Years-old tissue samples from may harbor Mycobacterium leprae, the , also called leprosy, according to recent research my colleagues conducted.

worldwide in 2021, mostly concentrated in India, Brazil and Indonesia. Since 2010, evidence has accumulated that the nine-banded armadillo, Dasypus novemcinctus, is and potentially .

To investigate this connection, we turned to 10 natural history museums in the U.S. than just public exhibitions. They also host thousands of biological samples, collected over many years. Examining these historical specimens could help researchers identify pathogen prevalence and diversity across time and space.

In our study, we used online repositories such as to identify armadillo specimens held by museums. We then physically examined tissue samples from 159 individual animals from 10 armadillo species. Specimens were collected between 1974 and 2017 from eight countries in the Americas.

Using molecular diagnostic techniques, we identified M. leprae bacteria in muscle, spleen and liver tissues in 18 out of 122 nine-banded armadillos鈥攁 prevalence of 14.8%. All positive samples were collected between 1996 and 2014. Our research allowed us to peek into the immediate past to see that M. leprae was circulating in armadillos in previously unknown locations.

How leprosy is transmitted is still under debate. The bacteria can apparently spread in aerosols and droplets of infected patients. But because some people become sick without being exposed to an infected person or traveling to an area where leprosy is present, researchers think there must be .

In the last decade, molecular examinations of nonhuman samples, water and soils have suggested that wildlife and the environment are potential . Our analysis revealed that the M. leprae strain identified in the positive museum samples is very similar to one that has been circulating in North American armadillos since the 1990s, when transmission of leprosy through wildlife .

In animals, researchers have used museum specimens to study and the .

Scientists less often examine museum archives for . Researchers have, however, identified Tripanosoma cruzi, the agent that causes in natural history museum collections, as well as specimens.

Since approximately 70% of emerging human infectious diseases , examining museum specimens will likely help identify where and when particular pathogens have existed. Ultimately, understanding more about which pathogens are emerging, and where鈥攁s we did with leprosy and armadillos鈥攃an help scientists anticipate potential outbreaks and maybe even head them off.

Scientists discovered in 2008 that another pathogen, . Researchers have yet to untangle the role of this second bacteria in the worldwide incidence of the disease.

All our 159 armadillo samples were negative for M. lepromatosis. But this bacteria has infected humans in , along with .

My colleagues and I prompts further research on the role of nonhuman sources of leprosy transmission across the Americas. is another case study demonstrating that natural history collections can play an important role in human infectious disease research.

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