**Abstract**

Leprosy is a chronic infective disease that originates from the presence of pathogen agent *Mycobacterium leprae*. *Mycobacterium leprae* was discovered by the Norwegian doctor Gerhard Henrik Armauer Hansen in 1873. For the zoonotic transmission of M. leprae in the US the responsible insects are armadillos (*Dasypus novemcinctus*). M. leprae is an intracellular microorganism leading to loss of sensibility, innervation, intraepidermal impairment and lesions due to the absence of myelin in Schwann cells. *Mycobacterium leprae* has high infectivity and low pathogenicity. Incubation period is from 2 to 7 years. Leprosy is an infectious neurodegenerative disorder of the peripheral nervous system. Leprosy is the major cause of human disability due to neurological damage. Leprosy still represents one of the major causes of disabilities in humans. The most common complications are muscle weakness leading to atrophy, bone loss, amputations and blindness. In the case of chronic cutaneous hyperalgesia, there is a local increase in NGF levels. The application of anti-NGF antibodies may be of benefit in treating hyperalgesia in patients with neuropathy and impaired nerve endings. If combined, NGF, NT-3 and glial cell-line derived neurotrophic factor may be sustainable. In over 90% of human individuals an overall genetic resistance has been noted.

**Keywords:** *Mycobacterium leprae*, diagnosis, epidemiology, treatment, adult, children

### **1. Introduction**

Leprosy is a chronic infective disease that originates from the presence of pathogen agent *Mycobacterium leprae*. *Mycobacterium leprae* was discovered by the Norwegian doctor Gerhard Henrik Armauer Hansen (**Figure 1**) in 1873 as the first proof that a person's disease is caused by bacteria [1].

For the zoonotic transmission of M. leprae in the US the responsible insects are armadillos (*Dasypus novemcinctus*).

Since ancient times, leprosy has been considered as one of the first major human epidemic diseases.

The first noted leprosy epidemic was in Europe in 1873 due to the detection of *Mycobacterium leprae* in Norway (Bergen).

These regions included the Iberian Peninsula, Sicily, the Balkans, southern Romania, the Baltics, and Scandinavia. In Norway in particular, scientists investigated the disease known as "Spedalsked", the Norwegian name for leprosy [1].

In 2015, the number of newly diagnosed cases of leprosy was 210,758 worldwide (**Figure 2**).

**Figure 1.** *Gerhard Henrik Armauer Hansen.*

**159**

*Leprosy in the Modern Era*

0.3/10,000.

from 2 to 7 years.

damage.

quence of leprosy.

product) 9.5.

*DOI: http://dx.doi.org/10.5772/intechopen.91450*

individual with a high-bacterial load.

**2. History and epidemiology**

grouped in parallel or arranged in parallel.

disease is quite prolonged (2–5 years).

progression of neural lesions (**Figure 3**).

relation with deficient thermal sensation [3].

ations, muscle atrophy and bone resorption occur.

**3. Basic scientific considerations and pathology**

Transmission of leprosy persists despite efforts made by the World Health Organization (WHO). With the highest incidence in India, Brazil and Indonesia. *Mycobacterium leprae* is a non-motile, acid-fast pathogen and cannot be cultured on any known medium. The most common route of transmission in humans may be via nasal droplets. Predisposing factor may be a prolonged contact with an infected

Leprosy still represents one of the major causes of disabilities in humans. It has

M. leprae is an intracellular microorganism and an acid-resistant bacilli leading to a loss of sensibility, innervation, intraepidermal impairment and lesions due to the absence of myelin in Schwann cells. If the bacilli are numerous, they can be

M. leprae has high infectivity and low pathogenicity. The incubation period is

An individual is infected by inhalation of infectious aerosol or through the skin while contacting with nasal secretions and/or skin changes of the infected individual. Children are more susceptible to leprosy than adults. Due to the slow proliferation of leprosy (the time of one generation is 14 days), the incubation period of the

Due to infiltration of the peripheral nerves, neuritis, anesthesia, trophic ulcer-

Leprosy is an infectious neurodegenerative disorder of the peripheral nervous system. Thus, leprosy is the major cause of human disability due to neurological

In the process of leprosy-associated neuropathy, the presence of bacilli in nerve endings and Schwann cells induces a response mediated by macrophages and other

The most important cytokines are TNF-α, IL-6, IL-17 that are involved in the

TrkA receptors are detected in subepidermal fibers. TrkA receptor messenger RNA is produced in the skin. NGF are also present in keratinocytes and are in cor-

NGF levels are depleted in nerve and skin lesions in leprosy the loss of NGFdependent nociceptive fibers in damaged skin. An additional cause of decreased NGF is an impaired interaction between keratinocytes and nerves in affected skin.

According to Antunes et al., it was concluded that in the individuals with neuritic leprosy, NGF-R immunoexpression was lower (nerve fiber, Schwann cells) than in control group (normal individuals). In the leprosy group, hypoesthesia was associated with decreased expression of NGF-R and PGP (protein gene

To this date, M. leprae has not been cultivated on artificial nutrients. Nerve injury-associated tissue damage is the most prominent clinical conse-

cells that eventually leads to the appearance of immune-mediated lesions.

Based on 193, 118 cases at the end of 2017, prevalence rate corresponds to

been estimated that approximately 3 million individuals are affected.

**Figure 2.**

*Newly diagnosed cases of leprosy worldwide [2].*

#### *Leprosy in the Modern Era DOI: http://dx.doi.org/10.5772/intechopen.91450*

*Pathogenic Bacteria*

**158**

**Figure 2.**

**Figure 1.**

*Gerhard Henrik Armauer Hansen.*

*Newly diagnosed cases of leprosy worldwide [2].*

Transmission of leprosy persists despite efforts made by the World Health Organization (WHO). With the highest incidence in India, Brazil and Indonesia.

*Mycobacterium leprae* is a non-motile, acid-fast pathogen and cannot be cultured on any known medium. The most common route of transmission in humans may be via nasal droplets. Predisposing factor may be a prolonged contact with an infected individual with a high-bacterial load.

Leprosy still represents one of the major causes of disabilities in humans. It has been estimated that approximately 3 million individuals are affected.

Based on 193, 118 cases at the end of 2017, prevalence rate corresponds to 0.3/10,000.
