Protozoa parasites

The protozoa type (Protozoa) includes more than 15, 000 species of animals that live in the seas, freshwaters and soils. In addition to free-living forms, a number of parasitic forms are known that can sometimes cause serious diseases, such as protozoanosis.

The body of a protozoan consists of only one cell. The body shape of protozoa is varied. It can be permanent, radial, bilaterally symmetrical (flagellates, cilia), or have no permanent shape at all (amoeba). The body size of protozoa is usually small - from 2 to 4 microns to 1. 5 mm, although some large individuals reach 5 mm and fossil shell rhizomes are 3 cm or larger in diameter.

the simplest human parasites

The body of the protozoa consists of the cytoplasm and the nucleus. The cytoplasm is bounded by the outer cytoplasmic membrane and contains organelles - mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus. Protozoa have one or more nuclei. The form of nuclear division is mitosis. There is also a sexual process. It consists of the formation of a zygote.

The locomotor organs of protozoa are flagella, cilia, jaws; or not at all. Most protozoa, like all other members of the animal kingdom, are heterotrophic. However, there are autotrophs among them.

The most easily tolerated adverse environmental condition is the ability to encystate, i. e. they form a cyst. With the formation of the cyst, the locomotor organs disappear, the volume of the animal decreases, it becomes rounded, and the cell is covered with a dense membrane. The animal becomes dormant and returns to active life under favorable conditions.

Encysting is a tool that not only protects but also spreads parasites. Some protozoa (sporozoa) form an oocyst and in the process of reproduction a sporocyst.

The proliferation of protozoa is very diverse, from simple division (asexual reproduction - approx. Biofile. Ru) to a rather complex sexual process - conjugation and mating.

The habitat of the simplest is varied - it is the sea, fresh water, moist soil. Parasitism is widespread. Many parasitic protozoan species cause serious diseases in humans, domestic and wild animals, and plants.

Protozoa are able to move and respond to various stimuli (phototaxis, chemotaxis, thermotaxis, etc. ) using pseudopods, flagella, or cilia. Protozoa feed on the smallest animals, plant organisms, and decomposing organic matter, and parasitic forms live on the surface of the body, in the body cavities or tissues of their hosts.

The pathways of food uptake into the cell body are also different: pinocytosis, phagocytosis, osmotic pathway, active transport of substances across the membrane. The resulting food is digested in digestive cavities filled with digestive enzymes. Some photosynthetic intracellular symbionts, such as chlorella or chloroplasts (such as euglena), are able to synthesize organic matter from inorganic materials by photosynthesis.


Toxoplasmosis (Greek: toxon arc, arc) refers to diseases caused by the simplest unicellular organisms in the various parts of the human body where they have been introduced and multiplied. The pathogen of toxoplasmosis - Toxoplasma Toxoplasma gondii belongs to the genus of protozoa, the class of flagellates.

The toxoplasma is crescent-shaped and resembles an orange slice: one end of the parasite is usually pointed and the other is rounded, up to 7 microns in length. The toxoplasma moves with a slip. They penetrate the cells by rotating around the longitudinal axis.

Toxoplasma is propagated by asexual, longitudinal bisection. Repeated longitudinal division in the protoplasm of the host cell results in the accumulation of daughter parasites called "pseudocysts. "False cysts are found in large numbers in various organs of the infected organism in the acute stage of the infection. They are surrounded by a very obscure membrane, apparently made up by the host cell, and have no membrane of their own. Cells full of such parasites are killed. The released parasites invade new cells where they redistribute and form new pseudocysts.

When the infection becomes a chronic form, the Toxoplasma remains in the form of real cysts (surrounded by a special shell). Such cysts are able to persist in the body of animals and humans for a long time (up to 5 years). Cysts can also be found in the tissues of the eye, heart, lungs, and some other organs. The number of Toxoplasma in a cyst ranges from a few specimens to thousands.


Giardia is the simplest parasitic animal in the flagellate class. Pear-shaped, 10-20 µm long; the dorsal side is convex, the ventral side is concave, and forms an adhesive disc that temporarily adheres to the intestinal epithelial cells of the host. 2 oval seeds, 4 pairs of flagella. It lives in the human gut (especially in children), especially in the duodenum, less commonly in the bile duct and gallbladder, and causes giardiasis. Asymptomatic parasite carriers are common. Infection with cysts occurs when protozoa enter the lower intestine through the mouth, when contaminated food or water enters the body, and with dirty hands, and so on. The incidence is sporadic. Giardiasis is common in all parts of the world.

The pathogen of the disease is lamblia - (Lamblia intestinalis). Giardia is a single-celled microscopic parasite. Giardia can withstand freezing and heating up to 50 ° C, but dies when boiled. In the United States, giardiasis is the leading parasitic gastrointestinal disease. According to the INTERNET, giardiasis affects up to 20% of the world's population. Infection can occur if we drink unboiled tap water or ice made from such water, when we wash vegetables and fruits with unboiled water. Swimming in open water bodies and pools infested with lamblia cysts carries a high risk of disease. A newborn can become infected during labor during a head fracture and birth. The route of contact household infection is less common, but with the high prevalence of the disease, this is already becoming quite real, especially among segments of the population with poor general hygiene skills.


Trichomonas vaginal cysts are not formed and are fed by bacteria and erythrocytes. Causes inflammation of the urogenital system - trichomoniasis. The causative agent of the disease is sexually transmitted. Non-sexually transmitted infections (through a toilet, bed, etc. shared with the patient) are less common. It can also be passed from a sick mother to a newborn girl. The transition to a chronic form of the disease is possible. It is difficult to handle as it spreads to the appendices. In trichomoniasis, the vagina is most often affected with abundant purulent discharge with an unpleasant odor; itching and burning sensation can be felt in the vagina. In men, the symptom is urethritis, which is accompanied only by small mucosal secretions.


The amoeba lives in freshwater. The shape of the body is volatile. Performs very slow (13 mm / h) movements. It moves with the help of jaws, the body flows from one part to the other: either shrinking into a round knot or spreading the "tongue legs" to the side.

Pseudopods are also used to capture food. During nutrition, the body particles of amoeba flow around the food particles from all sides and enter the cytoplasm. Digestive flash appears. This diet is called fabitosis. The food consists of bacteria, unicellular algae, small protozoa. Substances released from the environment are absorbed by pinocytosis.

There is a contractile or pulsating vacuum in the body of the amoeba. Its function is to regulate the osmotic pressure in the body of the protozoan. Reproduction is asexual, with mitosis and then splitting the body of the amoeba. Of great importance in medicine are the amoebas of the genus Entamoeba, which live in the human digestive system. These include dysentery or histolytic amoeba.

Plasma malaria

Plasmodium malaria causes malaria, which is associated with febrile seizures, blood changes, and enlargement of the liver and spleen. There are four forms of malaria: three-day, four-day, tropical, and oval malaria. The source of the disease is a malaria person and the carrier is a female malaria mosquito. The female mosquito, which becomes infected while the patient is sucking blood, becomes capable of transmitting plasmodium. A healthy person is infected by the bite of a mosquito infected with a plasmodia, through which the pathogens enter the body through saliva. With blood flow, plasma modes enter the liver, where they go through the first (tissue) developmental cycle, then into the bloodstream and invade the red blood cells. This completes the second (erythrocyte) developmental cycle, which ends with the breakdown of red blood cells and the entry of pathogens into the patient’s blood, accompanied by a fever attack.