Fight against Leprosy: Some improvements, but why is it so difficult?

Abstract

Leprosy, due to Mycobacterium leprae infection, is an old transmissible disease, still unknown in many aspects. Although it is cured by a standardized multi-drug therapy, about 200,000 new cases are reported annually without marked decrease in incidence. This might be due to several problems. Antimicrobial resistance was recently measured at about 10%, but it is not routinely determined since M. leprae does not grow in vitro and molecular detection of resistance is the only tool available, usually not done in endemic countries. Although genome sequencing was achieved in 2001, leprosy appears as a disease neglected by researchers, stakeholders, professionals, and governments. Transmission routes and physiopathology are still mainly unknown in 2023. The WHO systematic review, conducted in 2018, concluded that there were still no biological diagnostic tests neither for the leprosy disease nor the M. leprae infection. The immune response is not elucidated, although it is fundamental for explaining the clinical forms of leprosy and the leprosy reactions that cause the nerve damage and sequelÆ. Fortunately, BCG vaccine gives some protection also for leprosy, because there are no specific vaccines available so far. Recently, M. lepromatosis was also involved in leprosy and M. leprae was found in wild animals. “Zero leprosy” is the new objective of WHO and non-governmental organizations. It seems optimistic since (i) governments are not significantly improving health access leading to delayed diagnostic of leprosy cases with disabilities, (ii) some others refuse to annul the stigma laws discriminating leprosy patients, (iii) companies and industrials do not produce diagnostic tests and promote new treatments, (iv) institutional funding agencies do not grant research on leprosy.