Vikings carried the flesh-rotting disease leprosy to Ireland when they invaded in the 10th century, scientists have discovered. 

Very little is known about how the condition arrived on the Emerald Isle and how lethal it was during the Medieval period.  

Scientists say that the expansion of the Roman empire carried the disease around most of Europe and it was the Scandinavian warriors who brought it to Ireland. 

Five skeletons were found with leprosy across the Emerald Isle, with three in Dublin. 

Analysis of these three bodies revealed two of the individuals were from a colder climate, thought to be Scandinavia, and the other was probably from Britain or north Ireland. 

Vikings carried the flesh-rotting disease leprosy to Ireland in the when they invaded in the 10th century, scientists have discovered. Five cases of leprosy were found in human skeletal remains and chemical analysis was completed on three of the bodies from Dublin. Two of these individuals were from a colder climate, thought to be Scandinavia

Research led by Queen's University Belfast, the University of Surrey and the University of Southampton say the finding adds to a growing body of information about the evolution and spread of leprosy in the past. 

Professor Eileen Murphy, from the school of natural and built environment at Queen's University Belfast said: 'Relatively little is known of leprosy in Medieval Ireland. 

As an island located at the far west of Europe, it has the potential to provide interesting insights about the historical origin of the disease.

'Ireland is of particular interest in the history of leprosy as it was never part of the Roman world nor underwent any significant occupation by later Anglo-Saxon settlers.'  

Five cases of leprosy were found in human skeletal remains excavated from known burial sites. 

Three of the individuals were from a cemetery in Dublin and two came from County Kildare and County Antrim.  

The Dublin skeletons were chemically examined to understand their early life history and where they lived.  

None were found to be local, with one believed to be British or from the north of Ireland.

Vikings tried to rule Ireland for centuries. The Vikings, however did not conquer the island - by the middle of the 10th century they failed to control the territory in Ireland (stock)

Leprosy is a long-term infectious disease which can result in the inflammation of the nerves, respiratory tract, skin, and eyes. In 2012, the number of chronic cases of leprosy was 189,000, down from some 5.2 million in the 1980s, with India accounting for more than half of all cases (stock)

WHEN DID VIKINGS INVADE IRELAND?

In the 10,000 years since Stone Age cavemen first arrived, the Irish have established distinct cultural regions.  

Researchers have recently found 23 distinct genetic clusters, separated by geography by comparing mutations from almost 1,000 Irish genomes with over 6,000 from Britain and mainland Europe.

These are most distinct in western Ireland, but less pronounced in the east, where historical migrations have erased the genetic variations.  

They also detected genes from Europe and calculated the timing of the historical migrations of the Norse-Vikings and the Anglo-Normans to Ireland, yielding dates consistent with historical records. 

The Vikings left their genetic footprint in Ireland when they invaded the island, launching their first attack in 795 AD by raiding an island monastery. By the 840s, the Vikings began to establish permanent ship bases along the coastline

The study paints a new and more complex picture of the genetic landscape of Ireland, and demonstrates the signatures that historical migrations have left on the modern Irish genome. 

The Vikings left their genetic footprint in Ireland when they invaded the island, launching their first attack in 795 AD by raiding an island monastery.

The Vikings continued to stage small-scale attacks on unprotected costal monasteries before sailing to River Shannon in the 830s to steal from inland religious settlements. 

By the 840s, the Vikings began to establish permanent ship bases along the coastline from which they could plunder all year. 

Norse influence in Ireland began to decline by the time of the rise of king Brian Boru (pictured in an imagined depiction)

The Vikings also enslaved some of the Irish people, and were able to raid the land by taking advantage of the fact that Ireland was particularly politically fractured.

The Vikings, however did not conquer the island - by the middle of the 10th century they failed to control the territory in Ireland. 

The fractured political system in Ireland worked in the island's favour - if one ruler was killed, it did not destabilize the entire island. 

Norse influence in Ireland began to decline by the time of the rise of king Brian Boru. 

He sacked the Viking town in Limerick in 968 AD and became the overlord of Cork, Wexford and Waterford. 

In 1014, the king's army routed the Vikings and their allies at the Battle of Clontarf outside Dublin, but a small group of Norseman killed the elderly kind as he was praying in his tent after the battle. 

The Viking remained in Ireland after agreeing to pay a tribute, but the Viking Age in Ireland didn't come to a definitive end until the Norman invasion in the 1170s and the last Norse king of Dublin escaped to the Orkney Islands. 

Source: History.com - Globetrotting Vikings: The raiding of Ireland

The other two skeletons grew up in Scandinavia it found. 

Professor Alistair Pike, archaeological scientist at the University of Southampton, said: 'The key to understanding the origins of these individuals were the oxygen and strontium isotopes in their teeth. 

'These showed that two of the individuals came from an area that was colder and which had older geology than is present in the UK or Ireland, and best matched parts of Scandinavia.' 

Further genetic analysis was done on the leprosy bacterium (M. leprae) strains themselves from two of the Dublin skeletons. 

The strains date back to the early 10th century through to the 13th century and show the lepers were afflicted with two separate strands of the disease. 

One had probable origins in Scandinavia (Type 3), while the other first developed in the Middle East (Type 2). 

Professor Mike Taylor, Bioarchaeological Scientist at the University of Surrey, said: 'As past leprosy strains evolved, the genetic fingerprint of an archaeological case of leprosy can tell us about the possible movements of that individual.

'The two strain types discovered are highly similar to those present in cases in medieval Scandinavia, increasing the likelihood that this is the origin.'  

WHAT IS LEPROSY? 

Leprosy is a long-term infectious disease which can result in the inflammation of the nerves, respiratory tract, skin, and eyes.

The disease is initially symptom-less and can remain undetected for five to 20 years.

Typically found among those living in poverty, leprosy was common during the Middle Ages and then again in nineteenth century but it can still be found in developed and developing countries today.

In 2012, the number of chronic cases of leprosy was 189,000, down from some 5.2 million in the 1980s, with India accounting for more than half of all cases.