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What causes toxoplasmosis?
Last reviewed: 20.11.2021
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Causes of toxoplasmosis
The causative agent of the disease - Toxoplasma gondii - belongs to the class of sporoviks, the order of coccidia, the genus of toxoplasm - obligate intracellular parasites.
In the form of toxoplasma reminiscent of the orange slice or crescent moon. They are bent, one end is pointed, the other is more round in size (4-7) x (2-5) μm. When painting according to Romanovsky-Giemsa, the parasite is dyed blue, and the nucleus is ruby-red.
Toxoplasma - intracellular parasites (endozoites) that can reproduce asexually (schizogony) in cells of various tissues (liver, placenta, CNS, etc.) of many species of warm-blooded animals, as well as humans.
In the process of reproduction, clusters of toxoplasm are formed inside the cells, called pseudocysts at this stage of development, since, unlike cysts, they do not have their own envelope. When the disease passes into a chronic form, true cysts (cystozoites or bradizoites) form from pseudocysts.
The sex cycle of reproduction of toxoplasm occurs in the epithelium of the intestine of the final host, such as the domestic cat and some other members of the cat family.
Pathogenesis of toxoplasmosis
From the entrance gates (gastrointestinal tract), toxoplasma with lymph flow enters the regional lymph nodes, where they multiply, causing inflammatory changes with the formation of an infectious granuloma. Clinically, this can be manifested by mesadenitis. Having reached a certain concentration, the parasites penetrate into large amounts into the blood and are carried throughout the body, affecting the liver, spleen, nervous system, myocardium, skeletal muscles, the membranes of the eye and other organs and tissues. Active proliferation of toxoplasm is accompanied by the release of various toxins and allergens leading to delayed-type hypersensitivity. With the formation of immunity, the reproduction of toxoplasm slows down, eventually the vegetative forms (endocytes) disappear in the blood and internal organs and cysts begin to form, which can persist in the body throughout life.
In most cases (95-99%) infection with toxoplasma does not lead to the development of manifest forms of the disease, but immediately forms a latent infection with delayed-type hypersensitivity to toxoplasmin and the production of humoral antibodies. Clinically, such forms are not manifested in any way, the person remains healthy, although in the initial period of a latent disease occurs dissemination of toxoplasm throughout the body. If this period coincides with pregnancy, the probability of infection of the fetus is high.