Although the Isle of Man is not home to native squirrels, the ‘red versus grey’ debate is sometimes raised as an island issue with some animal activists campaigning for the island to become a sanctuary for the red squirrel.

Grey squirrels carry a disease (the squirrelpox virus) that is fatal to their red cousins, and they can eat a wider range of seeds and nuts, which gives them a ‘survival of the fittest’ ecological advantage.

The problem is, of course, a man-made one because the Victorians introduced grey squirrels as a novelty species in the 1870s; whereas the reds are estimated to have been around for about 10,000 years and are classed as indigenous in the UK.

The number of greys is thought to exceed three million, compared with only about 160,000 reds – including the one pictured who lives in Formby on Merseyside.

Formby is famous for its pinewoods and spruce trees - the red squirrels’ preferred habitat, but less favoured by greys.

The grey squirrel has, to-date, received all the bad press and some people see it as a legitimate species for culling, but the red squirrel has just hit the headlines with a new development: scientists from Leicester University have discovered that red squirrels were the most likely source of leprosy in humans in medieval times.

Some 1,000-year-old archaeological finds from Winchester have shown similar leprosy strains in both human and squirrel remains.

Whether squirrels gave the disease to humans or the other way round is not known, but scientists believe that whatever its origin it is likely that leprosy was being passed zoonotically (i.e. to/from animal to human).

Before this research was undertaken there was no consideration for the role that animals might have played in the transmission and spread of leprosy.

In ancient times Winchester was well-known for its leprosarium, a hospital for people with leprosy, and for its connections to the fur trade. In the Middle Ages squirrel fur was widely used to trim and line garments, and many people also kept squirrels as pets.

In the wake of Covid-19, zoonotic diseases and their origins are becoming more of a focus for research, in an attempt to understand their appearance and persistence. But the leprosy scenario is not the earliest known case of animals infecting humans (or the other way round) – it is preceded by tuberculosis (TB).

Humans are thought to have acquired TB from cattle during the Neolithic period, around 10,000 years ago, when people first took up farming.

Other examples include the Black Death, around 1350, which originated in marmots in Asia and was then transmitted through infected flea bites; and in 1918 Spanish flu, which originated in poultry, killed more than 50 million people around the world.

Back to leprosy, the last case in humans in the UK was recorded in 1798 (although it is still prevalent to this day in parts of Asia, Africa and South America), but it is still found in red squirrels.

While transmission to humans is feasible it is extremely unlikely because people simply don’t have prolonged contact with squirrels anymore.

The red squirrel’s links to an ancient disease will not impact on its status as a ‘priority species’ in need of urgent conservation action in the UK.

But the debate still goes on about whether they should be introduced in the Isle of Man.

The prevailing opinion seems to be that they have never been indigenous in the island and so they would be classed as a non-native invasive species.

As such, they could have a detrimental effect on the island’s ecosystem, eating bird eggs for example; plus there may not be a sufficient quantity of their principle diet of seeds and nuts, which could lead to starvation.

Let’s hope that populations in places like Formby are able to survive and thrive, so that the red can hold its own against its grey cousins.