Leprosy Cases Are Rising in the U.S. – What Is the Ancient Disease and Why Is It Spreading Now?

Fear of contagion has led to tremendous stigmatization and social exclusion. It was such a serious concern that the Kingdom of Jerusalem had a specialized hospital to care for those suffering from leprosy.

How infectious is leprosy?
Research shows that prolonged in-person contact via respiratory droplets is the primary mode of transmission, rather than through normal, everyday contact such as embracing, shaking hands or sitting near a person with leprosy. People with leprosy generally do not transmit the disease once they begin treatment.

Armadillos represent the only known zoonotic reservoir of leprosy-causing bacteria that threaten humans. These small mammals are common in Central and South America and in parts of Texas, Louisiana, Missouri and other states, where they are sometimes kept as pets or farmed as meat. Eating armadillo meat is not a clear cause of leprosy, but capturing and raising armadillos, along with preparing its meat, are risk factors.

The transmission mechanism between zoonotic reservoirs and susceptible individuals is unknown, but it is strongly suspected that direct contact with an infected armadillo poses a significant risk of developing leprosy. However, many cases reported in the U.S. have demonstrated an absence of either zoonotic exposure or person-to-person transmission outside of North America, suggesting that transmission may be happening where the infected person lives. But in many cases, the source remains an enigma.

Some people’s genetics might make them more susceptible to leprosy infections, or their immune systems are less capable of resisting the disease.

Stigma and discrimination have prevented people from seeking treatment, and as a result, “concealed” cases contribute to transmission.

How do you recognize it?
Leprosy primarily affects the skin and peripheral nervous system, causing physical deformity and desensitizing one’s ability to feel pain on affected skin.

It may begin with loss of sensation on whitish patches of skin or reddened skin. As the bacteria spread in the skin, they can cause the skin to thicken with or without nodules. If this occurs on a person’s face, it may rarely produce a smooth, attractive-appearing facial contour known as lepra bonita, or “pretty leprosy.” The disease can progress to causing eyebrow loss, enlarged nerves in the neck, nasal deformities and nerve damage.

The onset of symptoms can sometimes take as long as 20 years because the infectious bacteria have a lengthy incubation period and proliferate slowly in the human body. So presumably many people are infected long before they know that they are.

Fortunately, worldwide efforts to screen for leprosy are being enhanced thanks to organizations like the Order of Saint Lazarus, which was originally founded in the 11th century to combat leprosy, and the Armauer Hansen Research Institute, which conducts immunologic, epidemiological and translational research in Ethiopia. The nongovernmental organization Bombay Leprosy Project in India does the same.

How treatable is it?
Leprosy is not only preventable but treatable. Defying stigma and advancing early diagnosis via proactive measures are critical to the mission of controlling and eradicating it worldwide.

Notably, the World Health Organization and other agencies provide multi-drug therapy at no cost to patients.

In addition, vaccine technology to combat leprosy is in the clinical trials stage and could become available in coming years. In studies involving nine-banded armadillos, this protein-based vaccine delayed or diminished leprous nerve damage and kept bacteria at bay. Researchers believe that the vaccine can be produced in a low-cost, highly efficient manner, with the long-term prospect of eradicating leprosy.

If health care professionals, biomedical researchers and lawmakers do not markedly enhance their efforts to eliminate leprosy worldwide, the disease will continue to spread and could become a far more serious problem in areas that have been largely free of leprosy for decades.

The World Health Organization launched a plan in 2021 for achieving zero leprosy.

Robert A. Schwartz is Professor and Head of Dermatology, Rutgers New Jersey Medical School, Rutgers University. This article is published courtesy of The Conversation.