Leave the Armadillos Alone: They're the Only Animals That Can Give You Leprosy

By Veronique Greenwood | April 28, 2011 3:48 pm

dillo

What’s the News: Please back away from the armadillo, ma’am. You can watch them from a distance, even take pictures, but don’t play with or eat Texas’s state mammal: scientists have just confirmed that it is a source of leprosy infections in humans.

How the Heck:

  • About 150–250 cases of leprosy, which is caused by the bacterium Mycobacterium leprae and results in nerve damage if not treated early, are diagnosed in the US each year. Two-thirds of the patients turned out to have contracted the disease abroad in places like Africa, the Philippines, and Brazil, where it’s not uncommon. But a third of the patients had never traveled to locales with a history of leprosy. Many of them lived in the southern U.S., where armadillos roam and are occasionally eaten for meat.
  • Armadillos are known to carry leprosy—in fact, they are the only wild animals other than humans upon which the picky M. leprae can stand to live—and scientists suspected that these anomalous cases were due to contact with the little armored tootsie rolls. But it was hard to prove as long as both humans and armadillos were carrying fairly generic, readily available strains of the bacteria—strains that could have come from anywhere.
  • Now, publishing in the New England Journal of Medicine, scientists have sequenced the genome of a rare leprosy strain found in a Texas armadillo, compared with the strains in human patients, and found them to be the same—very good proof that the disease is passing back and forth between these species.

What’s the Context:

  • Why armadillos? M. leprae is a delicate bacterium and prefers cooler environs, setting up camp in humans mainly in extremities, under fingernails and such. Armadillos, which have a low body temperature for mammals (89° F), are at just the right temperature.
  • How’d they get it? It’s not clear how, but the when is fairly cut and dried: leprosy originated in the Old World, while armadillos exist only in the New World, which means they must have contracted it in the last 400–500 years since European settlement of the Americas began.
  • Armadillos are not alone in carrying diseases dangerous to humans: in addition to birds and pigs that carry flu, many of the chipmunks and rabbits in the western US have fleas that carry bubonic plague.

The Future Holds: Less armadillo on the menu, for starters. But as long as you don’t mess with the critters, you’ll be fine. The researchers hope, though, that this confirmation will help doctors diagnose US leprosy cases faster—if it’s caught early, several years of antibiotics can purge the bacterium from your system before nerve damage occurs. If doctors rule out leprosy because the patient hasn’t left the country, they could be doing them a disservice.

Reference: Richard W. Truman, Pushpendra Singh, Rahul Sharma, Philippe Busso, Jacques Rougemont, Alberto Paniz-Mondolfi, Adamandia Kapopoulou, Sylvain Brisse, David M. Scollard, Thomas P. Gillis, Stewart T. Cole. Probable Zoonotic Leprosy in the Southern United States. New England Journal of Medicine, 2011; 364 (17): 1626 doi:10.1056/NEJMoa1010536

Image credit: chris.vandyck/Flickr

CATEGORIZED UNDER: Health & Medicine, Living World
  • bigjohn756

    Are the armadillos affected by the leprosy or are they just carriers?

  • Lori
  • Metcaffine

    Then why don’t we just politely ask the armadillos if they’re leprous before we eat them? :D

  • er

    Why don’t they figer out a why to just kil the deseas on armadiloes

  • Brian Too

    Wouldn’t cooking kill the leprosy bacteria? I can’t imagine too many people eating armadillo raw. Maybe handling the armadillo is enough to transmit.

  • JesseS

    @Brian Too; I’m not sure about just picking up and handling the armadillos, but the process of cooking an animal is pretty messy, you’d get blood and other bodily fluids on you as you prepared the meat for cooking, and even as you cooked it. I’m pretty certain that even if regular contact wasn’t enough, contacting those would be.

  • Jim Johnson

    I’ve heard the armadillo – leprosy story before, and it’s very interesting; some science blogger should do a blog on it (hint hint).

    As I recall it, back in the late ’50’s or early ’60’s, a medical researcher in Louisiana theorized that armadillos might be able to contract leprosy because of their lower body temperature, which would give medicine a “guinea pig” for a disease guinea pigs (and lab rats) can’t catch. His team tested this and sure enough, in a few years the test armadillos began to show leprosy lesions. (Because they’re not as long lived, they don’t have time to develop the more horrific results of the disease that an untreated human can expect over decades.)

    THEN, leprosy was found in wild armadillos in Louisiana, and the original scientist was accused of allowing the disease to escape the lab into the wild. That theory collapsed however, when infected armadillos were found in a far wider distribution than could be explained by an escape from a lab a decade prior. (If my memory serves, the infection was found even on Caribbean islands – maybe Cuba.)

    At this point, the accepted theory became that armadillo populations were first exposed to leprosy centuries earlier, (probably from the slave trade). This theory has since been bolstered by genetic testing of armadillos’ leprosy viruses.

  • Messier Tidy Upper

    The Future Holds: Less armadillo on the menu, for starters.

    There’s been armadillo on the menu *before* this? ;-)

    Not in any restaurant I’ve been in.

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