Bluetongue, discovered in a cow near Ipswich in Suffolk, is a similar midge-borne disease to African Horse Sickness, both of which have been spreading north for the last 20 years, possibly because of global warming.
The same species of midge can spread both diseases. Infected midges can potentially be blown for more than 100km by the wind and transported long distances in farm vehicles, making containment difficult.
Britain's first Bluetongue case is not yet considered an outbreak until such time as there is evidence the disease is circulating. Other animals on the farm in Suffolk would be tested for evidence of the virus, officials said.
Further cases would clearly show the virus is circulating in the midge population and a restricted zone put in place.
Bluetongue, or catarrhal fever, can only spread by insect, and affects mainly sheep. It can, however, infect cattle, goats, buffalo, deer, dromedaries and antelope.
It has been a growing on mainland Europe, prompting a prediction earlier in 2007 - now proved correct - that Bluetongue could reach Britain this year.
The case of Bluetongue follows on the heels of a foot-and-mouth outbreak in Britain.
Australia's New South Wales and Queensland are also viral battlegrounds, with equine influenza now affecting an estimated 15,000 horses.
Britain's Horse Trust - the oldest horse charity in Britain - launched a campaign this year for the government to put plans in place for what it said was the eventual arrival of African Horse Sickness.
The trust said its appearance in Britain could spell the death knell for horse racing and all other forms of equestrian sport.
Climate change has been allowing the disease, which can kill 90 per cent of the horses it infects, to spread ever closer to Britain.
British and European horse populations are considered highly vulnerable to the lethal disease.
The pointed to Bluetongue cases on mainland Europe and predicted the disease could breach Britain this year.
The Trust has called on the British Government to:
"African Horse Sickness is related to Bluetongue and is spread by the same midge (Culicoides species). It can kill up to 90% of the horses it infects."
The Trust acknowledges that horses are a low priority for the Department of the Environment, Food and Rural Affairs, which would be responsible for managing and controlling any outbreak.
Because of this, The Horse Trust will spearhead:
Research institutes and vaccine manufacturers are already working to develop more effective and safe cattle and sheep vaccines for Bluetongue.
African Horse Sickness was diagnosed in Spain in 1987-90 and in Portugal in 1989, but was eradicated using slaughter policies, movement restrictions, vector eradication and vaccination. Were AHS to break out in Europe again, under current vector and climate conditions it is inevitable that it will have a much greater opportunity to establish itself - including in Britain.
Although the disease is notifiable in Britain and Europe, a British slaughter policy is unlikely to be viable once the disease is established in the midge vector population.
The British and European horse population is considered highly vulnerable to the disease, with vaccines that currently exist being either unavailable or unlicensed. Some are unsuitable for use where the disease is not endemic.
• The Ministry of Agriculture and Forestry's biosecurity arm, MAF Biosecurity New Zealand (MAFBNZ) says New Zealand already has measures in place to protect against the introduction of bluetongue, but is nevertheless keeping an eye on the situation in the UK where bluetongue has been detected in a cow.
Bluetongue virus affects ruminants (sheep, goats, cattle) and can cause severe epidemics in sheep. The infection seldom causes disease in other susceptible ruminants, but infected cattle are a carrier of infection for other species. It is named for the characteristic swollen blue tongue that appears in the animal around death.
MAFBNZ's Manager International Coordination Derek Belton says the virus is already widespread in many parts of the world, including Australia where it was detected in the early 1980s. There has never been a case in New Zealand.
"In order for bluetongue to be transmitted it requires both the presence of infected animals and specific species of midge that transmit the virus from beast to beast. The midges which are a vital part of the disease life cycle are not present in New Zealand," says Dr Belton.
The only way blue tongue could establish in New Zealand is through the simultaneous importation of infected live animals or germplasm (semen or embryos) and one of the species of midge essential for the virus to complete its life cycle.
"We import germplasm and a very small number of live sheep and cattle under extremely strict quarantine conditions which include multiple specific barriers to exclude bluetongue virus," Dr Belton says. "We have not imported live sheep or cattle from the UK for well over ten years."
MAFBNZ runs a targeted active surveillance programme for bluetongue, looking for both the midge and antibodies to the virus in cattle. Neither has been detected.
"I am confident this new find in the UK poses no additional risk of bluetongue entry to New Zealand," Dr Belton says.