Facts about Poxvirus / Squirrelpox
http://www.grey-squirrel.org.uk/poxvirus.php
Red Squirrels have had a history of large population fluctuations due
to lots of factors, but a major one is disease. The UK has proved a
difficult habitat for Red Squirrels. Culling because they were
regarded as pests almost made them extinct, with numbers only coming
back because of Red Squirrels introduced from other countries. Their
habitat has also been depleted by humans as forestry practices have
changed. All of these factors are a source of stress to Red Squirrels,
and stressed animals tend to be thinner and weaker than those in good
habitat. Without disease, this might not be too much of an issue, but
when Red Squirrels get infected, their weakened bodies can't cope and
they will often die.
Key points at a glance
1. Red Squirrel population weakened by poor habitat and culling in the
past
2. Poxvirus (Squirrelpox) is just one of the diseases the weakened
population has been susceptible to
3. Their population has fluctuated greatly in the past, almost dying
out at times, which shows they struggle to survive in the UK habitat
4. Weakened Red Squirrels die before they build up immunity to the
disease
5. They need good habitat so they are stronger and healthier to fight
disease
Poxvirus (or Squirrelpox as it is often called) is by no means the
only disease which can kill Red Squirrels. They have also died from
Coccidiosis and more recently Enteric Adenovirus is thought to have
been a cause of at least one confirmed Red Squirrel death. Poxvirus is
the most common disease at the moment, and displays symptoms not
unlike myxomatosis in rabbits. At first the squirrel will seem
lethargic and probably display poor coordination. As the disease takes
hold, lesions will appear around the eyes, mouth, feet and genitals.
It is a common mistake that Grey Squirrels are responsible for
Poxvirus. Research has shown that Red Squirrels were dying of a
disease between 1900 and 1920. Descriptions of the disease give very
similar clinical signs to the disease that scientists now know to be
poxvirus. Most of the Red Squirrels re****ted to be dying had never had
any contact with Grey Squirrels. We'd only spread across 4 out of 40
districts while Red Squirrels were fairly common across the country.
Why don't Grey Squirrels catch Poxvirus?
The answer is that Grey Squirrels do catch Poxvirus. However, having a
habitat more suitable to us, and being physically larger with better
fat reserves, we are more able to survive the disease.
Why don't Red Squirrels have immunity to Poxvirus?
Red Squirrels are living right on the edge of their natural habitat,
which extends from the UK all the way to the far east. The UK habitat
isn't all that suitable, and is getting less and less suitable as
humans alter the forest landscape significantly. So they tend to be
struggling constantly just to survive, and when they catch Poxvirus,
they usually die before their immune systems can build up immunity to
the disease. It is entirely possible for them to survive the disease.
There is one confirmed case where a Red Squirrel in captivity, which
had a good supply of food and shelter, managed to fight the disease,
and was shown to have antibodies which would help protect it from
Poxvirus in future.
If large numbers of Red Squirrels are to fight this disease
themselves, they need good habitat, with plenty of food and shelter,
so emphasis on planting more coniferous forests is im****tant. The
development of a vaccine which could be given to live-trapped red
squirrels before they are released again could be a way in which
humans could also help the reds further.
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