Leprosy, otherwise known as Hansen’s disease, can be caused by 2 distinct bacteria; Mycobacterium leprae and Mycobacterium lepromatosis, the latter being a fairly new discovery made only in 2008.
It is not entirely clear how leprosy is transmitted, however, it is generally believed to be via close contact and through nasal droplets. The primary sign of leprosy are light or dark skin lesions over the body. If left untreated, this can worsen into permanent damage to eyes, nerves, skin and limbs. Secondary infections can cause the loss of tissue, resulting in shortened and deformed extremities.
The incubation period of the 2 species can range from 9 months to 20 years as the bacteria replicates within white blood cells and nerve cells. The 2 species lack genes needed for them to survive outside their hosts and M. leprae has the longest doubling time of any known bacteria making it difficult to study using traditional culturing methods.
Despite this, a treatment for leprosy is available using multidrug therapy (MDT). MDT contains rifampicin, clofazimine and dapsone. It is extremely effective and most patients are usually not infectious after the first monthly dose.