Leprosy in U.S. May be Transmitted by Armadillos, Study Finds

A new genetic study on leprosy bacteria reports that armadillos may be a source of infection in the Southern United States. The collaboration between scientists at the Health Resources and Services Administration's (HRSA) National Hansen's Disease Program (NHDP) in Baton Rouge, La., the Ecole Polytechnique Federale de Lausanne and Institute Pasteur in Europe, and the Instituto de Biomedicina in Venezuela sheds light on the potential risk of transmission of leprosy bacteria between armadillos and humans. The risk of transmission is extremely low.

The study, led by Richard W. Truman, PhD, research scientist at NHDP, and published in the April 28 issue of the New England Journal of Medicine, was partially supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.

"Leprosy has been feared throughout human history, and there are still regions in several countries, including in the southern United States, where new cases of this disease continue to occur," said Dr. Truman. "The results of this study will help us better understand where some of these infections originate."

Caused by the bacterium Mycobacterium leprae, leprosy, also known as Hansen's disease, primarily affects the skin and peripheral nerves. It is a chronic infection that afflicts more than 2 million persons worldwide with nerve damage, deformity or disability. Today, leprosy is found mostly in tropical regions of the world; at least 250,000 new cases are reported globally every year, with 150-250 cases occurring in the United States. Leprosy is treatable with antibiotics but is easily misdiagnosed, and delays in therapy increase the likelihood of disability and deformity.

Leprosy was thought to be spread only between humans via respiratory droplets. Armadillos are the only other known natural hosts of leprosy bacteria. These data confirm a long-suspected link between armadillos and the 30 to 40 new cases of leprosy seen each year in U.S.-born Americans who have never traveled abroad to regions where the disease is prevalent.

The new study, scientists compared the gene sequences of M. leprae samples taken from humans and armadillos in the United States. They found that 64% of the human samples had a particular genotype that had never been seen before, and 85% of samples from armadillos shared that same genotype.

"These findings do not change the risk of acquiring leprosy from armadillos, which remains extremely low," says Dr. James Krahenbuhl, director of NHDP. "Armadillos have been suspected as a source of human infection in the Gulf Coast area for 40 years."

"Genetics and genomics have become important tools for studying how diseases behave in natural settings," says Christine Sizemore, PhD, chief of the Tuberculosis and Other Mycobacterial Diseases Section at NIAID. "The data and methods used in this study can be applied in other areas of the world to monitor leprosy transmission and identify other possible environmental reservoirs."