How many leprosy patients have been ostracized from their community since Antiquity? This disease, also known as Hansen’s disease, has indeed always stimulated the imagination and the Bible devotes several chapters to it. It is a chronic infectious disease that causes damage to the peripheral nerves (neither the brain nor the spinal cord), skin, mucous membranes of the airways and eyes. We now have a very effective treatment to treat this once incurable pathology. But if left untreated, it can severely mutilate the skin, and nerve damage leads to muscle atrophy and therefore disability.

In recent decades, the fight against leprosy has seen tremendous results, with its prevalence falling by 90% worldwide. However, it remains a public health problem in several countries, such as India and Brazil. As for France: the disease is still present in Réunion and Guyana where a few isolated cases are notified each year to the health authorities. (1) Mayotte, in the Indian Ocean, is the most affected department: 307 new cases were diagnosed there from 2006 to 2011. This is the only French territory where leprosy is considered endemic, exceeding the threshold of 5 people affected in 10. (000)

Since the bacteria responsible for leprosy multiply very slowly, the incubation of the disease can last several years, from 2 to 10 years, and sometimes even 20 years!

• Leprosy can be recognized by the skin lesions it causes. Painful patches of depigmentation, or reddish, appear and sometimes growths.
• The skin thickens and damage to peripheral nerves causes loss of sensation.
• Leprosy also causes muscle weakness and sometimes paralysis, most often of the hands and feet.
• Eye disorders can cause blindness.

The diagnosis is confirmed by testing for the bacillus on an earlobe smear. Leprosy is said to be “paucibacillary” when the patient presents from one to five insensible skin lesions, and “multibacillary” if he presents more than five.

The infectious agent responsible for leprosy is the bacteria Mycobacterium leprae. It is more precisely a bacillus, therefore a rod-shaped bacterium. Researchers from the Institut Pasteur have demonstrated, thanks to the study of its genome, that a single clone of the bacillus is responsible for the global pandemic. According to this discovery, leprosy would originate in East Africa or the Near East, then would have spread as human migrations proceed. (3)

Humans are the sole reservoir of the disease and leprosy is transmitted from person to person via droplets in the mouth or in the nose. But contrary to popular belief, leprosy is not very contagious and is only transmitted through close and prolonged contact with an infected person. The risk of becoming infected while traveling to an endemic area is therefore low. Important note: a person with leprosy but treated is no longer contagious.

The World Health Organization provides patients with free treatment that is effective, with few side effects, and prevents the transmission of the disease. This is multidrug therapy (MDT) which combines three antibiotics over a period of six to twelve months: dapsone, rifampicin and clofazimine.