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FOOT-AND-MOUTH: Eradication versus Vaccination

by 5m Editor
2 March 2001, at 12:00am

As the foot-and-mouth epidemic spreads to all corners of the United Kingdom, thePigSite.com Editor, Jim Muirhead asks the sites veterinary consultants to explain why the Government is pursuing an eradication policy when a vaccine for foot-and-mouth is available.

The Virus

Foot-and-Mouth is a highly infectious disease caused by a very tiny virus. There are seven main types of the virus and within each type there are a number of different sub-types. Infection arises from inhalation or by mouth. The incubation period is usually 2 - 7 days but it may be longer for the disease to be recognised.

The virus is very easily spread and can infect huge areas in only a matter of days if strict precautions are not taken. It can be spread on the wind, up to 35 miles over land and 180 miles over water. Other means of spread are by infected animals themselves, other animals that may not be infected but can carry the disease and mechanical movement of the virus either via transportation, contaminated clothing or footwear. Infected pigs are a particular problem as they excrete huge amounts of virus when breathing.

Foot-and-mouth tends to be a winter disease due to the fact it is not so virulent in warm conditions. The virus is easily killed by disinfectant or mild acidic conditions. Sunlight also kills the virus.

Its initial affect on animals

The disease affects all cloven-hoofed animals including cows, sheep, pigs and deer. Initial signs of the disease include severe lameness, sores and blisters on mouth, tongue, nose and feet. In cows you also see slobbering, shivering, raised temperature and a drop in milk yield. Mortality is low.

As the disease develops the animal suffers significant pain. Blisters form on the upper edge of the hoof, where the skin and horn meet, and on the heels and in the cleft. These can extend right round the top of the hoof. Eventually the blisters burst leaving raw exposed flesh, with the result that the horn becomes separated foot. In cattle the disease causes severe blistering of the tongue, which often peels away leaving exposed raw flesh.

Its subsequent affects on animals

Although animals do not necessarily die, the scars of the infection remain and the animals welfare is significantly compromised. The horn of the foot will start to re-grow, unfortunately this is slow and the horn will grow back deformed, making it difficult and painful for the animal to walk.

The blisters and sores on the mouth and tongue make it very painful for the animal to eat and drink, particularly cows. This results in animals losing condition, adding to the pain and suffering.

Economic implications of the disease

All the stress and trauma from contracting the disease has a major effect on the farmed animal. Cows suffer a significant drop in milk yield, that will never recover fully. Piglets may die, and animals become unthrifty and depressed. Growth rates slow. All this results in a large drop in economic performance which in today's highly competitive global market place puts the affected farmers at a significant disadvantage, and possibly out of business.

Vaccination

Firstly, it is important to understand there is no treatment for foot-and-mouth. Vaccines are available but as there are so many distinct strains of the virus its effectiveness can be compromised. To be effective the specific strain of the virus has to be identified and a vaccine produced to match. This vaccine will not provide immunity against a different type or sub-type.

Additionally the immunity an animal gains from the vaccine is not long lasting. Animals would need to be vaccinated twice a year for ever more, at significant economic cost.

A further problem is that pigs do not respond well to vaccination leaving some exposed to the disease. In an endemic situation a number of pigs would catch the disease and have to be culled.

In some outbreaks "ring vaccination" is carried out. This may be used at the border between two countries to reduce the risk of spread from an one area to another. As the EU has no defined borders between countries and the UK has no defined borders between counties ring vaccination is not an option.

It should also be noted that the EU's only policy on foot-and-mouth only is for slaughter. There is no policy for vaccination.

Implications of vaccination

Once a vaccination program is started the disease becomes "endemic", that is the virus would become permanently present in the population. As a consequence it would then infect all cloven-hoofed animals in the country. Vaccinated animals might be protected, however most susceptible wildlife would not have this luxury and the welfare of the wildlife population would suffer as a result.

Vaccination creates foot-and-mouth antibodies in the animal, unfortunately these make it impossible to identify if the animal has had the disease. Given the highly virulent nature of this debilitating disease, and the fact vaccinated animals can not be told apart for previously infected animals many countries will not import animals from "infected" areas.

If Britain were to vaccinate we, and possibly all of Europe, would be classified as an "infected area" being unable to market animals to many parts of the world, including the U.S.A., Canada and the Far East. Britain has some of the best animal genetics in the world, developed over centuries of selected breeding. This, and many other areas of farming industry would disappear over night.

Conclusion

Foot-and-mouth is not a "farming" disease but one that affects all susceptible animals, whether on a farm or roaming the countryside freely as part of our varied wildlife. The disease is hugely debilitating and has significant effects on the welfare of all animals that become infected. To that end control measures must be taken.

Vaccination is not a control option because it is not fully effective or long lasting and is a permanently ongoing process. It is also expensive and would close off the livestock industry to export markets. Such restrictions would have permanent long term effect on the farming industry and UK economy as a whole.

Eradication is the other option, allowing the future animal population to live healthily and provide a sound economic basis for our farming industry.

However, it can be seen the easy with which this disease can enter the country and the speed it has been allowed to spread. Significant changes are needed to the structure of the meat production industry and the movement of animals to help ensure this situation does not arise again.

Final Comment

Food is one of three key elements we need to live, the others being water and air. Some have asked why do we need a farming industry, food can be produced cheaper elsewhere, so why not just import it?

As yourself this. What if there was a World crisis, say a major war or global catastrophe (earthquake, tsunami). As a result food is in short supply or the supply lines are cut. Where would we get the food to feed ourselves? Have we all become so reliant on today's technology and lifestyle that we have become so complacent to believe such an event could never occur. In a crisis we need to be able to feed ourselves. In a crisis farming will become the key industry. Do we really want to take the risk of killing off this potential lifeline?

Additional information on Foot-and-Mouth disease plus up-to-date news on the UK outbreak can be found at www.thePigSite.com