Leprosy
Pathogen: Mycobacterium leprae
Category of Pathogen: bacteria
Name of the disease caused by the pathogen: Hansen’s Disease, more commonly known as Leprosy.
Symptoms of Infection:
- Leprosy has a long incubation time, ranging from a few weeks to as many as 10 years before the development of symptoms. It is a very slow moving disease.
- M. leprae prefer cooler environments, so evidence of the disease is usually restricted to the skin, nose, mouth, and nerves near the skin. Skin lesions and loss of sensation can occur.
- Blindness and enlarged peripheral nerves are common.
- There are two forms of the disease: tuberculoid and lepromatous leprosy. Tuberculoid leprosy is the less severe form of the disease, causing only a few, small lesions on the skin. Lepromatous leprosy causes higher numbers of lesions which contain many more bacteria.
- Hard nodules and folds of skin form on the face, potentially causing the nose to collapse, causing a “lion-like” appearance.
- Because the disease causes nerve damage, affected individuals do not notice injuries, which can get infected by other types of bacteria causing additional disfigurement.
- Contrary to popular belief, body parts do not fall off, but damaged bones and tissue can be reabsorbed by the body, which can lead to shorter digits.
Primary Host: Armadillo
Secondary Hosts: Mice, humans
Although armadillos and mice can have M. leprae, they do not have the same symptoms as humans. Nerve damage does not occur, but if the bacteria are present in the animals’ internal organs, it can be fatal.
Route of Transmission: Respiratory Droplets
Ro: <1 in most areas, =1 in a select few countries where it is considered endemic (Brazil, Mozambique, Tanzania, and Nepal comprise 90% of cases).
Prevalence: 212,802 cases at the beginning of 2008
Generation Time: 12 to 13 days
Mortality Rate: Unknown, however Leprosy is rarely fatal.
Morbidity Rate: Less than 1 case per 10,000 population. If left untreated, disfigurement is likely.
Is it preventable? How? It is not preventable in the traditional sense. However, 95% of the general population are naturally immune. Immunity to M. leprae stems from Cell Medical Immunity (CMI), which is determined by T lymphocytes.
Does the disease trigger long-lasting immunity? No
When was the pathogen first described and is there evidence that it was around much earlier than that?
- Documents dating back to 600 BC were found accurately describing the disease in India, where the disease most likely originated.
- The bible has multiple references to Leprosy. However, the descriptions do not resemble current-day Leprosy.
- Although it did not appear in literature until 600 BC, a 4,000 year old skeleton was found in northwestern India with signs of the disease. That means Leprosy could have been around since 2,000 BC!
What is the economic impact of the disease? The disease has little impact on most areas today because the prevalence of the disease is dropping. However, there is still a social stigma associated with leprosy. Leper colonies are still present in some countries where the disease is endemic, which can have a negative economic impact on society. Because of the nature of the disease, isolating contracted individuals is not necessary and can ultimately hurt the community by ostracizing people who could otherwise be productive members of society.
The coolest thing about the disease? While the disease still has a social stigma associated with it, it should not be feared. The majority of people who contract the bacteria would not develop the disease. Additionally, Leprosy is curable after the discovery of multi-drug therapy with the drugs rifampicin, dapsone, and clofazimine.
Citations:
“Leprosy,” MedIndia. 28 August 2009. http://www.medindia.net/education/familymedicine/Leprosy-Epidemiology.htm
“Leprosy,” Microsoft® Encarta® Online Encyclopedia 2009
http://encarta.msn.com © 1997-2009 Microsoft Corporation. All Rights Reserved. http://encarta.msn.com/encyclopedia_761578788/leprosy.html
“Leprosy (Hansen’s Disease)” Center for Disease Control and Prevention. 28 August 2009. http://www.cdc.gov/nczved/dfbmd/disease_listing/leprosy_ti.html
“Leprosy Today,” World Health Organization. 28 August 2009. http://www.who.int/lep/en/
“Understanding Leprosy” Rising Star Outreach. 28 August 2009. http://www.risingstaroutreach.org/understandingleprosy
