Mo Costandi describes a paper with a really fascinating finding about the workings of leprosy: "Leprosy spreads by reprogramming nerve cells into migratory stem cells".
Anura Rambukkana of the MRC Centre for Regenerative Medicine at the University of Edinburgh and his colleagues isolated Schwann cells from adult mice, grew them in Petri dishes and infected them with M. leprae. They found that the bacterium gradually turns off the genes that give Schwann cells their characteristic properties, and then activates another set of genes that transforms them into something resembling neural crest stem cells, which are only present in the embryo, and which migrate from the developing nervous along various routes to form a wide variety of tissues, including muscle, bone, cartilage, and the Schwann cells and sensory neurons of the peripheral nerves.
On a scale of how parasites and pathogens manipulate our biological pathways to achieve their own ends, this one runs pretty deep. Exploiting our mechanisms of embryonic development to migrate through the body inside our own cells. Leprosy may be one of the oldest human pathogens, with its long slow course really well suited to spreading in small human communities with infrequent contacts among groups.