Is Leprosy (Hansen's Disease) Contagious?

Leprosy also termed Hansen's disease, is a chronic infection caused by the bacterium Mycobacterium leprae, a rod-shaped organism that stains reddish when an acid-fast stain is applied. Historians suggest leprosy was recognized as a disease as early as 600 BC; because of the disfigurement of individuals with untreated leprosy, people with leprosy have been shunned and isolated for many centuries. Fortunately, current multidrug therapy (MDT) has reduced leprosy so effectively that only a few countries still have individuals with this disease. Currently, the disease is rarely seen in the United States.

Leprosy has been classified into two major types: tuberculoid and lepromatous. However, there are intermediate subtypes (borderline, mid-borderline, and others). Tuberculoid leprosy has a more limited disease pattern and relatively few bacteria located in the infected tissue, while patients with lepromatous leprosy have the widespread disease and much larger numbers of bacteria in infected tissue. These terms are still seen in the literature but are being replaced by the terms paucibacillary (for tuberculoid) and multibacillary (for lepromatous) types.

Mycobacterium leprae can infect armadillos that are indigenous to the southwest United States; occasionally, people can get leprosy if they handle these animals. Another form of leprosy is seen in dogs and cats (canine leprosy). Although canine leprosy is caused by Mycobacterium species, there is no good evidence that canine leprosy is transmitted to humans by pets.

Because symptoms appear so slowly after infection (from about two to 10 years), it may be difficult to tell that someone has leprosy.

• Skin lesions (lumps, bumps, or sores),
• loss of eyebrows, and
• numbness in the skin where lesions are present is often among the first signs and symptoms of leprosy.

Other signs and symptoms include

• thick dry skin,
• muscle weakness or paralysis,
• nosebleeds,
• ulcers (especially on the feet),
• numbness, and/or
• severe pain.

As the disease progresses, extremities may be slowly lost (for example, toes, fingers, and nose). The diagnosis of leprosy can be made by scraping lesions and staining the skin scrapings of lesions and/or mucous secretions with an acid-fast stain to demonstrate the presence of Mycobacterium leprae.

The bacteria are slow-growing; the incubation period for leprosy is about five years (two to 10 years), and it can take as long as about 20 years before symptoms and signs of leprosy (skin lesions, nerve damage, for example) develop in some patients.

Leprosy (Hansen's disease) is spread from person to person. This spread can occur with direct person-to-person contact and/or by contaminated droplets that are released during coughing or sneezing. Individuals who inhale the contaminated droplets can develop leprosy.

Before the 1940s, there was no effective cure for leprosy. Since that time, antimicrobial medications have been used to stop or limit the disease. The key to the cure of leprosy is early treatment before irreparable damage to the patient occurs.

Currently, leprosy is treatable with combination antibiotic therapy that lasts for about six months to two years, depending on the extent of the disease in an individual patient. Most individuals can be cured of leprosy; this occurs when all of the slow-growing Mycobacterium leprae bacteria are killed by the antibiotic treatment and the patient's immune response. However, even though the person is cured of leprosy by antibiotic treatment, damage to organ systems (nerve damage, tissue loss) that has occurred during the infection will not be repaired.

An individual should contact a medical caregiver if they have a high risk of exposure to leprosy and develop any symptoms or signs of the condition. For example, individuals who live in a country where leprosy is endemic, like Brazil, India, Nepal, the Marshall Islands, and several other countries (see references for an extensive list), have a higher chance of developing leprosy.

Armadillos, commonly found in the southern United States, can be naturally infected and carry Mycobacterium leprae. It is possible to become infected after handling these animals. People who handle armadillos and develop any signs or symptoms of leprosy should inform a physician about their contact with armadillos.