The Heat Is Online

Climate Drives Spread of Sheep Disease

Killer Sheep Disease Heads North as Climate Warms
Reuters News Service, Sept. 9, 2003

MANCHESTER (Reuters) - A killer sheep disease as dangerous as foot-and-mouth but previously confined to Africa has jumped into Europe and is heading steadily north as the climate warms, a scientist said on Tuesday.

Bluetongue disease, which is carried by midges, weakens blood vessels causing heavy hemorrhaging and blindness, making it hard for the sheep to feed, see or move.

"Sheep that can't eat, see or walk very well do however die very well," Philip Mellor of the Institute of Animal Health told reporters at the annual meeting of the British Association for the Advancement of Science.

He said the disease, spread by the Culicoides imicola biting midge, had caused the death of more than half a million sheep since it crossed the Mediterranean into southern Europe eight years ago and was galloping northwards.

Not only was the midge now being found in areas where it had never previously lived, it had now overlapped with other species of midge whose natural habitat was even further north, speeding the spread of the disease into colder climes.

"This is almost certainly caused by climate change," Mellor said, adding that with every one degree rise in temperature, the midge expanded its range 90 km further north.

He said bluetongue -- named because of the hemorrhaging in the animals' mouths -- killed up to 70 percent of infected flocks.

While sheep in continental Europe which had survived infection were now immune, within five years they would either be dead or have had lambs and the new generation would not be.

In Britain, where millions of cattle and sheep were slaughtered two years ago as foot-and-mouth devastated the countryside, all sheep were at risk, Mellor said.

The good news was that there was no animal to animal infection.

But the bad news was that cattle could harbor the bluetongue virus without showing any symptoms and act as a disease timebomb waiting for a midge to come along and start the sheep reinfection process all over again.

Vaccination did help, but current vaccines were live and conversely could actually spark off an epidemic. Because cattle could harbor the disease they too would have to be included in any vaccination program, Mellor said.

However, he said scientists were hard at work to find a safer vaccine which he hoped would be ready within five years.