Squirrel Pox and other squirrel diseases
The squirrel pox virus, sometimes erroneously referred to as squirrel para-pox, is responsible for the disease known as squirrel pox which presents in red squirrels with a mange, scab or myxomatosis-like symptoms, leading to rapid loss of body condition and subsequently death. The animal’s behaviour may change especially toward the end, they become lethargic and more approachable. The virus appears to be endemic amongst the UK grey squirrel population and its effects, if any, on this species are unclear.
Nearly all grey squirrels with pox antibodies do not display any outward symptoms. Pox-type viruses are fairly resilient and will survive outside the host for a considerable time if the conditions are favourable. Dry weather may mean the virus remains viable for over a month. Wet conditions will reduce its viable period considerably. Outside the host the virus can be killed by good hygiene procedures using anti-viral veterinary disinfectants. Once in a population of squirrels the virus spreads very quickly, isolated woodlands can quickly lose all their red squirrels.
The NISF has developed a Standard Operating Procedure (SOP) document that explains the best procedures for cleaning and disinfecting traps and squirrel feeders.
The photos show a red squirrel that has died of Squirrel pox, the animal has been severely visually impaired by the infection and will not have been able to feed itself once the disease advances, also note sores on the paws.
- Download the Northern Ireland Squirrel Forum Standard Operating Procedure: Squirrel feeding station / trap hygiene (pdf 40Kb)
Despite being blamed, at least in part, for the decline of the red squirrel in England and Wales, Squirrel Pox was not recorded in Ireland until very recently. Squirrel Pox was first discovered in Northern Ireland at Tollymore Forest Park County Down during March 2011 and 3 months later in the Glenarm area of County Antrim. The reason for its sudden discovery in two locations within three months when it was not previously known in Ireland is unclear.
We suspect that it has always been present but the last severe winter may had lead to increased squirrel movements as they were looking for food and or more frequent visits to artificial feeding sites, which in turn lead to more contact between individuals especially as the grey squirrel population has continued to increase.
The exact mode of transfer of the virus between animals is unclear, but it is likely passed on directly from contact with body fluids such as saliva or scent gland secretions. There is also the possibility that parasites such as mites, fleas or ticks play a role in the viruses spread.
There is no known risk to Humans from Squirrel pox but washing your hands after handling any animal is advisable as other pathogens may potentially cause you harm.
- If you see a sick or dead red squirrel contact Squirrels@doeni.gov.uk or phone ( 028) 9056 9551
The picture below shows a red squirrel with the early signs of pox, swelling around the eyes, paws and mucus membranes.
Notably the animal may only be affected down one side of its body, at least initially. 
The NISF has produced some guidance on the symptoms of Squirrel Pox as observed by members of the Tollymore Red Squirrel Group during the first half of 2011. These guidelines can be viewed or downloaded here (pdf 1513Kb).
Ongoing research by Queens University Belfast sponsored by the NIEA is scientifically looking into threat of squirrel pox to Northern Ireland's red squirrels. They will also be looking into levels of virus antibodies being carried by grey and red squirrels across the country. The work hopes to identify the mode of transfer of the virus between squirrels. We are also attempting to establish if theories of localised immunity to squirrel pox among certain groups of red squirrels in Northern Ireland have any grounding.
Red squirrels seem particularly suscepible to a range of other diseases, this is probably due to the fact they are in relatively isolated populations, geographically separated from neighbouring populations, which in turn probably restricts the local genetic diversity. There is certainly a risk that should an infection get into a isolated population that those squirrels can be severely reduced in number and there are not enough new squirrels from satellite populations to back fill the losses. The spread of most of these diseases rely on close contact between animals, therefore where squirrels are attracted to artifical feeding sites there is an increased risk of pathogens coming into contact the visiting animals. Where feeders are used by squirrels frequent disinfection as detailed above can reduce disease spread.