How is an infectious agent transmitted? How does it jump from person to person and sometimes from animal to person? We can breathe it in or swallow it. We can get bitten or scratched, or rub abraded skin against an infected person, or touch a contaminated surface and carry the germ to our face. Figuring out exactly how an infectious agent is transmitted is not always easy. After thousands of years of coming into contact with it, we are still not 100% sure how leprosy is transmitted.
This word, “leprosy,” carries a heavy burden in our collective mind, and the people affected by this persistent disease must in turn carry this burden publicly. It conjures up images of deformities and of a highly contagious malady. Science, however, can help us see more clearly and dissipate the antique fog of dread. Leprosy is not that contagious. Leprosy is curable. And the word “leprosy”—because it was often used as a catch-all in historical texts and because of the stigma that sticks to it—probably should be replaced, as it was in Brazil 26 years ago.
But before science helped us identify the microscopic cause of this disease, leprosy was often seen as punishment from on high.
Blood to cast out the impurity
Humanity has dealt with leprosy for millennia. The oldest physical proof of leprosy might be a middle-aged, male skeleton dug up in India in the late 1990s. The bones carry the marks of a disease that typically causes the appearance of pale or red skin patches where sensation is reduced or lost, but which can also lead to the erosion of facial features, seen on the man’s skull. The skeleton was buried 4,000 years ago.
Historical documents mention leprosy, but the word could mean many things: leprosy itself, but also syphilis, psoriasis, vitiligo, and other skin conditions and parasitic infections. These leprosies were sometimes thought of as a form of divine punishment against the impure. The Book of Leviticus in the Bible lists a convoluted ritual to cleanse healed lepers involving two birds, one sacrificed and the other dipped in its blood. Cultures around the world pointed the finger at curses, possessions and sorcery, and shook nature down in a desperate search for a cure. Our ancestors resorted to drinking blood—from dogs, lambs, corpses, and even babies—to cleanse themselves of leprosy. Scorpions, bees, frogs, and snakes were used for their stings and poisons. The oil from the seeds of trees commonly known as chaulmoogra was used prominently until the middle of the 20th century, surrounded by claims of its effectiveness.
Leprosy left untreated has serious consequences. The loss of sensation that accompanies it is what leads to damage to the extremities and to ulcerations. Daily inspections of the hands, feet and eyes are recommended, as well as exercises to avoid contractures, a shortening or hardening of tissues leading to deformity and rigidity. The disease often affects the eyes as well, with 5% of people with leprosy going blind.
Strangely enough, most people who come into contact with leprosy do not develop the disease. In fact, only about 5% of people exposed to leprosy are successfully infected, and of those only one in five go on to develop the disease, with an incubation period that can last up to 20 years. This means the unlucky few, historically, could more easily be blamed: maybe they had been sinful, maybe they had deserved it.
But leprosy does not strike from above; rather, it is triggered by microscopic bacteria.
Not God’s punishment
In 1873, a Norwegian scientist by the name of Gerhard-Henrik Armauer Hansen discovered the bacterium that typically causes leprosy: Mycobacterium leprae. (A second bacterium, Mycobacterium lepromatosis, was discovered in 2008 and it can cause a specific type of leprosy.) If leprosy is simply a bacterial infection, why do most people who encounter the microbe not get sick? Especially since we know that, over hundreds of years, this little bugger lost part of its genome and has become much more consistent all over the world. If the variability isn’t found in the microbe, where is it coming from?
A recent paper summarizing advances in our understanding of the disease contains this rather amusing answer: “Since the late 1900s, studies have shown that it is the genetic background and not God’s punishment that makes infected individuals develop leprosy.” I’m glad we cleared that up.
Indeed, it turns out that the choice of who develops leprosy and who doesn’t is not due to divine intervention but rather to our own genetic makeup, specifically variations in the genes that encode the building blocks of our immune system. Scientists have speculated that these changes in our DNA may make one person’s immune system react differently to the presence of M. leprae: it may become unresponsive or over-reactive or simply disordered in its response. And that is when the nerve damage and the skin lesions happen, when our immune system has failed to protect us from the bacteria. M. leprae has a taste for certain cells: those found at the surface of our skin, the large eaters in our blood, and the supporting cells of our peripheral nerves. The bacteria move inside those cells and change them. Leprosy has found a new home.
The bacterium is thought to be transmitted via droplets from the nose and mouth from sneezing or coughing, although the exact mechanism of transmission is “still debated.” Unlike a highly contagious disease like measles, leprosy requires continuous and close contact with people who have the infection or, in some cases, with a very strange animal.
In the Americas, leprosy can affect nine-banded armadillos and there are reasons to think that the capture, maintenance, handling, and eating of armadillos can transmit the infection to humans. These armadillos are not the only animals susceptible to the disease: red squirrels in the United Kingdom and some primates can be infected, and certain insects have been shown to have the ability to carry the bacteria and potentially infect others.
The good news is that medicine has evolved beyond snake venom and cups of blood. First, there is the BCG vaccine, typically given to prevent tuberculosis, which has shown to be partly effective at protecting people from leprosy. Then there is a cocktail of three antibiotics—dapsone, rifampicin, and clofazimine—that is used for six to twelve months to cure the disease and that is made freely available by the World Health Organization.
What these drugs don’t do, however, is treat the stigma.
A more dignified language
There is a long history of people with leprosy being confined to asylums and colonies. By the mid-1950s in Japan, for example, 11,000 of them were estimated to be housed in what were called leprosariums, with forced sterilization for the male patients and abortions for the female patients who became pregnant. It was thought that leprosy was hereditary, passed down from one generation to the next. It is not.
The discrimination that affects people with leprosy does not necessarily go away when treatment begins. One of the antibiotics of multidrug therapy, clofazimine, can darken the skin, which can serve as a visible sign that the person is being treated for leprosy and which sometimes changes that person’s racial category. A striking study of the phenomenon in Brazil reveals that “although the pigmentation is usually reversible after 9-12 months, it is sufficient time to suffer racism.”
Leprosy invites ostracization in both its physical manifestation and its treatment, and the word itself is weighed down by antiquated connotations. That is why, following the efforts of a determined dermatologist, a federal law was passed in Brazil in 1995 prohibiting the use of the word “leprosy” in institutional practice and in official documents. The disease became known as hanseníase, after Dr. Hansen who discovered its bacterial origin. Some have argued that the non-stigmatizing term “Hansen’s disease” should be used worldwide instead of “leprosy.” “Leprosy” and “leper” have accumulated so much irrational fear over the centuries as to be dehumanizing; a name like “Hansen’s disease” sheds these superstitions and treats the infection like any other.
Hansen’s disease is still with us today. We know of a little over 200,000 cases worldwide, with fewer than a dozen cases a year in Canada, close to 200 cases a year in the United States, and the vast majority of cases coming from India, Brazil, and Indonesia. It may thus be surprising to hear that the WHO declared it “eliminated at a global level” in 2001. The twist is that “elimination” is defined as fewer than one case per 10,000 population. Maybe this word, like “leprosy,” deserves to be re-evaluated.
-Leprosy, characterized by discoloured skin patches, loss of sensation, and deformities, is caused by a bacterium, although only a small minority of people who come into contact with it go on to develop the disease
-The infection can be cured with a combination of three antibiotics
-Given the heavy stigma that is tied to the word “leprosy,” some have argued that the infection should be renamed “Hansen’s disease,” after the Norwegian scientist who discovered the bacterium that causes it.