Causes of anthrax

Causes of anthrax

The cause of the anthrax is a large Gram-positive immobile stick of Bacillus anthracis of the genus Bacillus of the Bacillaceae family, an aerobic or facultative anaerobic. It grows on simple nutrient media, with the access of free oxygen forms spores. Under favorable conditions (getting into a living organism) forms a vegetative form. The causative agent contains two capsular polypeptide and one somatic polysaccharide antigens. Produces exotoxin, consisting of protein and lipoprotein, includes a protective antigen. It interacts with cell membranes and mediates the action of other components: a lethal factor that has a cytotoxic effect and causes pulmonary edema and an edema that causes an increase in the concentration of cAMP and the development of tissue edema. The toxin components cause toxic effects only when combined. The pathogenicity of B. Anthracis depends on the presence of a capsule and toxin formation. Strains that do not possess these abilities are avirulent. The capsule plays an important role in the onset of the infectious process, preventing the phagocytosis of the pathogen. The toxin mediates the main clinical manifestations of the disease. The vegetative forms of the microbe are not very stable, they instantly die off during boiling, the disinfectant solutions kill them in a few minutes. In unopened corpses, the pathogen persists for 7 days. Spores are formed after the death of the host, they are extremely stable, can withstand boiling for up to 30 minutes, persist with rapid drying, freezing. Disinfectants (1% formalin solution, 10% solution of caustic sodium) kill them for 2 hours. In the soil they are able to persist for several decades (up to 60 years) and germinate both in contact with living organisms and in soil in the presence of favorable conditions.

[1], [2], [3], [4], [5], [6],

Anthrax pathogenesis

Infection occurs when both the vegetative form and the spores of the causative agent enter the human body, where they are protected from phagocytosis by the capsule and produce exotoxin, which causes damage to the vascular endothelium. Microcirculatory disorders and increased vascular permeability are an important link in the pathogenesis of anthrax. As a result of these changes in the breeding grounds of the pathogen (skin, lymph nodes, lungs, intestinal wall) develop serous-hemorrhagic inflammation, perivascular hemorrhages. Hemorrhagic infiltrates, sharp edema. When infected with aerosol and alimentary pathways, the pathogen easily overcomes the lymphatic barrier, spreads hematogenically. The infection takes a generalized character with massive seeding of organs (septicemia), accompanied by the development of infectious-toxic shock, thrombohemorrhagic syndrome and multiple organ failure. With percutaneous infection, general infection is rarely observed. Inflammation is limited to the skin, is local in nature, but toxins cause increased vascular permeability with the development of extensive edema and local anesthesia.

[7], [8], [9], [10], [11], [12]

Epidemiology of anthrax

The reservoir of infection is the soil in which, due to the repetition of biological cycles (spore-vegetative cell), the causative agent persists for a long time and accumulates. This feature of V. Anthracis contributes to the creation of long-term active soil foci ("damned" fields) and potentially hazardous areas. This leads to periodic epizootics and cases of anthrax in humans. The disease develops when the body enters vegetative cells or spores the pathogen. The sources of B. Anthracis for humans are large (buffaloes, cows) and small (goats, sheep) cattle, horses, camels, and (in rare cases) wild animals (rabbits, wolves, bears, arctic foxes, etc.). Sick animals excrete the pathogen with urine, feces and other secretions. The incidence of people depends on the extent of the spread of this infection among animals. Mechanisms of transmission of pathogens to humans - contact (in violation of personal hygiene rules for caring for animals, slaughtering and cutting carcasses, skinning, contact with wool, skins and other products of animal husbandry, contaminated with B. Anthracis), aspiration (airborne dust inhalation of infected dust, bone meal), fecal-oral (food route when eating meat of an infected animal) and transmissible (via bites of flies, flies, mosquitoes). Transmission factors - soil, water, air, food, household items, animals and their livelihoods, ectoparasites.

There are three types of incidence of anthrax: professional-agricultural, professional-industrial and household. The occupational and agricultural morbidity in countries with a temperate climate is recorded mainly in the livestock regions between May and October. The probability of the onset of the disease depends on the dose of the pathogen, the mode of infection and the factors of the resistance of the macroorganism. With the contact mechanism of transmission, a person is insensitive to the pathogen and infection is possible only if the integrity of the skin and mucous membranes is compromised. With air-dust and alimentary ways of infection, the susceptibility is almost 100%. Sick people do not pose a danger to others. Immunity in those who had recovered is unstable, there are cases of repeated diseases.

[13], [14], [15], [16], [17],