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Ancient roots of leprosy

Uncovering the ancient roots of leprosy

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New research conducted at the University of Texas Anderson Cancer Center is finally unearthing some of the ancient mysteries behind leprosy, which has plagued mankind throughout history. The study found that leprosy may be the oldest human-specific infection, with roots that likely stem back at least ten million years.

The term leprosy is derived from either the Indo-European term lap, which means the removal of scales, or the Greek word for scales, lepra.  It is a disease that is known for attacking a patient's skin and nerves. Left untreated, the disease can lead to extensive skin lesions, deformities in the patient's face and extremities, disabilities, and even death.  The earliest possible account of a disease that many scholars believe is leprosy appears in an Egyptian Papyrus document written around 1550 BC, and around 600 BC, Indian writings describe a disease that resembles leprosy. In Europe, leprosy first appeared in the records of ancient Greece after the army of Alexander the Great came back from India and then in Rome in 62 BC, coinciding with the return of Pompeii's troops from Asia Minor.

Throughout its history, leprosy has been feared and misunderstood. For a long time leprosy was thought to be a hereditary disease, a curse, or a punishment from God. Before and even after the discovery of its biological cause, leprosy patients were stigmatized and shunned. People infected were often confined against their will in leper colonies and in Medieval Europe were required to carry a bell to identify their presence, and even walk on a particular side of the road, depending on the direction of the wind.

Research back in 2008, led by MD Anderson pathologist Xiang-Yang Han, a professor in laboratory medicine, resulted in the discovery of a new leprosy-causing species, called Mycobacterium lepromatosis. Before that time, only one species of bacteria, called Mycobacterium leprae, was known to cause leprosy.  More recently, Han's team analysed 20 genes of Mycobacterium lepromatosis and compared them with those of Mycobacterium leprae. They found that, incredibly, the two leprosy bacteria came from a last common ancestor around 10 million years ago.  Their results also indicated that modern humans carried the leprosy bacteria when departing Africa around 100,000 years ago.  By bringing together factors linked with human evolution, host genetic diversity, and host immunity, the study authors were able to unravel the complex picture of leprosy

Their hypothesis that leprosy existed for millions of years offers new insights into disease pathogenesis. For example, the parasitic adaptation of the leprosy bacteria inside hominid-human hosts is similar to a very long hide-and-seek game. In this scenario, the parasite hides by mutating or removing harmful molecules while retaining protective ones. In the end, this leads to evasion from host immunity, a phenomenon commonly seen in leprosy.

Today, there are effective drug treatments for leprosy, but in the past physicians were willing to try all sorts of remedies to cure this terrible disease. At various times blood was considered to be a treatment either as a beverage or as a bath. This practice persisted until at least 1790, when the use of dog blood was mentioned in De Secretis Naturae. Paracelsus recommended the use of lamb's blood and even blood from dead bodies was used. Treatments through history have also included: snake venom, bee stings, frog poison, scorpion stings, scarification with or without the addition of irritants such as arsenic, the use of chaulmoogra oil, and castration. The first effective treatment (promin) became available in the 1940s and has been refined and developed since then.

Featured image: A man with leprosy ringing his bell to warn of his approach. Photo credit: Wikimedia

By April Holloway

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