Toxoplasmosis
AUTHORS : Yankova L.B.
RELEVANT UNIVERSITIES : Center “IMEDIS”, Moscow, Russia
YEAR : 2004 | Category : Educational
Toxoplasmosis is a widespread disease that is most dangerous for expectant mothers. The causative agent of toxoplasmosis Toxoplasma gondii is the simplest of the sporozoea class, an intracellular parasite. Morphologically similar to an orange slice with one rounded end 4–7 μm long. The life cycle consists of two stages of reproduction. The first stage is sexual. The primary and main hosts are domestic cats and other felines, in the body of which sexual reproduction of the pathogen occurs.
Primary damage to cats occurs when rodents containing oocysts are eaten, from which parasites (sporozoites) emerge and penetrate the intestinal cells, where they are converted into trophozoids. Trophozoids reproduce asexually (schizogony). Sexual reproduction takes place in the cells of the intestinal mucosa. The merozoites formed as a result of asexual reproduction destroy epithelial cells and penetrate into the underlying layers of the intestinal wall, where they are transformed into gametocytes.
The fusion of heterosexual gametocytes leads to the formation of a zygote (oocyst). Oocysts are rounded formations with a dense, colorless 2-layer membrane of 9-14 microns. They are excreted from the body of cats with feces and persist for a long time (up to two years) in the external environment – soil, children’s sandboxes. Mammals and rodents become infected by ingesting oocysts. The entire reproduction cycle in the body of the final owner (cat) takes 1-3 weeks.
Many infected animals and birds become intermediate hosts of toxoplasmosis. A person becomes infected when eating insufficiently thermally processed meat of these animals. The body goes through an asexual cycle of development and reproduction. From the oocysts that have entered the body, parasites emerge, which are actively absorbed by macrophages. Phagocytosis is incomplete. The causative agent (sporozoids) dissimilate along the lymphatic vessels with macrophages.
