Beacons National Park, the Black Mountains and the ‘Brecknock’ and any other common land in South Wales
The vaccine used would contain serotype O Manisa subtype (the Pan Asia subtype has not been adapted for vaccine production on a commercial scale and this vaccine works well e.g. in Holland). This vaccine contains inactivated, "killed" virus, and is safe and efficacious to use. The vaccine does not infect the vaccinated animal; the vaccine acts as a protein stimulating the immune system to produce protective antibody. If an animal has already been infected with FMD virus serotype O (our epidemic strain) then the vaccine achieves nothing but does no harm to the animal.
Vaccination consists of a primary course, 2 inoculations 3 weeks apart. If the oil-based vaccine is used then almost 100% of animals respond and antibody will be present at a high level a week after the primary vaccine course is completed. A third inoculation at 6 months can be given to ensure a good level of protective antibody for one year. This applies to domestic animals receptive to FMD infection, sheep, goats, cattle, pigs, deer and water buffalo.
If the high potency vaccine is used then only one shot is necessary rather than 2 in the primary course. The animals could be released to the commons 3 weeks after vaccination. However I think we should leave the high potency vaccine for use in the hot spots in the North and South of England- we could use the commercially available vaccine licensed for use in the UK (use allowed only with the permission of the government)
The presence of infection on a holding
is defined as animals experiencing acute infection with FMD. An outbreak is a chain of acute infections. Finding an antibody positive animal that is healthy on a holding amongst other healthy animals does not constitute prima facie evidence for the presence of infection. In this case it should be sought by sending specimens to the laboratory for virus isolation. Meanwhile vaccination can be applied removing the need to kill in haste. Some antibody positive animals might be carriers, and these would be expected to be positive for FMD viral RNA in the ‘farmgate test’ or by PCR. The tests for viral RNA will become negative when they cease to carry virus.Susceptible = never infected and unvaccinated
Past infection = antibody positive and virus negative by isolation and tests to detect viral RNA
Carrier = antibody and viral RNA positive but virus isolation negative (also evidence of infection >3 weeks ago)
Acute infection = antibody negative and viral RNA and virus isolation positive, or all 3 tests positive.
Plan
Action Management Reason 1. Vaccinate all receptive animals now on the commons (these are few as yet).
Herd them into pens on the commons to vaccinate there. Tag each animal with the owners herd number and an individual number.
Cattle can have a veterinary inspection.
Draw blood and give the first dose of vaccine.
In 3 weeks round them up again on the common, pen them on the common and give 2nd dose of vaccine. (No need to await lab results)
Keep these animals on the common for at least 4 wks after starting vaccination.
Every animal is traceable Every blood sample can be traced toa particular animal.
2. Vaccinate all receptive animals to be released onto the commons, both young and adult animals. Vaccinate them wherever they are held (in tack or on the farm) as 1 above at the same time as those on the commons. 1 week after the primary course of vaccination is completed the animals can be moved onto the commons.
They can be walked on roads and paths.
Again every animal and blood sample is traceable. There could not be any infectious animals among these 4 wks after commencing vaccination so they pose no significant risk travelling to the commons.
3. Leave all animals on the commons for at least one further month before moving off the commons. This will allow the degradation of any environmental contamination of virus on the commons so that virus is not brought back on hooves etc to the holding.
The purpose of the plan
The graziers can safely graze their flocks and herds on the commons in the knowledge that further spread of infection will not occur. Fodder and pastures for wintering animals can be set aside. However we need to act quickly now. Movement and marketing of animals can be scheduled for the autumn, and sooner (see below).
Recurrence of FMD in the autumn will be avoided. Without vaccination this could occur when ‘silently infected’ sheep (acute asymptomatic infections in unvaccinated animals) are moved back from the commons. Also a carrier animal under stress may reactivate the virus to a level where it can infect a susceptible animal it is in contact with. This is a rare occurrence but surrounded by vaccinated animals this cannot happen.
