Leprosy is a chronic communicable disease which affects particularly the nerves, the skin and mucosae. Damage to, and ultimate destruction of, the nerves leads to the deformities which used to be regarded as typical of the disease. These involved the upper limb (claw-hand, wrist-drop), the lower limb (claw-toes, foot-drop), the eye (anaesthesia of the cornea, paralysis of the eyelids) and ulceration of the larynx; and resulted in neglected cases of extensive ulceration of hands and feet, with loss of digits, hoarseness of voice and severe impairment of vision or total blindness.
Leprosy is caused by a bacterium that takes up to 20 years to display symptoms. The disease is curable, only slightly contagious, and does not always cause deformities. It attacks at any age and either sex, and the effects show the widest possible variation - from complete refractoriness to high susceptibility. Hence leprosy may be a small localized patch in the skin, or a progressive generalized disease affecting the skin of the entire body, all the superficial nerve trunks of limbs and face, and the lining of the nose. In any population, a small proportion succumb to the latter form; most seem to be refractory to infection. Standard treatment requires months of antibiotic drug therapy, and at present only one patient in five is able to get effective treatment.
Because of misunderstanding, ignorance and prejudice, leprosy is often regarded as medically unique, and because of its long incubation period, inauspicious onset, slow and painless development, and slight tendency to shorten life, it is surrounded by an aura of mystery. The deformities and disfigurements, blindness and mutilations habitually associated with leprosy are mainly the result of damage sustained by tissues (muscles and skin) whose nerves have been destroyed as the result of leprosy. It is a major crippling disease, and hence is of economic importance.
The earliest written references to true leprosy are from India (600 BC), whence it was probably introduced into the West (with Alexander the Great's troops, 327-326 BC). Enormous confusion existed in the literature before leprosy was delimited (in 1847) as a specific disease and as caused by a specific micro-organism Mycobacterium leprae (1873). References to 'leprosy' in the Old Testament of the Bible (Authorized Version) are a mistranslation. Leprosy has virtually disappeared from north-west Europe, but still exists in countries of Southern Europe. Imported cases comprise a manageable problem in the industrialized West.
Leprosy occurs in most countries (hot or cold, wet or dry, low-lying or mountainous), but the bulk of the up to 6 million sufferers live in the developing countries. As of 1993, there were 121 countries where leprosy was endemic, with 1.6 billion people being at risk. 80% of all registered leprosy patients live in just five countries (in decreasing order of case numbers) India, Brazil, Nigeria, Myanmar and Indonesia. India has more than two million reported sufferers.
During the early 1990's in the 28 most severely affected countries in Latin America, Africa and Asia, rates of registered cases reached as high as 10 to 30 cases per 10,000. However, the incidence of leprosy has declined dramatically in the 1990's due to multidrug therapy, in which two or three drugs are combined to attack the leprosy bacillus, each in a different way. In 1992, WHO began trials of a cocktail of two powerful antibiotics, ofloxacin and rifampicin, which it believes could reduce treatment duration from four years to four weeks and could wipe out the disease sometime in the next century. In 1986, WHO reported 5.4 million registered patients globally. By 1996, this number had dropped to less than 1 million cases. In 1998 there were 684,000 new cases.
Although the disease is now easily curable, it is suspected that many cases of unregistered, whether for economic reasons or for fear of stigma. As a result, even though it may be "officially" eradicated, many cases may go undetected. With its 10 year incubation period, many cases could emerge long after the relevant health programmes have been terminated. It is predicted that there will be many people, especially in developing countries, suffering from leprosy-related disabilities long beyond the target eradication data of 2000.