Leprosy May Pass Between Armadillos and People

April 27, 2011 -- They may be built like tanks, but armadillos’ natural armor doesn’t protect them from leprosy.

Now a new study shows that some armadillos and people with leprosy in the southern United States are infected with the same bacterial strain. That suggests that the disease, which causes skin lesions and eventual nerve damage, can pass between species, although that circumstance appears to be rare.

The discovery has offered scientists a new way to think about how leprosy may persist in the environment. And it helps to explain how some people contract the disease, especially if they’ve never traveled outside the U. S.

“It’s an excellent scientific publication,” says William R. Levis, MD, a specialist in treating leprosy, which is also called Hansen’s disease, and clinical assistant professor at NYU’s Langone Medical Center in New York City.

Levis says that although the science is sound, he fears the study will misdirect attention in a disease that’s already misunderstood and underappreciated.

“While it’s a nice scientific article, they’re missing the point. The armadillo is not really a major public health issue,” says Levis, who was not involved in the research. “The fact is that leprosy in the United States is an imported disease.”

Tracking Leprosy Through DNA

The study, which is published in the New England Journal of Medicine, compared strains of Mycobacterium leprae, the bacterium that causes leprosy, from 50 patients and 33 wild armadillos captured in five Southern states: Arkansas, Alabama, Louisiana, Mississippi, and Texas.

Something that has frustrated scientists about M. leprae bacteria is that they tend not to change very much over time or between countries, making it tough to pinpoint an infection’s source.

The study used DNA fingerprinting techniques to look for changes to short, repetitive stretches of DNA in the bacterium’s genome called variable number tandem repeats (VNTRs). 

Matching bacterial strains by comparing their VNTR regions is a little like playing slot machines in a casino, says study researcher Richard W. Truman, PhD, a research scientist and captain in the United States Public Health Service in Baton Rouge, La.

“In this case, you’re not playing a slot machine to get all three of your numbers to line up, you’re playing like a casino full of slot machines,” Truman says.

“If it’s like two apple, three apple, four apple, and a 7-bar or something like that, and you find that on four or five different machines simultaneously, that’s the relationship,” he says.

Researchers hit the jackpot when they found a previously unknown strain of M. Leprae in 28 of the 33 wild armadillos they captured and in half of skin samples taken from patients.

The human bacterial samples came from frozen tissue, and in some cases, researchers didn’t have access to the patient’s full history.  In 15 patients who were asked about contact with armadillos, seven said they’d never had contact with the animals, while eight said that they had.

One reported frequently hunting, cooking, and eating armadillos.  His case prompted researchers to caution against handling or eating the animals.