The Research Brief is a short take about interesting academic work.
The big idea
Years-old tissue samples from armadillos in museum collections may harbor Mycobacterium leprae, the bacteria that causes Hansen’s disease, also called leprosy, according to recent research my colleagues and I conducted.
Leprosy can cause nerve damage that, without early effective treatment, can lead to paralysis and blindness in the most severe cases. Approximately 140,000 new patients were diagnosed worldwide in 2021, mostly concentrated in India, Brazil and Indonesia. Since 2010, evidence has accumulated that the nine-banded armadillo, Dasypus novemcinctus, is transmitting leprosy to people in North America and potentially elsewhere.
To investigate this connection, we turned to 10 natural history museums in the U.S. These institutions offer more 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.
Molecular diagnostic techniques identified the leprosy-causing Mycobacterium leprae bacteria in archived tissue samples from 14.8% of nine-banded armadillos tested.
Daniel Romero-Alvarez
In our study, we used online repositories such as VertNet 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 – a 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.
Why it matters
How leprosy is transmitted is still under debate. The bacteria can apparently spread in aerosols and droplets released by the coughs or sneezes 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 another way it spreads.
In the last decade, molecular examinations of nonhuman samples, water and soils have suggested that wildlife and the environment are potential sources of leprosy. 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 was still only suggested.
What other research is being done
In animals, researchers have used museum specimens to study snake fungal disease and the chytrid fungus that affects frogs.
Scientists less often examine museum archives for pathogens that…
