New genetic evidence confirms a long held suspicion that the armadillo, the official small state mammal of Texas, can pass leprosy to humans. The finding should give clinicians a reason to watch for the disease in patients, say researchers, and hopefully lead to earlier diagnosis of the disease.
“There is no need to slaughter the animals or get panicked,” says Pushpendra Singh, a molecular microbiologist at École polytechnique fédérale de Lausanne (EPFL) in Switzerland and a co-author on the paper published 28 April in The New England Journal of Medicine. “But we proved something which was hypothesized for a long time.”
Leprosy (otherwise known as Hansen’s disease) is a highly stigmatized disease caused by the bacterium Mycobacterium leprae and is rare in the United States. Around 150 cases are diagnosed in the US each year, a third of which appear to be contracted locally. Contrary to popular belief, leprosy is treatable with antibiotics and doesn’t cause lasting damage as long as it’s caught early. Roughly 95% of humans are immune to the disease, which is so uncommon in the US that when cases do arise, many physicians do not recognize it immediately.
“It’s very important to diagnose it in time so that’s why we insist that clinical suspicion is very important,” says Singh.
The nine-banded armadillo (Dasypus novemcinctus) is the only animal that manifests leprosy the way humans do. It’s a reservoir for leprosy in the southern states of Arkansas, Alabama, Louisiana, Mississippi and Texas, where infection can exceed 20 percent in some areas. Human contact with armadillos was already known to be a risk factor for contracting leprosy, but no one had ever shown convincingly that armadillos were passing the disease to humans.
Researchers from the Global Health Institute at EPFL and the National Hansen’s Disease Program at the Louisiana State University School of Veterinary Medicine in Baton Rouge, have now confirmed with genomic data that the same strain infecting armadillos in the southern US is the one infecting many patients there. This is convincing evidence that the armadillo is the source of most of the locally contracted infections, they say.
The teams sequenced the genomes of one strain of M. leprae from an armadillo, and three U.S. patient strains and found that all were essentially identical. Then the researchers compared that strain with M. leprae samples from Asia and Brazil to reveal mutations unique to the North American strain. That same strain, which isn’t found anywhere else in the world, was found in 28 of 33 wild armadillos and 25 of 39 US patients living near areas with infected armadillos.
Though people shouldn’t panic, they should avoid contact with armadillos through hunting, cooking or eating, Singh says. In addition, clinicians should add leprosy to their list of possible diagnoses when a patient has skin lesions that don’t respond to common treatments. Delayed diagnoses could mean permanent nerve damage and deformity. And as armadillos expand their range, they should be monitored while the public is made aware of the health threat.