Blog: Armadillos and leprosy

Armadillos and leprosy

Armadillos are one of the few animals that are known to be able to have leprosy and that can transmit the infection. For a long time there has been a scientific debate about where armadillos got their leprosy from, and whether they can infect humans, or whether humans can infect them. Leprosy is now known to be a zoonosis.[1]

When Christopher Columbus “discovered” America, many new species were described for the first time by Europeans. One of those was the armadillo. The armadillo was an animal that was unlike anything that the Europeans had previously seen. Many naturalists sought to draw the animal. Many of them drew them from verbal descriptions rather than seeing real animals, which lead to the drawings looking a bit odd, including some that looked like rhinos. This stemmed from Sir Walter Raleigh’s description where he said that the armadillo had armor like a rhinoceros.[2] Other drawings depicted the armadillo as something so big that a man could sit on it. Armadillos became a symbol for America (south and north as there was no distinction at this time) in paintings and other art.

Nine-banded armadillo in leprosy research

In 1971, scientists Kirchheimer and Storrs found that the nine-banded armadillo and the seven-banded armadillo can be infected with leprosy. Because leprosy cannot be cultivated in vitro (meaning that it cannot be cultivated in an artificial environment, outside a living body), scientists had been looking for animals that could be infected with leprosy so that they could do research on the disease. Armadillos, particularly the nine-banded armadillo, became a standard experimental animal because it mimicked leprosy in humans and produced many bacilli.

Zoonotic transmission of leprosy

While searching for armadillos to do research on in the US in 1975, Kirchheimer and Storrs discovered natural M. leprae infection in the nine-banded armadillo.[3] This sparked the question of how these animals managed to get this disease. Scientists believe that leprosy most likely originated in Eastern Africa or the Near East, and later spread to Europe.[4] Leprosy could have been brought to America by early European explorers.[5] Armadillos may have been infected by people infected by leprosy who handled them.[6] Armadillos with natural M. leprae infection have been found in the southern U.S., Brazil, Mexico, Colombia, and Argentina.[7]

The impact of leprosy in armadillos for humans continues to be researched. Armadillos have been shown to transmit M. leprae to humans who have been in contact with them on several occasions in Texas, Louisiana, and Florida.[8] International research led by Colorado State University surveyed people living in the town of Beltrella in Brazil concerning their contact with armadillos. They found that 65% of the people had come in contact with, cleaned, prepared or had eaten armadillos at least once a year. They found a positive leprosy antibody titer in 63% of the people who took part in the survey, but could not find a significant difference based on whether they had or had not handled the armadillos. The people who ate more of the meat, in some cases armadillos were consumed twice a week, had a much stronger antibody count.[9]

Surveys like this show that there is still a lot to learn about the zoonotic transmission route for leprosy. If leprosy is present in armadillos, there could be other animals that are sources of leprosy. For example, scientists studying wild chimpanzees have found some infected with M. leprae.[10]

Although we are unsure how leprosy spreads from armadillos to humans or vice versa, precautions should be taken around armadillos. Armadillos may carry M. leprae, so it is important to educate people on how to handle armadillos and not increase the likelihood of transmission. It is also important to say that the solution is not to kill wild infected armadillos, because killing the animal may increase the risk of infection.

Voluntarily written for nlrinternational.org by Marion Jørgensen. Opinions stated in the article are on personal title of the author and do not necessarily express NLR’s views. 

[1] Sharma R, et al., “Zoonotic Leprosy in the Southeastern United States”, Emerg Infect Dis. 2015 Dec;21(12):2127-34. doi: 10.3201/eid2112.150501.

[2] Cassidy Cash, “Armadillos with Peter Mason,” 5 September 2022, https://www.cassidycash.com/armadillos-with-peter-mason/

[3] Ilanna Vanessa Pristo de Medeiros Oliveira, Patrícia Duarte Deps, and  João Marcelo Azevedo de Paula Antunes, “Armadillos and leprosy: from infection to biological model,” Revista do Instituto de Medicina Tropical de São Paulo 61 (2019), https://www.scielo.br/j/rimtsp/a/fksJWrZxNRtGSk8ygqqdcxB

[4] Marc Monot et al., “On the origin of leprosy”, Science 308, 1040-1042 (2005), https://www.science.org/doi/10.1126/science/1109759

[5] Richard Truman and Paul E. M. Fine, “‘Environmental’ sources of Mycobacterium leprae: Issues and evidence”, Leprosy Review 81 (2010): 89-95, https://researchonline.lshtm.ac.uk/id/eprint/2927/1/2927.pdf

[6] Leslie A. Blake et al., “Environmental Nonhuman Sources of Leprosy”, Reviews of Infectious Diseases, Vol.9, No.3 (1987)

[7] Ilanna Vanessa Pristo de Medeiros Oliveira, Patrícia Duarte Deps, and  João Marcelo Azevedo de Paula Antunes, “Armadillos and leprosy: from infection to biological model,” Revista do Instituto de Medicina Tropical de São Paulo 61 (2019), https://www.scielo.br/j/rimtsp/a/fksJWrZxNRtGSk8ygqqdcxB

[8] Mary Guiden, “New evidence that wild armadillos spread leprosy to humans”, 29 June 2018, https://cvmbs.source.colostate.edu/new-evidence-that-wild-armadillos-spread-leprosy-to-humans/

[9] Moises B. da Silva et al., “Evidence of zoonotic leprosy in Pará, Brazilian Amazon, and risks associated with human contact or consumption of armadillos”, Plos Neglected Tropical Diseases (2018), https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0006532

[10] Hockings, K.J., et al., “Leprosy in wild chimpanzees”, Nature 598, 652–656 (2021), https://doi.org/10.1038/s41586-021-03968-4