Armadillos have never been among the cuddly creatures routinely included in petting zoos, but on Wednesday federal researchers offered a compelling reason to avoid contact with the armored animals altogether: They are a source of leprosy infections in humans.

Using genetic sequencing machines, researchers were able to confirm that about a third of the leprosy cases that arise each year in the United States almost certainly result from contact with infected armadillos. The cases are concentrated in Louisiana and Texas, where some people hunt, skin and eat armadillos.

Leprosy, also known as Hansen’s disease, is an ancient scourge that has largely disappeared, but each year about 150 to 250 people in the United States and 250,000 in the world contract the illness. As long as the disease is identified relatively quickly, treatment with antibiotics — a one- to two-year regimen with three different drugs — offers an effective cure. But every year dozens of people in the United States do not recognize their skin lesions for what they are early enough and suffer lifelong nerve damage as a result.

Part of the problem is that doctors sometimes fail to consider leprosy in patients who have not traveled to parts of the world where the disease is endemic, like India, Brazil, Africa, the Philippines and other islands in the Western Pacific. Two-thirds of leprosy patients in the United States are people who have either lived or worked in such places before coming down with the illness.