October 15, 2008
Red Squirrel Could Become Immune To Deadly Disease
Scientists in the UK have discovered that some red squirrels have developed immunity to a disease that has posed a threat to the endangered animals.
Introduced to the UK from North America in the late 19th Century, grey squirrels are known to spread the pox, and while it has no affect on them, red squirrels who are exposed to the disease will die within weeks.
But a new study published in EcoHealth found that a vaccine could bring hope to red squirrels.
As the grey squirrels increased their range, red squirrels have suffered huge population declines and now exist in just a few pockets around the British Isles.
An estimated 211,000 red squirrels remain in the UK, compared with more than 2.7 million greys.
While scientists believe the larger and more aggressive grey squirrels have been able to out-compete their red cousins for resources, they believe that a deadly pox that appeared soon after the greys arrived has also been responsible for the catastrophic decline.
"Squirrel pox is almost always fatal in red squirrels," said lead author Tony Sainsbury, from the Institute of Zoology, Zoological Society of London.
"We are not sure exactly how it kills them - we think it must have some sort of effect on the heart or another vital organ because it can kill them very quickly."
He said the pox have caused red squirrel populations to drop 25 times faster than normal.
David Stapleford, a red squirrel breeder at Pensthorpe Nature Reserve, Norfolk said: "The pox annihilates the red."
However, the new study shows that reds may be making a comeback.
Sainsbury and his colleagues analyzed fluid samples taken from 500 squirrels that had been brought to the Institute of Zoology for autopsies between 1993 and 2005 to investigate how the pox was spreading.
"Up to now, we have never found antibodies to the virus in the red squirrels," Sainsbury said.
"So it appeared that whenever red squirrels were exposed to the virus, they were getting the disease and dying."
"But when we looked at these samples, we found there were eight squirrels that had antibodies to the virus. They must have been exposed at some point to the virus, and either didn't develop the disease or developed the disease and managed to fight it."
This marked the first evidence that red squirrels may be able to become immune to the disease.
The team is now planning to look at how widespread this immunity might be and to investigate why and how the red squirrels have been able to develop this ability to resist the pox.
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