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Foot and mouth disease returns to the UK

August 6, 2007 By Daniel Cressey This article courtesy of Nature News.

Laboratories under the spotlight as disease found on farm.

Foot and mouth disease has once again appeared in the United Kingdom, a country whose farming industry was devastated by an outbreak in 2001. On Friday 3 July, the country's Department for Environment, Food and Rural Affairs (Defra) confirmed it had identified the disease virus in cows on a farm in Surrey. The virus is already suspected to have come from one of two nearby laboratories working on the disease and its vaccine.

Why is foot and mouth so bad?

Foot and mouth is highly contagious and sometimes fatal to animals, especially young ones. It is very rare for the disease to pass to humans, nevertheless the potentially devastating impact on farmers due to restrictions on animal movements around and out of the country means it is widely feared.

The disease is a particularly sensitive issue in the UK where over six million animals were culled in a previous outbreak in 2001. Research shortly after the outbreak claimed that more rigorous control measures could have reduced the number of animals culled by up to 60% (see 'Slack cull killed more').

Why are laboratories being blamed?

Defra says "present indications" are that the strain involved in this outbreak is similar to one called 01 BFS67. This strain was isolated 40 years ago in the 1967 outbreak, but it is used at two laboratories at Pirbright, about four miles from the affected farm.

"We're not completely sure yet, but it looks like it is a laboratory release," says Professor Neil Ferguson, a modeller of disease spread, based at Imperial College London.

The Institute of Animal Health site at Pirbright uses this virus as a reference strain for its research on foot and mouth disease. Merial, an animal health company, which also has a site at Pirbright, used the strain in mid-July to make a batch of foot and mouth vaccine. The presence of laboratories using this unusual strain so close to the infection site has led many to conclude the virus came from them. Recent floods are also being investigated as a possible route for the virus's spread.

What biosecurity is in place at these laboratories?

Some experts have expressed surprise that the virus might have leaked from the Pirbright facility. Facilities such as these are required to have air-locks, changing rooms and showers for staff, and the laboratories are kept at negative pressure. This means the laboratory is kept at a lower pressure than its surroundings, ensuring air does not escape the building before it can be filtered.

"This was a Defra category four [laboratory] which is one below the sort of labs that deal with smallpox and Ebola," says Ferguson. "A Defra category four should be at a level which is just below that which is suitable for dealing with a [category four] human pathogen."

What happens now?

Defra has already culled animals on the infected farm. It has also put in place restriction zones around the farm and is tracing and culling potential 'dangerous contacts', where other animals or premises have a very high risk of exposure to the disease.

So far it has identified one such contact and culled the animals in question. This morning, the UK government emergency committee dealing with the response to the outbreak heard that there had been no new cases in the past 24 hours.

A general movement ban on susceptible animals is also in place across the United Kingdom. This includes not only normal farm animals such as cows and sheep, but also llamas, deer and zoo animals including elephants.

Investigations have been started by Defra; the UK Health and Safety Executive is also investigating Merial, and the Institute for Animal Health. An independent review into biosecurity arrangements at both sites has also been commissioned. This will be led by infectious disease expert Brian Spratt of Imperial College London.

If the disease spreads, vaccination or wider culls may be used to contain it.

To vaccinate or not to vaccinate?

There is much controversy over whether vaccination is a good way of dealing with foot and mouth outbreaks. A major stumbling block has been the absence of a reliable way to differentiate between animals with the disease, and those who have been vaccinated against the disease.

In 2003, researchers at the Federal Research Centre for Virus Diseases of Animals in Tübingen, Germany, claimed to have a new fast laboratory test that could differentiate between the two and would make vaccination viable (see 'Test tells apart infected and vaccinated foot-and-mouth cattle'). Experts warn, however, that even a 99.9% reliable test will misdiagnose many animals in a major outbreak.

But there are other problems. There are several types of the virus and not all vaccines will protect against all of them. Additionally, vaccines also take time to provide immunity, which could still allow an outbreak time to spread.


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