Featured Infectious Disease: Leprosy
In the United States, a federal hospital for leprosy sufferers is being phased out and its last 69 residents are being encouraged to leave the facility. And the World Health Organization targeted the year 2000 for eliminating leprosy on a global basis. Leprosy, that age-old scourge of humankind, finally may be on the run. Here are facts about this infectious disease.
What is leprosy?
Leprosy, also called Hansen's disease, is a mildly infectious disease that attacks peripheral nerves. It is caused by a bacillus, Mycobacterium leprae. In very serious cases, the bacilli may be found in the lymph nodes, male testes, spleen, liver, and bone marrow. The infection can damage nerves in the face and body, leading to a loss of sensation and paralysis. Because sensation is lost, everyday activities are fraught with danger as wounds go unnoticed. Even stones in shoes and grit in the eyes may lead to serious harm when left unattended. Patients may lose fingers, feet, and eyesight.
When did it start?
One of the oldest-known pathogens to afflict humans, leprosy may go back as far as 600 B.C. The ancient Greeks and Romans learned painful lessons about leprosy after their armies returned victorious from Asiaunwittingly bringing back the previously unknown affliction with their plunder. In the Middle Ages, sufferers had to wear special clothing, ring bells to warn others that they were close, and walk on a particular side of the road, depending on the direction of the wind.
Dr. Armauer Hansen first discovered the leprosy bacillus in Norway in 1873. He is credited with identifying one of the first bacteria known to be a human pathogen. Today, leprosy is often called Hansen's disease.
Who gets the disease?
Anyone can get the disease, although most people have a natural immunity to leprosy that makes it perhaps one of the least contagious of all infectious diseases. A small percentage of people get the disease, and children seem more susceptible than adults. Every hour, 65 new cases of leprosy are detected; 11 of these affect children. Leprosy is relatively rare in the United States, where 200 new cases are detected every year and 6,000 people have the disease. But this insidious illness, which now flourishes mainly in poor countries, may not be easy to eradicate. Worldwide, about 700,000 new cases were detected in 1997, and three countriesIndia, Indonesia, and Myanmaraccount for 70 percent of the new cases reported from around the world every year.
In Africa, leprosy remains a significant problem. Eradication has proven difficult because the rise of AIDS and resurgence of major tropical diseases have strained already scarce resources. Social unrest and armed conflict have also weakened health services. In Latin America, leprosy remains a perennial problem, with Brazil accounting for 80 percent of cases. Sporadic cases also occur in Central and Eastern Europe, where underreporting remains an issue.
How does it spread?
It is a bit unclear exactly how leprosy spreads. In a single sneeze, an i
nfected person can launch 100 million bacilli. The organism can remain potent even when dried out, taking the opportunity to infect someone through the nose or a break in the skin.
Once inside the body, the germ heads for cooler places, particularly the skin, nerves near the surface, and the testicles. Highly susceptible patients are likely to show large numbers of bacilli in their nose, ear lobes, face, buttocks, and larynx. Patients with lepromatous leprosy, the more serious form of the disease, may have a nauseating stench arising from the billions of dead leprosy bacilli that may be exuded from the skin.
Is there a treatment?
Multidrug therapies that use a combination of three medicines can cure leprosy in as little as six months and can prevent disabilities if treatment is given early. The World Health Organization's efforts to eradicate leprosy are based on extending multidrug services to general health facilities in the developing world and reaching those with limited access to health care.
Last summer, the U.S. Food and Drug Administration (FDA) approved the use of thalidomide for the treatment for erythema nodosum leprosum (ENL), a serious inflammatory condition in leprosy patients. Because of its well-known potential for causing severe birth defects, thalidomide will be dispensed only under tightly regulated conditions. Although the FDA had never approved thalidomide for use in the United States before, the agency found the drug's demonstrated effect in treating the skin lesions of ENL convincing. At least 70 to 80 percent of patients enrolled in controlled clinical trials saw their skin lesions improve with thalidomide therapy, compared with 25 percent of the patients given placebos.
Some researchers are attempting to develop effective vaccines for the treatment of this disease but not by using mice. Find out what animal is involved.
Harboe, M., and H.G. Wilker. Secreted proteins of Mycobacterium leprae. Scandinavian Journal of Immunology 48:577-584, 1998.
Marques, M.A., S. Chitale, P.J. Brennan, and M.C. Pessolani. Mapping and identification of the major cell wall-associated components of Mycobacteria leprae. Infectious Immunology 66:2625-2631, 1998.
Mims, C., N. Dimmock, A. Nash, and J. Stephen. Mims' Pathogenesis of Infectious Diseases. London: Academic Press, 1995.
Moura, A.C. and M. Mariano. Lipids from Mycobacterium leprae cell wall suppress T-cell activation in vivo and in vitro. Immunology 92:429-436, 1997.
Rambukkana, A., H. Yamada, G. Zanazzi et al. Role of alpha-dystroglycan as a Schwann cell receptor for Mycobacterium leprae. Science 282:2016-2019, 1998.
Schorey, J.S., M.C. Carroll, and E.J. Brown. A macrophage invasion mechanism of pathogenic mycobacteria. Science 277:1091-1093, 1997.
Smith, D.R., P.Richterich, M. Rubenfield et al. Multiplex sequencing of 1.5 Mb of the Mycobacterium leprae genome. Genome Research 7:802-819, 1997.
Suneetha, L.M., P.R. Satish, R.J. Korula et al. Mycobacterium leprae binds to a 25-kDa phosphorylated glycoprotein of human peripheral nerve. Neurochemical Research 23:907-911, 1998.
For more leprosy (Hansen's disease) links, see http://www.webspawner.com/users/leprosy2/
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