Humans can get leprosy through contact with armadillos

Researchers have proven through genetic testing that a certain strain of leprosy can be transmitted between humans and armadillos. These armadillos are thought to be the source of many of the cases of leprosy in the United States.

Although most people in the developed world think of leprosy as a problem of the extreme past, it is surprisingly prevalent. Leprosy rates have been going down, thanks to efficient treatment options and early diagnosis, but there were still around 200,000 cases in 2010. Only about one hundred and fifty of them were in the United States. While most of those cases involve people who had just been abroad in areas with high rates of leprosy, some of them were indigenous to the US. Those cases seemed to be grouped around the American south.

Leprosy is disease caused by a bacterial infection. The bacteria in question, Mycobacterium leprae, affect the skin, the peripheral nervous system, the respiratory system, and the eyes. As they eat away, they cause major tissue damage. Although leprosy is a spectre that has frightened many populations so long that they forcibly segregated sufferers in colonies, it's hard to pass on. It is caught by contact with drops from the nose and mouth. Although the bacteria do attack the respiratory tract, leading to coughing, it's usually only transmitted through prolonged contact. Once it is picked up, it has a long incubation period, and can take up to twenty years to 'show'. When it finally does show up, it's easily and efficiently treated through a combination of three different drugs, called MDT or multi-drug therapy.

Which doesn't mean anyone wants leprosy showing up in their back yard. Louisiana State University and the Global Health Institute teamed up to see what could be found out about the mysterious American cases. They knew that armadillos could carry strains of leprosy - a result of their contact with colonists hundreds of years ago - but they didn't know whether or not the strain could be passed to humans. DNA analysis showed that the strain found in the creatures was identical to the one found in most of the humans who had come down with leprosy without having left the country. Since the contact has to be extreme, often the bacteria are only transmitted through the hunting and eating of armadillo meat.

Although the result is enough for officials to warn people off of eating or touching armadillos, there is no reason to worry about rampant leprosy infection. One of the reasons why armadillos are carriers is their low body temperature. The bacteria can't survive high temperatures, which is one of the reasons why they attack only human extremities. They're only comfortable around 86-89 degrees, and can't survive the hot inner-body temperatures. Researchers also think that the armadillo's immune system is deficient in some way. About ninety percent of humans who have contact with the disease have immune systems which fight it off without the person ever knowing they were sick. Still, swearing off armadillo burgers would be the best way to play it absolutely safe.

Image: Whaldener Endo

Via World Health Organization twice, and The New England Journal of Medicine. (Probable Zoonotic Leprosy in the Southern United States)