The bacilli affect skin, mucous membranes, peripheral nerves, eyes and internal organs, in some cases the lymph nodes. The incubation time of the disease can take up to 20 years and more. On average it takes 2-4 years for the symptoms to appear.
Leprosy occurs in several clinical manifestations. In general it is classified in tuberculoid leprosy (“paucibacillary”) and lepromatous leprosy (“multibacillary”). There is a wide spectrum of intermediate forms, also referred to as borderline leprosy.
Even if leprosy is thought to be eradicated in most of the countries, according to the WHO, we still had to face about 213.000 new cases worldwide at the beginning of 2009. An estimated 3 million people are suffering from long-term consequences. Until now preventative measures in form of immunization are not available.
The bacilli have never been cultured in vitro. The common diagnostic method is the detection of Mycobacterium leprae in skin smears. The microscopy allows the differentiation between paucibacillary (PB) leprosy (= smear-negative) and multibacillary (MB) leprosy (= smear-positive), which is an important information with regard to therapy.
Because experience in practical application of histology and/or molecular biology is required, these sensitive detection methods are mainly performed in reference laboratories. The same also applies for the drug susceptibility testing in mouse foot pads which is very labour- and time-consuming. On the basis of these facts, it is difficult to get reliable data about primary and secondary antibiotic resistance rates; thereby resistances to rifampicin and dapsone are described.
Now, a fast and reliable test system for the molecular genetic identification of M. leprae and its antibiotic resistances is available: The GenoType LepraeDRpermits the simultaneous detection of M. leprae and its resistance to rifampicin, ofloxacin and dapsone within a few hours.