British livestock hit by bluetongue disease
12 October 2007
British government veterinary officers declared September 28 an outbreak of the animal disease bluetongue. This was the first occurrence of the viral disease in Britain.
Carried by midges, the virus affects sheep, cattle, goats and other ruminants.
Symptoms of the disease include fever, high temperature and swelling of the head and neck. Sheep are most affected by the strain of the virus in the British outbreak, which kills 70 percent of those affected. Cows, whilst incubating the disease, may not show symptoms and so can act as a reservoir for the disease.
The outbreak has been a further blow to the Labour government and Prime Minister Gordon Brown, desperate to show it can deal with a series of crises including an outbreak of foot and mouth disease that continues to affect parts of the country.
Unlike the foot and mouth outbreaks, culling of affected animals is not an option in controlling the spread of the disease. It is only spread by midges and is not contagious—i.e., one animal cannot catch it directly from another.
Since it was first discovered, there are now more than 20 cases of the disease, with clusters around Ipswich and Lowestoft and one in the bordering county of Essex. A 20-kilometre control zone has been established around the outbreaks. It is likely that the midges arrived in eastern Britain from the Low Countries across the North Sea, carried by winds in late August.
Bluetongue was once considered a disease of the tropics and sub-tropics. It is endemic in many parts of Africa and was first described in South Africa in 1876. Outbreaks of the disease in the 1950s in the Middle East, Far East, China and Australia were thought to have originated from infected imported meat. In 1998, the virus began to enter southern Europe across the Mediterranean from Africa. It became endemic in Balkan countries, Greece, Portugal, Spain and southern France.
In 2006, the disease began to appear in northern countries affecting Germany, Holland, Belgium and Northern France. More than 3,000 cases of the disease have been reported since its appearance in northern Europe.
As in the case of foot and mouth, it seems that the British government has been complacent and ill-prepared for the outbreak. Just over a year ago, the government chief veterinary officer, Debbie Reynolds, speaking on radio in response to reports of bluetongue outbreaks in Holland, said, “There is an increased likelihood of the sheep disease being introduced by midges, but we think the risk is low overall because this is associated by windborne spread.” It took until summer this year before government scientists warned farmers to watch out for the possible arrival of the disease.
The most effective weapon against the disease would appear to be the use of vaccination. Professor Peter Mertens, a government scientist who has worked on the bluetongue virus for 25 years, told the Independent, “If we vaccinate animals in East Anglia in time to create a buffer zone of animals before the midges start to reappear next May, we may be able to contain the virus or even stop it from re-emerging.”
But the main centre working on the production of a vaccine against the disease is run by the animal pharmaceutical company, Merial, which is based within the government Institute of Animal Health (IAH) in Pirbright, Surrey, in South-East England.
It was laxness in biosecurity at the Pirbright site that was responsible for the recent foot and mouth outbreak. Investigations showed it was the dilapidated state of the drainage system within the IAH compound, coupled with severe lapses of biosecurity that allowed the foot and mouth virus being worked on at the centre to escape and infect nearby farm animals. The current foot and mouth outbreak still continues, with the latest case in the area being confirmed on September 30.
Because of the foot and mouth outbreak and subsequent investigation, Merial has had to suspend work on live viruses. According to the Independent, Merial does not expect to have a viable vaccine until next summer at the earliest. A Merial spokesman said, “We are pretty confident that we have a vaccine that will work. But until DEFRA decides that we can work with live viruses at our Pirbright centre, we cannot make the vaccine.”
There were hopes that cold weather in winter would kill off the midges hosting the virus, but this outcome is now less likely. Last winter in Britain was the second warmest on record, and predictions for this winter are currently for a warm one.
Speaking to the Farmers Guardian newspaper, Nick Taylor, a Reading University veterinary epidemiologist, warned that the midges might survive over winter. He said: “In Northern Europe, bluetongue has spread remorselessly.... Early hopes that the disease would not be maintained over winter did not materialise...the worst case scenario for UK, is that the virus becomes established in the native midge population.”
British farmers would not be compensated for animals that die of the disease. It is yet another blow to the livelihood of many small farmers, currently being hit by the restriction on animal movements due to the ongoing foot and mouth outbreak.