Leprosy and Parasitic Coinfections

Mycobacterium leprae and Mycobacterium lepromatosis are obligatory intracellular microorganisms that cause a disease called leprosy, one of the oldest known human diseases. The bacilli have adapted so well to the human cell due to the fact that they only need a minimal number of their own genes to survive, as their genome has become extremely short. As a result, currently, most people are genetically resistant to the disease and the bacilli do not enter their body or survive and then multiply in human’s body. In these people, it is believed that the bacillus cannot manipulate the host cell to its own advantage to create a suitable environment for survival (1). Only about 20% of the population is susceptible to leprosy, an estimate based on serology, epidemiological data, and the influence of immunosuppression (HIV) (2,3). The common belief in the past was that the adaptive cell-mediated immune system (CMI) was responsible for resistance to leprosy. However, some are now of the opinion that the CMI only contributes for this 20% to the resistance and determines the clinical image and the damage.