Ill roadkill: Although they don't usually show outward symptoms in the wild, common U.S. armadillos are often infected with a transmissible form of leprosy.
Image: Wikimedia Commons/NASA/Ken Thornsley
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Leprosy was one of the last things on dermatologist John Abide's mind when a 78-year-old man walked in for a screening at the doctor's Greenville, Miss., practice. Unbeknownst to the man, two large red bumps had formed on his back. Abide diligently tested samples to make sure they did not indicate tuberculosis. When the results came back positive for atypical mycobacteria, another doctor suggested sending the samples away to have them tested for leprosy.
"I thought that was a waste of time," he says. When they came back positive, Abide was stunned. "I didn't know that they still studied it—or that it was still in existence."
In the next few years, he came across two other local patients—an 81-year-old woman with a growth above her left elbow and a 73-year-old man with a red rash on his chest—who also tested positive for leprosy, also known as Hansen's disease.
None of them had been traveling where leprosy was common, but all three reported close contact with armadillos. Did Abide ever imagine as a Mississippi dermatologist he would be treating leprosy patients? "No, indeed," he says. "It's kind of scary."
That humans would catch the disease from these armored animals might seem unlikely. The nine-banded armadillo (Dasypus novemcinctus) is common across parts of more than a dozen southern states. Leprosy is not. Although many cases might go undiagnosed, in the U.S. there are only about 150 to 200 new cases reported each year—and about 3,600 people being treated for the chronic condition. And the majority of the cases, roughly 70 percent, are presumed to be from people who picked up the bacteria while traveling abroad.
But a new study, published in the April 28 issue of The New England Journal of Medicine, found a new strain of the disease, common to both local people and armadillos, suggesting that the animals are, indeed, a wild reservoir for leprosy.
Improbable couriers
Leprosy might sound like an exotic, extinct disease, locked in the annals of history or sequestered in quarantine colonies in far-off lands. But it persists here in the U.S., and new research suggests, in addition to being spread by infected people, it is also being carried on the leathery backs of ambling armadillos.
By a fluke of genetics, armadillos and humans seem to be the only two species that are natural habitats for the bacterium Mycobacterium leprae, which causes the disease. And sometime in the past four centuries, since leprosy landed in the New World via European explorers, it made its way into these insectivores, which are also common throughout Mexico.
In addition to an unexpected genetic predisposition for leprosy, armadillos have one thing that might make them more conducive mammalian hosts: a cool body temperature. At about 32 degrees Celsius (90 degrees Fahrenheit), their core temperature is cooler than that of many mammals, which might make for a better host environment for the bacteria. In the wild, a leprous armadillo might not appear to be different from an uninfected one, Richard Truman of the U.S. Health Resources and Service Administration's National Hansen's Disease Program at Louisiana State University and a co-author of the new study explains. Sick animals will likely be picked off by predators and not survive long enough to develop obvious symptoms.
Fortunately, M. leprae is a finicky organism. It cannot survive for long outside of a living cell—a couple hours on a microscope slide, and maybe a couple weeks in moist soil, Truman notes. And most people—about 95 percent of us—are naturally immune to it. A person's likelihood of getting the disease, even with close contact, is slim and rests on variables such as his or her genetic makeup and immunologic strength.
Because the bacterium that causes leprosy cannot be grown in lab dishes, finding that the armadillo could also carry the disease proved to be a boon to researchers bent on finding new treatments.
Aside from the characteristic skin sores, in humans leprosy can cause lasting nerve damage in the extremities and sensory deterioration. Rather than shipping the afflicted away to colonies, the disease can now be treated with a long course of three drugs (rifampicin, clofazimine and dapsone), which are not without their own side effects.
The disease was only confirmed in wild armadillo populations in 1975. And the new study pinpoints Alabama, Arkansas, Louisiana, Mississippi and Texas as the states where the newly described genotype was found. As Truman points out, the genotype itself might not be so new, but rather, researchers now have more advanced genomics tools to recognize it.
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7 Comments
Add CommentThis is not news. The connection between humans, armadillos, and leprosy has been known for close to 80 years. Anyone living in armadillo country knew it.
Reply | Report Abuse | Link to thisP.S. Get rid of the commercial spam.
Would this be JUST like the researcher who caught the plague because he was iron overloaded ? Could the elderly be especially prone to catching leprosy BECAUSE of age-related iron accumulation / hemochromatosis ?
Reply | Report Abuse | Link to this"Casadaban's lab bugs were weak because they have trouble taking up iron, which they need to make crucial enzymes. Unfortunately, unbeknownst to him, Casadaban had haemochromatosis, a genetic disorder in which people accumulate high levels of iron in their blood and organs. When the weakened bacteria somehow hit Casadaban's blood, they suddenly received an influx in iron and regained their strength."
There is a possibility a person IS predisposed to catching leprosy since iron IS being targeted ?
Reply | Report Abuse | Link to this"Based on the chemistry of Mycobacterium leprae, the target systems for new anti-leprotics are identified. These systems include the cell wall, the catabolism of reactive oxygen species, the metabolisms of carbon sources, the amino acid metabolism and the uptake of iron."
I am a resident of Louisiana. There is an old local saying,"Cajuns will eat anything that don't eat them first".
Reply | Report Abuse | Link to thisI actually have a Cajun recipe book that tells how to prepare and cook armadillo.
The state figured out long ago that armadillos did carry leprosy and issued a stern warning to the people not only don't eat them, but don't handle them either. We were ahead of the scientific curve.
Like Abide, though I knew of leprosy in nine-banded armadillos, I had never heard of them as a a reservoir for human disease. I am however still puzzled; I would not have thought that there could be much threat from dried material; is the reaction pure revulsion, or is there a rational basis for such apparently excessive caution in refusing to handle material that, on of the face of it, could hardly be infectious ?
Reply | Report Abuse | Link to thisGiven that leprosy does not seem to infect tissues at a high temperature, and of the factor that this has been known for a long time, could anyone please tell me, bearing in mind that for a very long time no really effective antibiotic was known: Have hot compresses either been used at all in treatment, or could they be effective against at least the superficial skin infections? High temperatures and fevers have after all, not only appeared in nature as effective defences against certain infections, but have been used against various other diseases. How about leprosy?
This is a little creepy to me. I saw an armadillo on the way to take my son to his <a href="http://www.manningorthodontics.com">orthodontist in greenville nc</a>. I thought it was a little odd, but then I read this article and now I'm more just a little creeped out. I don't want to get leprosy.
Reply | Report Abuse | Link to thisAn Armadillo does seem like an unlikely place to get an ancient disease but good to know. I don't think we have any armadillos near my dentist office in Danville VA but I'll make sure to watch out any time I'm out in armadillo country. http://www.danville-dentist.com/site/sitemap-page
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