Hansen s Disease. by Kameron Petok

Transcription

1 Hansen s Disease by Kameron Petok Disease Name and History Hansen s disease is also known as Leprosy. The microbe that causes it was first discovered by Dr. Gerhard Henrik Armauer Hansen of Norway in The etiologic agent of Hansen s Disease is Mycobacterium leprae. (1) Throughout history, this disease has been misunderstood and even feared. For example, during the Middle Ages in Europe, people who suffered from it had to wear certain kinds of clothes and even walk on a different side of the street because of such a negative stigma correlated with the infection. (1). Though the infection is not highly contagious, the look of it even gave the name lepers to those infected and caused people to isolate them for fear that they would get it. These reactions to Hansen s disease are due to the noticeable symptoms on the skin of the face and arms such as lesions and nodules. It, therefore, makes sense that individuals with Leprosy were once thought to have a curse upon them or a punishment from God. There is such a strong stigma that even, to this day, Leprosy patients are sometimes treated in separate hospitals or areas (1). When Dr. Hansen identified the germ that causes Leprosy under a microscope, he also disproved previous beliefs that it was hereditary, caused by a curse or a sin. General characteristics and Tests for Identification The Mycobacterium leprae that causes Hansen s disease is a strongly acid fast, rodshaped bacillus. This shape has parallel sides and rounded ends. The bacteria grow optimally at 30 degrees Celsius and prefer the outer, cooler portions of the human body. (2) They contain capsules that the Mycobacteria genus shares. The bacteria group together in masses called globi and are commonly describes as looking like bundles of cigarettes or cigars. (3) The bacillus can have different forms with slightly different shapes (including spherical) and can range anywhere from 1-8 micrometers by micrometers in size. They are gram-positive but cannot be stained easily by traditional gram staining because of the waxy lipid mycolic acid in their cell walls. (4) To diagnose an infection, skin smears from the elbow, ears, or knees, skin biopsies from the edges of active patches, or nerve biopsies from thickened nerves can identify the bacteria. The further presence of an acid-fast bacilli in these samples after an acid-fast stain confirms the diagnosis of Hansen s disease. (5) A similar slit skin smear can be used to multiply the acid-fast bacteria in an infected skin sample and identify M. leprae. (2) Transmission and Reservoirs M. leprae is not highly contagious but is believed to be spread from person to person through nasal secretions and droplets. The exact way it transmits is not known. But it is known that, in order to catch Leprosy, a person needs to be in close contact with an untreated, infected individual for many months. (5) You cannot become infected by the bacterium by simpler forms of contact with infected people like shaking hands, hugging, and sitting with someone for a meal. The bacteria can also infect skin through compromised barriers like cuts and scrapes but cannot infect intact skin. A reservoir that is regularly infected by M. leprae are some armadillos in the South part of the United States. The chance of getting the infection from them is still very low even after coming into contact with this armadillo. (5) The source of an infection is hard to find

2 because the bacteria grow very slowly in the body and take a long time to cause any visible symptoms (up to 20 years in some cases). Humans are the main reservoir for Hansen s disease on top of armadillos. But some other naturally infected reservoirs include non-human primates like the African chimpanzee, sooty managabey, and cynomolgus macaque (6). Signs and Symptoms With Hansen s disease, it may take five years or longer for these signs and symptoms to show up. They may do so in as little as one year, but this is not likely. A key sign of leprosy is a skin lesion (single or multiple) that is normally less colored than the skin around it. Several kinds of these can occur but the most common are macules (flat), papules (raised) and/or nodules. (7) A symptom of Hansen s disease is losing sensation on skin lesions. Damaged/thickened nerves can also cause weak muscles near a lesion. This is because M. leprae survives ingestion by macrophages and eventually invades cells of the myelin sheath of the peripheral nervous system. (2) Some of the first symptoms to show up are pains in joints, pins and needles sensations, numbness, and weight loss. (8) There are six classifications of the degree of infection ranging from indeterminate leprosy (most mild form) to lepromatous leprosy (where signs may include limb weakness, hair loss, aseptic necrosis, and disfigurement of many areas, including the face). (8) Virulence factors The M. leprae that causes Hansen s disease is hard to study because it cannot be grown on artificial media. Cells that form a myelin sheath around a nerve cell s axons are called Schwann cells. This is where the bacterium starts infection and attaches itself by using adhesins. More specifically, a phenolic glycolipid called PGL-1 binds to a protein on the basal lamina of the Schwann cell called laminin-2 and may induce apoptosis here. (9) This is because the temperature of the peripheral nervous system is the nearly identical to the bacteria s optimal growth temperature. The bacteria prevent the binding of phagosomes and lysosomes to escape the immune defenses. And the nerve damage can result from the cell-mediated immune response due to their presence. (2) The waxy mycolic acid in their exterior coating allows M. leprae to initially become phagocytized by macrophages, where they survive and replicate. Control/Treatment Multiple drug therapy is used to treat Hansen s disease. A combination of Dapsone, rifampin, and clofazimine are the main drugs used. Dapsone was the only drug used to treat Leprosy for many years until drug resistant strains showed up. (10) Paucibacillary leprosy is when a lesion contains no M. leprae bacilli and Dapsone with rifampin are sufficient to treat this form. On the other hand, all three drugs should be used to treat multibacillary leprosy, which is when multiple bacilli are detected in a skin biopsy. The World Health Organization standard for paucibacillary leprosy is 6 months treatments and, for multibacillary leprosy, 24 months. (2). To cure a mild single lesion paucibacillary leprosy, a one-time dose of multiple drugs (rifampin, minocycline, and ofloxacin) is sufficient. Steroids like prednisone, along with other antiinflammatory drugs, are used to control nerve pain/damage because antibiotics cannot. (11) Prevention/Vaccine Info The prevention of Leprosy depends on how early a diagnosis is made and how early a treatment is given when diagnosed. This can help halt the transmission of the disease from

