Tuberculosis is a chronic infectious disease caused by MBT. It is characterized by a primary chronic undulating course, multiple organ damage and a variety of clinical manifestations. The most frequently affected organs are the respiratory organs. Tuberculosis is the most widespread infectious disease in the world and in Russia.
The causative agents of TB are mycobacteria of the human species (M. tuberculosis), bovine species (M. bovis) and intermediate species (M. africanum). Mycobacteria of the human species most often (in 92% of cases) are the causative agents of tuberculosis in humans, while mycobacteria of the bovine species and intermediate species are responsible for 5% and 3% of cases, respectively.
The source of causative agents of infection is a person with tuberculosis, as well as diseased animals (especially cattle).
The most common route of infection through the upper respiratory tract is aerogenic — 93% (airborne, dust). Mycobacteria can enter the body through the alimentary route (with milk, sour cream, cottage cheese, etc.), by contact — through the damaged surface of the skin and mucous membranes.
Pathomorphological changes. Inflammation develops on an immune basis due to delayed-type hypersensitivity (DST) and is productive. Mycobacteria typically induce specific changes in conjunction with non-specific ones in most forms.
At the heart of a specific lesion is a granuloma (tuberculous tubercle). Morphologically, it is an epithelioid-giant-cell granuloma with an area of caseous necrosis. MBT is an intracellular infection. A specific granuloma forms in 6–8 weeks.
TB pathogenesis is complex and depends on many conditions, in which the infectious agent (mycobacterium) and the macroorganism interact.
There are 2 stages of tuberculosis infection: primary and secondary.
The primary period is marked by the development of tuberculosis in an organism that is still intact. The most important are massiveness and virulence of the infection. The fact of infection is established, as a rule, by the «conversion» of the Mantoux tuberculin test, i.e., the appearance of a positive infectious test for the first time and corresponds to the appearance of a specific immune response. Before the appearance of an immune response, the stage of bacteremia is observed from 4 to 8 weeks. The primary period has a tendency to spontaneous healing with varying degrees of severity of residual changes.
Characteristics of tuberculosis during the primary stage:
- infection of an intact organism (contact with a bacterial excretor is required);
- hypersensitivity to mycobacteria and tuberculin;
- «conversion» of the tuberculin test;
- lymphotropism;
- the presence of paraspecific changes (enlarged lymph nodes, erythema, conjunctivitis, etc.);
- young age (mainly children and adolescents);
- the disease manifests as a condition affecting the entire body (functional disorders);
- a tendency to spontaneous recovery, the formation of specific immunity.
After infection, the primary period may end in infection or disease (local or non-local forms). The primary period includes 3 forms — intoxication (11%), primary tuberculosis complex (10%), tuberculosis of the intrathoracic lymph nodes (60–80%). The remaining pulmonary forms belong to the secondary period.
Extrapulmonary forms have a secondary origin. In the structure of forms, they make up to 17%. The most common extrapulmonary forms are kidney tuberculosis, osteoarticular tuberculosis, tuberculosis of the peripheral lymph nodes.
The secondary period of tuberculosis develops against the background of a previous infection at a more mature age, as a result of the reactivation of post-primary residual changes in the intrathoracic lymph nodes, lungs and other organs. Various debilitating factors play a decisive role in the pathogenesis of secondary forms. There may be exogenous re-infection. The disease takes on the character of a local lesion.
The role of the general practitioner is to prevent TB in the family members under their care and to prevent the spread of the infection within the family.
The goal is solved by the following TASKS:
- preventing the entry of TB patients into the family;
- active early and timely detection of tuberculosis in family members;
- identification and monitoring of high-risk groups for tuberculosis in the family;
- creating immunity to tuberculosis in uninfected family members;
- carrying out preventive measures for tuberculosis (together with a phthisiatrician);
- sanitary and educational work on the prevention of tuberculosis;
- timely and full implementation of anti-epidemic measures in the family when a patient with active tuberculosis is detected.