Causes of leprosy
Last reviewed: 23.04.2024
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The causative agent of human leprosy - Mycobacterium leprae (M. Leprae hominis, M. Hanseni), described in 1874 by G. Hansen, belongs to the genus Mycobacterium.
Morphology of the causative agent of leprosy has been studied on fixed preparations in light and electron microscopes. A typical form of mycobacteria leprosy is straight or slightly curved sticks with rounded ends, from 1 to 4-7 microns in length and 0.2-0.5 microns in width. Grain, branched, and other forms of the pathogen are also observed. They are immovable, spores and capsules do not form, acid and alcohol resistant, Gram-positive, stained according to Tsil-Nielsen in red. They are intra- and extracellular, they tend to group together, being parallel to each other ("cigarette packs"). They can be in the form of globular clusters (globi), with a diameter of 10-100 microns, and sometimes - about 200 microns. According to morphology, tinctorial and antigenic properties, the causative agent of human leprosy has a great similarity with mycobacterium tuberculosis.
Mycobacterium leprosy is an obligate intracellular parasite localized in the cytoplasm of the cells of the reticuloendothelial system and tissue macrophages. Has a tropism for the skin and peripheral nerves. It reproduces by dividing the mother cell into two daughter cells by ingrowing the transverse septum. The pure culture of the pathogen is not obtained, as mycobacteria leprosy do not grow on nutrient media. Only after C. Shepard (I960) developed a method of experimental infection of human leprosy laboratory mice, and W. Kirchheimer and E. Storrs (1971) - nine patchy armadillo (Dasypus novemcinctus Linn.), There was the possibility of a broader study of biology, the biochemistry of mycobacterium leprosy , obtaining diagnostic and vaccine preparations, testing new drugs, determining the drug resistance of the causative agent of leprosy. There are reports of susceptibility to mycobacteria of human leprosy as well as a seven-battled battleship, a Korean chipmunk and turtles.
[Epidemiology of leprosy
Leprosy is still common in many countries. Its endemic foci are found in Asia, Africa, South and Central America, and Europe, mainly in countries with low levels of material support, general and sanitary culture. At present, the number of leprosy patients on the globe is 10-15 million. The total exponent of its spread is 1.33 per 1000 population.
Traditionally, it is believed that the only reservoir and source of infection leprosy is a sick person. The most contagious are patients with lepromatous and borderline leprosy. However, recently data have been obtained indicating that a number of species of animals can be a reservoir of mycobacteria leprosy: a nine-battled battleship, chimpanzees, some other types of monkeys and some species of arthropods. Their possible role in the transmission of leprosy to a person is studied. The main route of infection is airborne (through the mucous membranes). It is possible to contaminate leprosy through damaged skin and bloodsucking insects. Vertical transmission of infection is not observed: in leprosy patients, children are born healthy.
Adults are relatively resistant to leprosy. Of the people who had been in contact with patients for a long time, about 10-12% were ill. Cases of professional infection leprosy, according to foreign literature, were single. Children are more susceptible to a leprosy infection. In most cases, infection with leprosy occurs in early childhood with prolonged and constant contact of the child with a sick leprosy. The incidence of men and women is the same.