Sorry to bump this one up, but I found it interesting. The article below mentions some interesting stuff:
http://www.emedicine.com/derm/topic223.htm"Animal reservoirs of leprosy have been found in 3 species: 9-banded armadillos, chimpanzees, and mangabey monkeys."
"Causes: Leprosy is caused by M leprae, an acid-fast bacillus.
Only the lepromatous form is thought to be infectious.
Exposure to the nasal discharge of those that remain untreated for years is thought to be the main cause of infection.
Most persons are immune to leprosy. Subclinical disease is common in endemic areas, and the infection progresses to clinical disease in only a select few.
Transmission is not completely understood.
In addition to exposure respiratory secretions, exposure to insect vectors and infected soil has been suspected as a possible mode of transmission.
Household contacts of patients are at little risk of acquiring the disease."
A couple of other things I found in a infectious disease text is that it is the first organism to be recognized as a cause of human disease. Mouse footpad will grow the organism, but it has never been cultivated in vitro.