INFECTIOUS AGENTS: Gerhard Armauer Hansen observed Mycobacterium leprae for the first time in infected nodules excised from leprosy patients. Barely distinct, rod-shaped bacteria (purple) became apparent under Hansen’s microscope. However, it took German bacteriologist Albert Neisser’s stain for the bacterium, developed after visiting Hansen in 1879, to make M. leprae clearly visible. Pictured are illustrations of M. leprae-infected cells from a testicle, taken from Hansen’s 1895 book Leprosy: In its Clinical and Pathological Aspects.WELLCOME LIBRARY, LONDONNorwegian physician Gerhard Armauer Hansen first saw rod-shaped microbes in samples harvested from leprosy patients in 1873. Seven years later, Hansen, who worked in the leprosy hospital in the coastal town of Bergen, was on trial for attempting to infect a patient with bacteria without permission, using a cataract knife to inoculate a woman’s eye with material from leprous lesions.
Hansen resorted to such an extreme measure because he was having trouble proving his conviction that the microbes caused leprosy—which results in peripheral nerve damage and skin lesions—and that the disease was infectious. He had tried in vain to infect rabbits and to cultivate the microbe in vitro—evidence considered necessary to prove contagiousness. “Leprosy was afterwards called the least contagious of contagious diseases,” says Tony Gould, author of A Disease Apart: Leprosy in the Modern World, which might explain why Hansen had struggled to come up with the necessary proof.
Hansen’s unfortunate patient, a 33-year-old woman named Kari Nielsdatter, already had tuberculoid leprosy, one form of the disease, but Hansen hoped to infect her with a second form, called lepromatous leprosy. The infection did not ...