Finding antibody positive animals
It is likely also that some antibody positive animals will be identified from analysis of samples taken whilst the animal was on the holding. The discovery of antibody positive animals will be retrospective, as it will take several months for all the serology to be completed.
It is likely that antibody positive animals, some of which may have had an acute infection at the time of release and therefore had been infectious, were released onto the commons before vaccination. However they will not give rise to a continuing chain of infection because they will be surrounded by vaccinated animals. Vaccinated animals even if subsequently infected through exposure to a very high dose of virus (not likely anyway on the commons) have not been shown to spread the infection to other animals whether these are vaccinated or unvaccinated. Also they will have cleared the acute infection (this takes 3 weeks) by the time they come back to the holding from the commons so they will not be infectious though they may be a carrier (see below).
Action for holdings with antibody positive animals
Measures should be taken to determine whether there is still active infection (acute infection) on the holding. Rather than destroy all the evidence without clarifying the situation scientifically it is most informative to obtain the samples for analysis to detect the presence of virus (a PCR test, the ‘farmgate test’ and virus isolation) as well as check the receptive animals on the holding for virus specific antibody.
The opportunity can be taken to vaccinate all the receptive animals in the manner of 1. above. There is no need for immediate slaughter of any animals unless a cow or pig is so ill that the owner and vet agree to it on grounds of mercy. Use of vaccination and quarantine (biosecurity and restricting movement) will contain the infection. Aerosol spread greater than 100 M has hardly ever occurred with this virus strain in this epidemic.
Movement of animals and fomites have been the most important routes of spread of infection. MAFF, by slaughtering animals and disposing of them together with all their kit moving from farm to farm and past farms near the road, have created contamination of the environment with virus and been responsible for the spread of infection despite all their measures. Slaughtering acutely infected unvaccinated animals ensures heavy contamination as virus is in the blood, muscles, secretions and excretions.
If it is judged that a sufficient number of animals are infected to create aerosol that is windborne then slaughtering immediately is indicated. However this has hardly been the case so far in this epidemic (the number of simultaneously infected animals of which species and the distance of spread can be listed for reference). It is much safer to let the animals own immune system control the infection whilst surrounded by vaccinated animals that cannot be infected at all or have a very limited infection which they cannot pass on to another animal. Slaughtering carrier animals on the farm, particularly carrier cattle can be done later. The carcase is not infectious except the mouth; a plastic bag could seal that. When the dead carrier animal is taken to a rendering plant it is not likely to spread FMD infection by contaminating people or the environment with infectious virus. Cleaning up the farm according to the EU regulations can be done when the phase of acute infection is over. By the time an antibody positive holding is picked up few are likely to have acute infections still current. The EU may oblige us to slaughter out holdings where there is proof that acute infection is still proceeding.
The contiguous holdings and dangerous contacts can be tested and vaccinated in the manner of 1. above as well as taking samples for virus detection. Again no animals need be slaughtered immediately.
A protection zone for vaccination and another for surveillance can be defined guided by the EU directives around each farm where the presence of infection was shown. If the infection was proven to be no longer active on the index holding then vaccination in the protection zone may not be necessary, but simply surveillance- both clinical and blood sampling. Some antibody positive holdings will have no carrier animals, each positive animal representing a past infection in which the virus has been cleared. Thus infection cannot be said to be present on such a holding.
Carrier animals
After the phase of acute infection when the virus is widespread in the body, the virus infection is limited by the immune response. Either all virus is cleared within 3 weeks or some animals remain persistently infected for a period of time- the carriers. In carriers the virus is confined to cells in the oral cavity and cell free virus that is shed is complexed to neutralising antibody (the protective antibody). Virus is no longer present in the muscle or blood. Serotype of FMD virus and species of animal affect the biology of infection and persistence so a description needs to be very specific to be accurate.Carrier cattle infected before vaccination are the greatest problem because about 50% of cattle remain carriers and remain so for 3 years or more. Virus may be shed from less obvious locations such as the urine as well as the mouth. It may be necessary to slaughter carrier cattle. Special animals (rare breed, zoo, pedigree, hefted etc) can be checked for the presence of virus (at least 3 samples should be taken) and possibly saved. If the presence of virus cannot be confirmed then they are not carriers. It is better carrier cattle are slaughtered on the farm where they have been retained to make sure the infection cannot spread further.
