What do armadillos and human beings have in common? They can both become infected with leprosy, one of the oldest and most dreaded bacterial diseases known to man.

Humans contract leprosy through a tiny and colorless bacterium that is hard to spot. Armadillos can get the disease in the wild. When blood drawn from armadillos captured in the wild was tested, it showed that the animals had been exposed to the bacterium before capture and had developed antibodies to leprosy. In laboratories, armadillos are given the disease artificially to help find effective vaccines for treatment of this disfiguring illness. Because these bacteria are difficult to grow in a laboratory, vaccines being developed for leprosy currently depend on artificially infected armadillos for their production.

Why an armadillo?

The armadillo has a relatively low body temperature of 32 to 35^o C, which the bacillus prefers. Other advantages of the football-sized animal include litters of identical quadruplets (useful for control and experimental studies), a relatively long life span of 10 to 15 years, a tendency not to bite, a tolerance to laboratory procedures, and a large population, numbered at about 30 million, in the United States.

The use of armadillos infected with leprosy has also enabled researchers to search for new drugs and to test whether older ones induce resistance after prolonged treatment. Diseases such as leprosy often require long-term therapy. The effectiveness of single-drug therapy with fluoroquinolone, for example, gradually decreases as the bacillus becomes more resistant to it. In contrast, when the drug is administered with two other antibiotics —dapsone and rifampicin—fluoroquinolone remains effective. Mild cases of leprosy may require just two drugs for six months, whereas severe cases may call for three drugs and two years of treatment. The recurrence of disease once the drugs are stopped is low, but the drugs cannot reverse any nerve damage that has already occurred.

New research by HHMI Investigator Kevin Campbell and his colleagues holds the promise of preventing nerve damage in leprosy patients. Read more about his work at http://www.hhmi.org/news/campbell2.htm

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