Armadillos Linked with US Leprosy Cases

Armadillos appear to have transmitted a unique strain of the bacterium that causes leprosy to humans in the southern United States. (Image: John and Karen Hollingsworth/USFWS)

Armadillos have been implicated in infecting humans in the southern United States with a never-before-seen strain of the bacterium that causes leprosy.

Researchers have known for decades that armadillos harbor Mycobacterium leprae, which causes leprosy, also known as Hansen disease. But cross-species infection is rare. In today’s New England Journal of Medicine, researchers in Switzerland and the United States report on extensive DNA analyses they conducted to link human leprosy cases with the unique strain of M lepraefound in armadillos.

After discovering identical strains of M leprae in a wild armadillo and in 3 US patients with leprosy, investigators cast a wider net. They sequenced the genome of M leprae specimens isolated from 33 wild armadillos in 5 southern states, 50 US outpatients at a clinic in Louisiana, and 64 patients in Venezuela. Then they compared the results with genome sequences of other strains of M leprae from Europe, Brazil, and Asia.

The bacterium’s genetic characteristics did not match any others in a worldwide database. Investigators found the unique bacterial strain in 28 of the armadillos and in 22 US patients. None of the 22 patients had worked or lived abroad in an area where leprosy is endemic; in most of the 150 US leprosy cases reported annually, patients acquire the illness outside of the United States.

“A high percentage of unrelated leprosy cases in the southern United States involved infection with the same unique strain of M leprae that occurs naturally among wild armadillos in the region,” the study authors wrote. Armadillos are the only nonhuman reservoir of the bacterium.

The authors said physicians should consider leprosy in the differential diagnosis of patients with chronic skin lesions who may have been exposed to M leprae through contact with armadillos. Some populations cook and eat armadillo meat.

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