3 infected to noninfected individuals. (12) People who live with Leprosy diagnosed others should be monitored closely for any signs/symptoms. The WHO has created blister packs that contain 28 days of medication for both forms of Leprosy. But, in poorer areas, people may not be able to routinely go to a clinic to have these administered. So, discipline is required at home to take medications correctly so symptoms may be helped. There is no single vaccine that completely prevents Hansen s disease. But there are some being tested that may aid in prevention. (12) In terms of the best possible prevention, the BCG (Bacillus Calmette-Guerin) vaccine can provide variable levels of protection in certain populations because it treats Tuberculosis, which is caused by a Mycobacterium species like M. leprae. (12) More than half of global Leprosy patients live in India. The first exclusive vaccine for Leprosy, called mycobacterium indicus pranii (MIP), has been implemented after trials there. It does not prevent or cure Leprosy completely, but it does help infected individuals recover faster. It also has been shown, if given to those close to diagnosed patients, to bring down cases by 60% in three years. (13) Local/Global Statistics India has the most cases (both new and total number of) of Hansen s disease in the world. As of 2016, the number of new cases (prevalence) in India was a little over 130,000, which account for 63% of global prevalence. Brazil, Indonesia, Democratic Republic of Congo, and Ethiopia make up most of new cases with 86.14% distributed among them (also in 2016). (14) The current prevalence of Leprosy is about 0.34 per 10,000. (15) The highest rates are in tropical countries like Asia and Africa. Around 100 new cases of Leprosy are reported in the United States each year. (11) Most of these cases happen because people from the tropical countries (mentioned in the figure) travel to the U.S. from places that are endemic for the bacterial infection that causes Leprosy. (11) According to one report, from 1994 to 2011, there were only 2,300 new Leprosy cases in the United States. (11) The same report showed that the incidence rate for Leprosy for the U.S. was 0.43 cases per 1 million from 2009 to The rate of Leprosy for people born outside the United States is 14 times higher than for those born in the United States.

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5 References (1) Barrett, D. R. (2005). History of Leprosy. Retrieved May 6, 2018, from Stanford University website: (2) Tortora, G. J., Funke, B. R., & Case, C. L. (2016). Chapter 22. In Microbiology An Introduction (12th ed., pp ). Pearson Education, Inc. (3) Microbiology of M. Leprae. Retrieved May 6, 2018, from World Health Organization website: (4) Sangwan, A. Mycobacterium Leprae: Morphology, Cultivation, and Structure. Retrieved May 6, 2018, from Biology Discussion website: (5) Hansen's Disease (Leprosy). (2017, February 10). Retrieved May 6, 2018, from Centers for Disease Control and Prevention website: (6) Barrett, D. R. (2005). Biological Characteristics. Retrieved May 6, 2018, from Stanford University website: (7) What is Leprosy. (2018). Retrieved May 6, 2018, from World Health Organization Southeast Asia website: (8) Davis, D. C. P. (2017, September 8). Leprosy (Hansen's Disease) (M. C. Stoppler, Ed.). Retrieved May 6, 2018, from MedicineNet.com website: (9) Mycobacterium Leprae. (2010). Retrieved May 6, 2018, from Pathogen Profile Dictionary website: (10) WHO Model Prescribing Information: Drugs Used in Leprosy. (2017). Retrieved May 6, 2018, from World Health Organization website: (11) Gardner, S. S. (Ed.). (2017, April 19). Leprosy Overview. Retrieved May 6, 2018, from WebMD website: (12) Doerr, S., Dr. (2010, December 10). Leprosy (C. P. Davis, Dr., Ed.). Retrieved May 6, 2018, from emedicinehealth website:

6 (13) Narayani, P. (2016, August 20). World's first leprosy vaccine... Retrieved May 6, 2018, from The Times of India website: Worlds-firstleprosy-vaccine-developed-in-India-to-go-on-trial/articleshow/ cms (14) Leprosy reported cases. (2011). Retrieved May 6, 2018, from Knoema website: (15) Thomas, L., Dr. (2017, January 26). Leprosy Epidemiology. Retrieved May 6, 2018, from News Medical website: Epidemiology.aspx