Squirrel parapoxvirus
Encyclopedia
Squirrel poxvirus is a virus that causes a fatal disease "squirrelpox" in UK red squirrels
. The virus is often carried by grey squirrels from North America
, which rarely die from the disease. Elsewhere in the Red Squirrel's European range, either the grey squirrel does not occur or it lacks the poxvirus hence the disease only occurs in the UK.
to the disease, and the mortality rate for untreated infected squirrels in the wild appears to be 100%; most dying within 4–5 days of being infected.
There has been some more recent anecdotal evidence on resistance to Squirrel pox in the red population including the finding of a healthy red squirrel with antibodies to the virus in Cumbria http://www.blackwell-synergy.com/doi/abs/10.1111/j.1469-1795.2000.tb00107.x. However the mortality rate is still considered severe, and certainly capable of local extinction of red squirrels in areas that succumb to the disease.
acronym for squirrel parapoxvirus is SPPV. The classification of the virus is still under debate, and the recent studies have suggested that it should be grouped into a clade of its own rather than Parapoxvirus.
, and other poxviral infections have been reported in man. However, no cases of transmission to humans are known.
UK grey squirrels carry the virus but are unaffected by it whereas in red squirrels, the virus causes skin ulcers, lesion
s, and scab
s. It can also cause swelling and discharge (from the lesions/scabs) near the eyes, mouth, feet, and genitalia. Additionally, squirrels that fall victim to the disease often become increasingly lethargic as it progresses. Infected animals are said to resemble rabbit
s with myxomatosis
, in that they are sometimes found shivering and lethargic.
in the north to North Carolina
in the south. The origins of squirrel poxvirus in the UK are mostly unknown. The first confirmed incident was in East Anglia
in the 1980s. It has since spread to Lancashire
(confirmed in 1995-1996), Cumbria
(spring 1998), Durham
(1999), and Northumberland
(1999). The squirrel poxvirus is regarded as a significant factor in the decline of red squirrel populations in the UK
.
Although the squirrel poxvirus has only been recorded once in Scotland
, it may be more prevalent due to lack of thorough testing.
It is thought to be similar to a case of disease seen in East Anglian red squirrels at the turn of the 20th Century.
, there are now only about 140,000.http://www.publications.parliament.uk/pa/ld200506/ldhansrd/vo060201/text/60201w03.htm Most of these are in Scotland
. The decline of red squirrels is blamed mostly on disease, the loss of woodland
s, and competition by grey squirrels. There are over 2.5 million grey squirrels in the British Isles. Red squirrels' survival chances in conifer woods are much higher than in deciduous
woods.
Red Squirrel
The red squirrel or Eurasian red squirrel is a species of tree squirrel in the genus Sciurus common throughout Eurasia...
. The virus is often carried by grey squirrels from North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, which rarely die from the disease. Elsewhere in the Red Squirrel's European range, either the grey squirrel does not occur or it lacks the poxvirus hence the disease only occurs in the UK.
Overview
Grey squirrels very rarely die from this disease as their population has developed immunity having been exposed to the virus for many years; however, they are still carriers of the infection and can spread the disease to red squirrels. In sharp contrast, there are no known red squirrels that have developed immunityImmunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...
to the disease, and the mortality rate for untreated infected squirrels in the wild appears to be 100%; most dying within 4–5 days of being infected.
There has been some more recent anecdotal evidence on resistance to Squirrel pox in the red population including the finding of a healthy red squirrel with antibodies to the virus in Cumbria http://www.blackwell-synergy.com/doi/abs/10.1111/j.1469-1795.2000.tb00107.x. However the mortality rate is still considered severe, and certainly capable of local extinction of red squirrels in areas that succumb to the disease.
Taxonomy
The official ICTVInternational Committee on Taxonomy of Viruses
The International Committee on Taxonomy of Viruses is a committee which authorizes and organizes the taxonomic classification of viruses. They have developed a universal taxonomic scheme for viruses and aim to describe all the viruses of living organisms. Members of the committee are considered to...
acronym for squirrel parapoxvirus is SPPV. The classification of the virus is still under debate, and the recent studies have suggested that it should be grouped into a clade of its own rather than Parapoxvirus.
