Saturday, April 14, 2012

Leprosy


Leprosy is an infectious disease that affects the skin, the peripheral nerve, and the mucous membranes of the nose, throat, and eyes. It is caused by the leprosy bacillus, Mycobacterium leprae. Destruction of the peripheral nerves by the bacillus leads to a loss of sensation, which, together with progressive tissue degeneration, may result in the extremities' becoming deformed and eroded. In almost all cultures throughout history, leprosy has aroused dread and loathing about the prospect of incurable disease and a lifetime of progressive disfigurement. At one time “lepers,” as those with the disease were long called, were ostracized as unclean and were gathered into isolated “leper colonies” in order to keep them out of sight, to control their contagiousness, and to offer them what little treatment was available. In reality, the leprosy bacillus is not highly infectious, in most cases passing from one person to another only after prolonged and close contact (as, for instance, among family members). In addition, thanks to modern therapy with a number of effective drugs, the disease is now entirely curable, and the term leper, connoting somebody who has had and always will have the disease, thus no longer has meaning and in fact is considered to be offensive because of the social stigma long associated with the disease. Health care officials today do not consider a cured former leprosy patient to be any more “leprous” than a cured former cancer patient is “cancerous.”Despite modern therapy, leprosy is still a persistent disease in many parts of the world, and in many cases the disfigurement and disability caused by the infection cannot be reversed. Millions of people alive today either have or have had leprosy, and more than 500,000 currently require drug treatment. Some 600,000 new cases arise every year. The disease has almost disappeared from most temperate countries, but it is still common in Asia, Africa, Central and South America, and the Pacific Islands. India has the largest number of cases, with more than 60 percent of the world's infected persons. The route of transmission of leprosy remained a matter of debate. The prevailing opinion for many years was that the illness spread via prolonged skin-to-skin contact. Then the theory of respiratory transmission became popular; it posited that the bacillus entered the human body through the lining of the nose. For a time scientists even entertained the possibility of transmission by insect bites. In the late 20th century, experiments with a mouse model of the disease showed that transmission is indeed possible through the intact lining of the nose and through breaks in the skin but not via the mouth, lungs, or digestive tract or through unbroken skin. And, although leprosy can be produced in mice by exposing them to the bacillus, the disease cannot be transmitted from an infected to an uninfected mouse. The current treatment of leprosy is extremely effective, halting the progress of the disease. The bacilli can be killed rapidly and multidrug therapy the use of two or more antileprosy drugs in combination prevents the development of drug-resistant strains. Indeed, multidrug therapy a practice widely adopted in the treatment of tuberculosis and AIDS was first proposed after scientists observed that some cases of leprosy were becoming resistant to sulfones, the earliest class of antileprosy drugs. A multidrug regimen developed by the World Health Organization (WHO) is the current standard of treatment. For patients with localized forms of leprosy and relatively few leprosy bacilli in their bodies, two drugs, dapsone and rifampicin, are given for a total of six months. For patients with more widespread disease and relatively large numbers of bacilli, three drugs dapsone, clofazimine, and rifampicin are given for 24 months. Most patients are able to tolerate the drugs well, but a few experience undesirable side effects or even exacerbations of the symptoms. Relapses, in general, are rare, occurring in less than 1 per 1,000 treated patients.


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