What is leprosy?
Leprosy has afflicted humankind for thousands of years, being recognised and recorded in many ancient civilisations, but the disease isn't a thing of the past. Every year, up to 300,000 people are diagnosed with leprosy, and up to 3 million people are currently disabled because of it.
Also known as Hansen’s Disease, leprosy is a chronic infection caused by a bacterium called Mycobacterium leprae, which is a slow-growing pathogen that can only live inside its host. This makes research difficult, as animals must be used to grow them and it may take twenty years for symptoms to appear. Leprosy mainly affects the periphery nerves (those outside of the brain and spinal cord), and it’s characterised by skin lesions and sensory loss—eventually, if untreated, sufferers will lose sensation in hands and feet.
Contrary to popular belief, it can’t be caught by touch. Although researchers aren't 100% sure, they believe it’s caught through broken skin or droplets of moisture passed through the air by untreated sufferers. Because symptoms are so slow to appear, people may not realise they’re infected until they’re five or ten years into the disease, but the good news is it’s thought to be partially genetic — so 95% of people are naturally immune.
Today, it’s most common in places of poverty where low standards of living weakens people’s immune systems. Myth and superstition still perpetuate crippling stigma, and those diagnosed with leprosy can be rejected by their families and communities, but quarantine and segregation are unnecessary. Leprosy isn’t as contagious as superstition dictates—those who are treated can lose their infectiousness after as little as two weeks.
References:
http://www.nlm.nih.gov/medlineplus/ency/article/001347.htm
http://www.leprosymission.org/what-is-leprosy.html
It's interesting because like some of its fellow obligate intracellular bacterial diseases, it's so slow in its progress and in the individual bacterial growth, that it's hard for the body to react appropriately, and it's hard to treat because it takes so long for drugs to affect the bacteria. There are some indications that our mitochondria are derived from mycobacterial-related infectious agents, that invaded our cells and never left.
ReplyDeleteI remember my lecturer saying that as a rule of thumb, the older the infectious disease in terms of exposure to humanity, the slower it would be to appear and be less likely to kill you outright.
ReplyDeleteWhereas the newer diseases would be quick, highly virulent and probably lethal, as they have had not enough time to evolve to the new host, as it is not in the pathogens best interest to actually kill their host.
There's a lot of truth to that, Neil Craig, but it depends a lot on the disease. Stuff like ebola, which doesn't easily transfer between humans, has no forcing mechanism to make it less virulent. A particularly interesting case of this is cholera. In populations of people where the primary transmission mode is person-to-person, cholera becomes less virulent over time, whereas in populations of people where cholera is acting as it normally does, as a shellfish pathogen that just runs through people more or less by mistake, it stays just as deadly because its primary forcing mechanism for evolving is involved in its interaction with shellfish and plankton, not humans. On the other hand, with malaria, where the pathogen is transferred best if the person is as close to dead as possible, without actually being dead, so that mosquitos can get to the person with impunity, you see a whole different disease progression pattern with periodic relapses and recoveries.
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