Transmission
The virus can spread through contact with the infected lesions or contaminated crusts, and can also be carried by mosquitoes. Most poxviruses are highly resistant to drying, which allows crusts to remain infectious for long periods of time. It is believed that the virus can be transferred by contaminated feeders, which is why red squirrel preservation organizations often recommend that feeders are disinfected daily. Many poxviruses are potentially zoonoticZoonosis
A zoonosis or zoonoseis any infectious disease that can be transmitted from non-human animals to humans or from humans to non-human animals . In a study of 1415 pathogens known to affect humans, 61% were zoonotic...
, and other poxviral infections have been reported in man. However, no cases of transmission to humans are known.
Symptoms
UK squirrelpox virus is an entirely different virus to that which causes skin fibromas (tumours) in American grey squirrels.UK grey squirrels carry the virus but are unaffected by it whereas in red squirrels, the virus causes skin ulcers, lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...
s, and scab
Scab
Scab can refer to the following:* Scab, a hard coating on the skin formed during the wound healing reconstruction phase* Derogatory term for a strikebreaker, a person who works despite strike action or against the will of other employees...
s. It can also cause swelling and discharge (from the lesions/scabs) near the eyes, mouth, feet, and genitalia. Additionally, squirrels that fall victim to the disease often become increasingly lethargic as it progresses. Infected animals are said to resemble rabbit
Rabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
s with myxomatosis
Myxomatosis
Myxomatosis is a disease that affects rabbits and is caused by the Myxoma virus. It was first observed in Uruguay in laboratory rabbits in the late 19th century. It was introduced into Australia in 1950 in an attempt to control the rabbit population...
, in that they are sometimes found shivering and lethargic.
Origins
SPPV is found in the eastern part of North America from OntarioOntario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
in the north to North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
in the south. The origins of squirrel poxvirus in the UK are mostly unknown. The first confirmed incident was in East Anglia
East Anglia
East Anglia is a traditional name for a region of eastern England, named after an ancient Anglo-Saxon kingdom, the Kingdom of the East Angles. The Angles took their name from their homeland Angeln, in northern Germany. East Anglia initially consisted of Norfolk and Suffolk, but upon the marriage of...
in the 1980s. It has since spread to Lancashire
Lancashire
Lancashire is a non-metropolitan county of historic origin in the North West of England. It takes its name from the city of Lancaster, and is sometimes known as the County of Lancaster. Although Lancaster is still considered to be the county town, Lancashire County Council is based in Preston...
(confirmed in 1995-1996), Cumbria
Cumbria
Cumbria , is a non-metropolitan county in North West England. The county and Cumbria County Council, its local authority, came into existence in 1974 after the passage of the Local Government Act 1972. Cumbria's largest settlement and county town is Carlisle. It consists of six districts, and in...
(spring 1998), Durham
Durham
Durham is a city in north east England. It is within the County Durham local government district, and is the county town of the larger ceremonial county...
(1999), and Northumberland
Northumberland
Northumberland is the northernmost ceremonial county and a unitary district in North East England. For Eurostat purposes Northumberland is a NUTS 3 region and is one of three boroughs or unitary districts that comprise the "Northumberland and Tyne and Wear" NUTS 2 region...
(1999). The squirrel poxvirus is regarded as a significant factor in the decline of red squirrel populations in the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
.
Although the squirrel poxvirus has only been recorded once in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, it may be more prevalent due to lack of thorough testing.
It is thought to be similar to a case of disease seen in East Anglian red squirrels at the turn of the 20th Century.
Long-term effects
Although red squirrels were once prevalent throughout the British IslesBritish Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
, there are now only about 140,000.http://www.publications.parliament.uk/pa/ld200506/ldhansrd/vo060201/text/60201w03.htm Most of these are in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
. The decline of red squirrels is blamed mostly on disease, the loss of woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...
s, and competition by grey squirrels. There are over 2.5 million grey squirrels in the British Isles. Red squirrels' survival chances in conifer woods are much higher than in deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
woods.