Causes and pathogenesis of tularemia
Last reviewed: 23.04.2024
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Causes of tularemia
The causative agent of tularemia is Francisella tularensis, a small (0.2-0.5 micron) immobile gram-negative rod, grows well under aerobic conditions on nutrient media with the addition of cysteine, glucose and blood products.
Pathogenesis of tularemia
The causative agent enters the body through the skin or mucous membranes of the eyes, respiratory tract, GIT. At the site of the pathogen introduction, a primary affect often occurs in the form of ulcerative necrotic defect and regional lymphadenitis. With the breakthrough of the lymphatic barrier, the pathogen and its toxins enter the bloodstream, which signifies the emergence of bacteremia and generalization of the process, as a result of which metastasis of the infection with the formation of secondary tularemia buboes and damage to internal organs is possible.
Epidemiology
Tularemia is a typical natural focal zoonotic infection. In natural foci the main source of infection is rodents: water rats and mice. The infection of many domestic animals, as well as various parasitic ticks and insects has been established. A sick person as a source of infection with tularemia does not play a role.
Transmission of infection among animals is carried out mainly bloodsucking arthropods: mites, mosquitoes, fleas, etc. Ways of human infection:
- contact - in contact with sick or fallen animals, with environmental objects, contaminated with rodent secretions;
- alimentary - when eating food and water contaminated with secretions of infected rodents;
- airborne - by inhalation of infected dust;
- transmissible - with bites of ticks, mosquitoes, flies, gnats, etc. Children are usually infected by a transmissible and alimentary route. Disease
Are met almost exclusively in rural areas, individual cases are recorded on the outskirts of cities closely adjacent to the name-marsh foci of tularemia. In the conditions of the city, children can get sick from contact with domestic animals, especially with the corpses of dead rodents, as well as when leaving their parents for the city. Sporadic cases are usually noted, but epidemic outbreaks among children in pioneer camps close to natural foci of infection are also possible. Susceptibility to tularemia, apparently, is universal. The patients who are ill receive stable immunity lasting not less than 10-15 years.
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