Ecology and Epidemiology Aspects of Mycobacterium leprae
Leprosy is a chronic infectious disease also known as Hansen’s disease, caused by Mycobacterium leprae that tends to be chronic and to compromise human societies by producing peripheral nerve damage, limb loss, blindness, and disfiguring skin lesions. Leprosy occupies a prominent position among infectious diseases due to its high frequency of disability and associated stigma. Detection of grade 2 disability (G2D) reflects a delay in the diagnosis of leprosy, which results in persistent neuritis leading to disability. There is also a possibility that there might be hidden cases in the population. Mycobacterium leprae has been reported for than 2000 years and today they are ubiquitous, occurring in every habitat and ecosystem of the world, perhaps except for the polar- regions. The first known representative of this group was discovered, under the name of Bacillus leprae, by Hansen in 1875. M. leprae is a non-cultivable obligate intracellular pathogen with a slow division time that targets peripheral nerves by predominantly infecting Schwann cells and histiocytes and keratinocytes in the skin. Leprosy is classified according to the WHO guidelines in 2012 to Paucibacillary leprosy (PB) and Multibacillary (MB).Up to 95% of patients exposed to M. leprae will not develop the disease, suggesting that host immunity plays an important role in disease progression and control. The incubation time is variable, ranging from 2 to 20 years, or longer cases have been reported supporting the possibility of transmission by different ways, and discussions on different ways of transmission are continuing. Today the prevalence of this ancient disease is declining in most around the world this decline is a direct effect of widespread administration by public health workers of multidrug therapy. However, emerging despite the use of multidrug therapy, identifying and monitoring resistance are still necessary.