Squirrel pox is a fatal disease currently affecting red squirrel populations in some areas. Epidemics of disease caused by an unidentified agent have been
described in Britain since early last century. In the 1970’s Ian Keymer investigated causes of diseased red squirrels in East Anglia and as a result of his work a pox virus was identified in eyelid lesions (Scott, Keymer & Labram, 1981). It is now certain that this pox virus is a significant factor in the decline
of the red squirrel population in the UK.

The origin of squirrel pox virus in red squirrels is the introduced American grey squirrel. Research shows that the antibodies to the virus are very common in many grey squirrel populations in England & Wales (although not in Scotland until recently – 13 grey squirrels have tested positive for antibodies since June 2005) but only one case of disease has been found in a grey squirrel. Red squirrels are not found to carry the antibodies unless they are already
succumbing to squirrel pox disease. It is therefore thought that grey squirrels act as a reservoir host for the virus. All wild-living red squirrels observed to be
affected by squirrel pox virus appear to die within 2 weeks of becoming infected.

As yet we do not know the route of transmission. Possibilities include transfer via saliva or scent marking secretions at feeding or scent-marking sites, or perhaps by ectoparasites (fleas, lice, ticks and mites) which may transfer from animal to animal in the dreys. The virus is unlikely to spread through the air if it behaves like other pox viruses. Further research in this area is needed.

Visible symptoms of squirrels with squirrel pox include wet, discharging lesions or scabs around the eyes, ears, mouth, feet and genitalia: squirrels generally become increasingly lethargic as the disease progresses, chiefly due to inability to feed properly.

Photo - Corrie Bruemmer