There is little detailed study of sheep as carriers compared to cattle. Sheep clear the virus within 9 months, only 5% of sheep carrying the virus for 9 months. If carrier sheep infected before vaccination are kept within their vaccinated flock and not moved there can be no reason to slaughter them. As long as we are not allowed to export because we have lost FMD-free status we might as well retain carrier sheep that are to be used for breeding.
Vertical infection from carrier mother to her offspring does not occur except in wild Cape buffalo in South Africa.Movement of animals
Antibody positive animals, sampled before vaccination, should not be moved from their holding (except to the commons) so that they are kept in circumstances where they are surrounded by vaccinated animals. Even if the infectivity of carriers is a rare event the virus can spread no further and cause no new infections. They may be kept until they are no longer carriers, but in the case of many cattle they will have to be slaughtered if we are to regain our FMD-free status 3 years from now.Antibody negative animals from a holding where an antibody positive animal is identified could have the new test for non-structural antibodies done. If this was negative (the animal is already vaccinated so the usual screening test would be expected to be positive) then there was no evidence the animal had ever been infected and that vaccinated animal could be moved.
Animals can be moved from holdings on which all animals screened were negative for antibody before vaccination, provided sufficient sampling has been done in accordance with EU directive 2001/295 annex 2.3.3 (e.g. a 95% certainty of detecting 5% disease). Even if they have been put out on the commons they can still be moved because any animals infected after responding to vaccination do not pose a danger of infection to other animals whether these are vaccinated or not.
Marketing
In Britain we accept that we have lost our export markets for several years whilst first we control FMD and then show that we have eradicated FMD virus from the country. I am not sure if we can create FMD free zones in Britain. Accepting that we will not get FMD-free status back within 3 months of the last confirmed case we need to develop a plan to ensure eradication of FMD in Britain and a modus vivendi for ourselves. The rules the EU has set us in the Commission decision of 30th March do not offer us a way of living through our prolonged crisis. We need to compromise on animal movement within Britain and the labelling of products from vaccinated animals (none to be offered for export) see annex III 1. (b) and 2. 3rd paragraph. It may be that these measures that were agreed in March were formulated on the premise that we would soon be disease free and regain our FMD-free status 3 months later.
- Vaccinated meat is safe to eat and does not need to be labelled as such (likewise for other vaccines).
- Milk from vaccinated dairy cows is safe to drink (likewise for other vaccines).
- Any unvaccinated animal from a screened and antibody negative holding can go to market.
- Vaccinated animals from antibody negative holdings can go to market.
- Vaccinated animals that have not been infected from antibody positive holdings can be sent to market. This would be more than 21 days since the last acute infection by the time the testing is done. An additional period for virus degradation in the environment would be allowed before moving the animals. I believe 4 weeks would cover this. The EU may insist on 3 months
Summary
This plan prevents the spread of infection among sheep and cattle on the commons. It prevents infection reaching the holdings around the commons and a resurgence of infection in the coming winter. There will be economic advantages for the area. All paths can be opened, tourism will also be fully open for the summer season (including horse trekking etc.) with no more pyres, heaps of dead animals and transport to burial sites etc to put them off. Also for farmers the vast majority of their stock will be conserved, they will be able to send animals to market this autumn and plan for sales and shows. Carrier cattle, carrier lambs and surplus small mountain lambs will in all likelihood have to be culled. This can be done in a controlled fashion taking carcases to rendering plants.Not least is the wealth of scientific data that will emerge on the area, and the observations that can be made on carrier animals. The vaccination strategy will be tested and can be costed in detail to compare with what has gone before and to plan an effective strategy to manage the next outbreak in a modern scientific way. Investment in veterinary medicine and veterinary laboratories is a much better use of money than wasting it on slaughter and all it entails.