Parasitic protozoa are single-celled animals that live off other organisms called hosts.
Sporozoans are unicellular organisms that lead an exclusively parasitic lifestyle. There are about 4 thousand of them. They parasitize the organisms of worms, insects, animals and humans.
Due to their parasitic lifestyle, sporozoans differ from other protozoa:
* Adult sporozoans do not have movement organelles.
* There are no digestive and contractile vacuoles, since nutrition is provided by the entire surface of the cell.
* Reproduction in most sporozoans is asexual. The parasite cell breaks down into many daughter cells – independent organisms.
In the human body, about 30 species of protozoa can parasitize. The most dangerous for humans is the malaria plasmodium – the causative agent of malaria.
The life cycle of the plasmodium malaria is complex and proceeds with a change of hosts: the malaria mosquito (genus Anopheles) is the main host; man is an intermediate master.
The main host is an organism, inside which the parasite reproduces sexually.
An intermediate host is an organism within which the parasite reproduces asexually. One parasite may have several such hosts.
Asexual reproduction: when bitten by a female mosquito, parasites from the saliva of the mosquito enter the human blood and penetrate into the liver cells. Here they divide and, as a result, form forms that can settle in erythrocytes (red blood cells). In erythrocytes, plasmodium actively multiplies, and as a result, there are so many plasmodia that the blood cell bursts. Parasites enter the bloodstream and infect new cells. During the rupture of blood cells, a person has bouts of fever (high body temperature).
Sexual reproduction: while the female mosquito sucks the blood of a sick person, the plasmodium enters the mosquito’s digestive tract. There, sexual reproduction takes place, as a result of which individuals of the next (asexual) generation are formed. During the bite, they enter the human bloodstream, and the cycle repeats.