How Armadillos Can Spread Leprosy

These tank-like creatures are the only animals besides us known to carry leprosy

A nine-banded armadillo. Erich Schlegel/Corbis

Last week, offficials in eastern Florida announced the emergence of three new cases of leprosy—the ancient, highly stigmatized disease once handled by isolation—in the last five months. And two of those cases have been linked to contact with the armored, strangely cute critter endemic to the American south: armadillos.

Armadillos are the only other animals besides humans to host the leprosy bacillus. In 2011, the New England Journal of Medicine published an article formally linking the creature to human leprosy cases—people and armadillos tested in the study both shared the same exact strain of the disease. 

So, what’s unique about armadillos that make them good carriers? Likely a combination of body temperature and the fragile nature of the disease. As the New York Times reports, leprosy is a “wimp of a pathogen." It’s so fragile that it dies quickly outside of the body and is notoriously difficult to grow in lab conditions. But with a body temperature of just 90 degrees, one hypothesis suggests, the armadillo presents a kind of Goldilocks condition for the disease—not too hot, not too cold. Bacterial transmission to people can occur when we handle or eat the animal.

But before you start to worry about epidemics or making armadillo eradication plans, find comfort in this: Though Hansen’s disease, as it is clinically known, annually affects 250,000 people worldwide, it only infects about 150 to 250 Americans. Even more reassuring: up to 95 percent of the population is genetically unsusceptible to contracting it. And these days, it is highly treatable and not nearly as contagious as once believed.

And as for armadillos—the risk of transmission to humans is low. Only the nine-banded armadillo is known to carry the disease. And, most people in the U.S. who come down with the chronic bacterial disease get it from other people while traveling outside the country.

And it looks like armadillos are the real victims here. Scientists believe that we actually transmitted leprosy to them about 400 to 500 years ago. Today, up to 20 percent of some armadillo populations are thought to be infected. At least, according to one researcher at the National Hansen’s Disease Program in Baton Rouge, the critters rarely live long enough to be seriously effected by the disease’s symptoms.

Experts say the easiest way to avoid contagion is to simply avoid unnecessary contact with the critters. And, of course, they advise not to go hunting, skinning or eating them (which is a rule the armadillos would probably appreciate, too).

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