Determined resistance to foot-and-mouth vaccination

 

Irish veterinary experts are strongly against the idea of vaccinating livestock against foot-and-mouth disease, despite cases accelerating in Britain. Their opposition is on practicality, disease-free status and cost grounds - and because the disease is not endemic. But they point out that if a policy of containment of the disease in a particular area became a problem, there were stocks of vaccine in the EU which could be used.

Vaccination has been banned in EU countries since the early 1990s, basically for trade reasons, because any country vaccinating cannot export to major markets such as the US, Canada and Japan. Prof Joe Quinn, of UCD's veterinary college, says the proposal is "unrealistic" because foot-and-mouth disease has seven major sero-types and possibly 60 to 70 sub-types or strains. "You would have to have the particular isolate available before vaccination or you would have to anticipate correctly what the next outbreak might bring. When you vaccinate against disease there is a certain planning process involved. For example, the human influenza vaccine of a couple of years ago doesn't protect against the present strain."

He says vaccination provides protection for about six months, possibly up to a year and then not at all - and the protection is only against the particular strain against which the animals are vaccinated. Animals do not become immune until some weeks after vaccination.

"Once you start vaccinating, you have sero-positive animals in the country. If you have an outbreak, you have sero-positive animals which are not easy to distinguish from the field outbreaks. I think we should keep vaccination a long way down the list for Ireland."

A vaccinated cow, for example, which became infected while the immunity was waning could still excrete the virus and develop into a carrier status, which could persist for as long as two years.

He says new vaccines are being developed, but "it's not really the answer. The old problem of range and duration of immunity is disappointing". But having worked in Jordan, where the disease is endemic, Prof Quinn says vaccination is the only way to proceed in those circumstances.

Mr Patrick Rogan, deputy chief veterinary officer with the Department of Agriculture, notes that vaccination against the disease was never carried out in Ireland, Britain or Denmark, although up to the early 1990s, the Netherlands, Germany, Italy and Greece would have used vaccination at different times. "In terms of exposure, it was perceived there were greater risks and a greater likelihood of it occurring in other member-states. Ireland and Denmark, in particular, had a `no vaccination' policy because we had access to the US and Japanese markets."

He says vaccination was used in countries such as Greece in a "limited and highly focused " manner when, for example, there were outbreaks in Turkey. Vaccination was used to create a firebreak to prevent the spread of the disease. In the current situation in Britain, vaccination would protect only against that highly virulent Asiatic strain and not against any other.

He agrees with Prof Quinn on the problem of distinguishing between the antibody reaction in animals and the actual disease as transmitted in the case of outbreaks of the disease. Mr Rogan says the sheer logistics of vaccination are staggering. "Britain has the largest sheep flock in Europe - it used to be 40 million. The British cattle herd used to be of the order of 11 million. At the moment, if we were to start vaccinating here, we have 7.5 million cattle, plus sheep, plus pigs - anywhere up to 15 million animals - and that creates its own dilemmas. "You would have a huge amount of movement of vaccination personnel which can contribute to the spread of the disease itself. Plus, vaccination can lull people into a false sense of security and they stop restricting access and taking precautions."

He says vaccination might be necessary twice a year "at massive cost with questionable value sometimes".

New strains of vaccine are being developed and will allow experts to distinguish between the antibody presence and the real disease, but "to get them from the laboratory stage into field use takes a long time".

Mr Damian McDonald, secretary of the Irish Farmers' Association's animal health committee, says vaccination should be an absolute last resort. "It would be admitting the disease had defeated us. Our disease-free status would be downgraded and our export markets damaged. The cost to the economy would be huge."