Commentary: Leprosy and poverty

A hundred years ago the hot debate in leprosy circles revolved around disease causation; was leprosy hereditary or could the bacterial hypothesis of Armauer Hansen be believed? These arguments had important and very different public health consequences. If hereditary then patients should be stopped from reproducing but did not need isolation and confinement. However if a bacterial aetiology was believed then leprosy patients should be isolated from society to prevent spread of infectious organisms. At that time there were no effective antibiotics for treating leprosy. We still have an imperfect understanding of the transmission and causation of leprosy and the importance of various factors in disease causation still influence public health policy. The study in this issue of the International Journal of Epidemiology by Kerr-Pontes et al. showing an association between poverty and leprosy is an important new contribution to today’s debate. Leprosy is caused by Mycobacterium leprae and has a long incubation period ranging from 5 to 15 years. Patients with lepromatous leprosy shed mycobacteria in their nasal secretions thereby continuing infection. M. leprae is a hardy organism and can survive for up to 5 months in India. Molecular techniques have shown that in endemic areas up to 5% of the population are carrying M. leprae DNA in their noses. Leprosy has an uneven geographical spread; 85% of the world’s patients live in six countries (India Brazil Nepal Myanmar Mozambique and Madagascar). Even in low endemic countries such as South Africa certain regions are identified with new leprosy cases. (excerpt)