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Leprosy Is on the Move in US, CDC Says

Leprosy, an infectious disease that was once so feared patients were isolated in remote colonies, has emerged in the US Southeast.Armadillos are thought to be the vector.

Leprosy, an infectious disease that was once so feared that patients were isolated in remote colonies, has emerged in the US Southeast


Writing in the Centers for Disease Control and Prevention (CDC) December 2015 Emerging Infectious Diseases, Rahul Sharma PhD r and colleagues report that  Microbacterium leprae. The bacterium that causes leprosy has been detected at new levels in armadillos and humans in Mississippi, Alabama, Georgia, and Florida.


“Leprosy appears to be an emerging infection of armadillos throughout the southeastern United States,” Sharma and colleagues wrote. The slow-moving animals (seen in photo) are known to harbor the bacterium and believed to transmit it to people.



Also known as Hansen’s Disease, leprosy is an infectious disease of the peripheral nervous system caused by an obligate intracellular parasite (M. leprae).


Sharma and colleagues at the National Hansen’s Disease Program Laboratory Research Branch in Baton Rouge, LA, screened 645 armadillos from eight locations in the southern US not known to harbor enzootic leprosy.


In their analysis they found a new leprosy genotype and also found evidence that new genotype had infected humans.


While nine-banded armadillos are known carriers linked to the zoonotic or animal-to-human transmission of leprosy in Texas and Louisiana, Sharma and his team found M. leprae infections in each of the Mississsippi, Alabama, Georgia and Florida sites they targeted. 


The fact that the genotype found in the armadillo has been detected in humans points to cross-species infection, but the mechanism is not really known. The highest risk to humans is thought to be from direct exposure to fresh armadillo tissue or blood--such as found in roadkilled armadillos. 


Armadillos are “the host of choice” for leprosy, possibly because of their cool body temperature. 


In the nine-banded armadillo, leprosy presents in a fully disseminated form involving internal organs as well as the nervous system, making them the ideal subject for research.


 As an obligate intracellular parasite, study co-author Richard W.Truman points out, M. leprae can’t reproduce outside its host making it unwieldy in the lab.


 But an infected armadillo can manifest massive numbers of bacilli in its tissues. 


 According to Truman, although armadillos are common in the southern United States there are only about 200 new human patients a year.   Treatment is usually an antibiotics cocktail on an outpatient basis, and of course patients are no longer quarantined or segregated.


Until the discovery of antibiotics, leprosy was greatly feared and patients were isolated in “leper colonies.” One of the most famous is on the Hawaiian island of Molokai. As of late last year, a few patients were still living there, though the state was then in the process of closing down the colony and moving patients to treatment elsewhere. Truman says the disease is no long so dangerous.


 “In reality leprosy is relatively hard to catch:  its really not highly contagious and probably 95% of the world’s population is naturally immune and would not acquire the infection,” Truman said.

“There are tremendous misconceptions about leprosy…extensive neuritis and nerve damage underlies the gross pathology and deformity we sometimes associate with leprosy…appendages don’t just fall off, lack of sensation makes them very susceptible to secondary injury and trauma.



Writing about leprosy in Disease Models and Mechanisms, Sharma said that in humans, the peripheral nerves are affected early in the course of the disease. The unique ability of M. leprae to invade human peripheral nerves is the root cause of disfigurement and deformity in leprosy, and underlies the extreme social stigma and reduced quality of life that is generally associated with the disease, he wrote.

Antibiotic therapy can halt the disease but it does not reverse nerve damage.

Between two million and three million people worldwide continue to suffer residual neurological effects of the disease, requiring lifelong management. The problem is more pronounced in highly endemic locales in Angola, Brazil, Central African Republic, Congo, India, Madagascar, Mozambique, Nepal and Tanzania, Sharma wrote.