Adenovirus threat to British red squirrels

Mammal Society and Red Squirrels Trust Wales, Press Release 

Adenovirus threat to British red squirrels

mammal society

Research published in The Mammal Society’s scientific journal, Mammal Review today, Tuesday 9th Sept, reveals adenovirus as a growing threat to the conservation of DECLINING native red squirrels.

The virus can produce lesions in the digestive system with diarrhoea and intestinal bleeding. Disease is however difficult to detect because the characteristic lesions in the intestines decay rapidly after an animal dies and may no longer be visible to an examining veterinary pathologist. Through the use of laboratory tests including screening for viral DNA, it is now known that the virus is associated with significant mortality in red squirrel captive breeding programmes throughout the UK. More than 80% of captive red squirrels screened were found to have the infection.

Researchers also discovered that wild and captive red squirrels can be infected but without developing disease. On Anglesey, otherwise healthy squirrels that were killed by road traffic or other traumatic injury were found to be infected.

To investigate whether adenovirus was found in other woodland rodents, grey squirrels and wood mice were screened. It has been long known that grey squirrels spread squirrel pox virus to native red squirrels and scientists have now discovered that up to 54% of grey squirrels can be infected with adenovirus. It remains unclear whether the virus causes disease in grey squirrels or if they are involved in transmission to red squirrels. The discovery of infected red squirrels on the Isle of Wight, where grey squirrels are absent, reveals red squirrel infection can be found in areas without grey squirrels. However, wood mice are present here, and this species is also found to carry adenovirus.

Researchers are now focusing upon the role that wood mice may play in the spread of adenovirus and on ways that red squirrel conservation programmes can limit the impact of adenovirus.

Dr Craig Shuttleworth of Red Squirrels Trust Wales said, ‘adenovirus poses a significant risk to red squirrels where rodents come into close contact with one another, such as at garden bird tables, forest supplemental feeding stations, or in captive breeding settings. The availability of foods at bird tables and feeding stations often attracts a range of other species including wood mice and it would be prudent to try and limit mouse activity.’

‘The situation is further complicated because blood tests do not always reveal the presence of infection in living red squirrels and where infection produces illness, sick squirrels don’t show any obvious external signs and often die unseen in nests and are not discovered.”

The Mammal Review paper provides a series of recommendations on trap and squirrel feeder disinfection, and reducing contact between rodent species at feeders or bird tables. It also highlights future research into adenovirus infection including identification of any variation in viral strains found in different mammal species.


1 The Mammal Society: The Mammal Society is a charity advocating science-led mammal conservation, leading efforts to collect and share information on mammals, encourage research to learn more about their ecology and distribution, and contribute meaningfully to efforts to conserve them.

2. Mammal Review: Mammal Review is The Mammal Society’s quarterly international scientific journal of mammal research and review studies, covering all aspects of mammalian biology and ecology. It is owned and published by Wiley with Volume 44 Issue 3 available here.

3. Red Squirrels Trust Wales: A dynamic partnership between landowners, community groups and local volunteers working to improve woodland habitats, erect nest boxes, provide supplemental feeding and monitor populations.

For a more detailed conversation of the adenovirus threat to British red squirrels contact Dr Craig Shuttleworth of Red Squirrels Trust Wales

on:  07966150847 or 01248 601042

If you can’t contact Dr Shuttleworth please call Marina Pacheco at The Mammal Society on: 07726206460