Everyone has heard about such a dangerous disease as malaria. But not everyone knows that its causative agent is the simplest microscopic animal - malarial plasmodium. You will learn about the life cycle, structural features and development of this organism from our article.
Features of the organization of Protozoa
Plasmodium is a representative of the most primitive group of animals - the unicellular or protozoan sub kingdoms. The following symptoms are characteristic of them:
- the body consists of one cell, which performs the functions of the whole organism;
- the presence of a core;
- lack of a dense cell wall;
- movement using specialized structures: cilia, pseudopods, flagella;
- the presence of digestive and contractile vacuoles ;
- gas exchange through the cell surface;
- sexual and asexual reproduction.
Parasitic Unicellular
The simplest have mastered many habitats: soil, fresh and salt ponds, and swamps. Among them there is also a group of parasitic unicellular. They develop in various organs of animals and humans, while causing serious diseases.
One of them is malarial plasmodium. The dimensions of this parasite are microscopic. Depending on the type, the plasmodium cell may take the form of a ball, an elongated cord or ring. In total, there are about 180 of them in nature. But 10 species are parasitic in the human body, of which 5 are the most dangerous.
Medical history
The malarial plasmodium, whose life cycle we are considering, causes a serious infectious disease. Translated from Italian, its name means "bad air." For a long time it was called swamp fever.
Scientists suggest that the first cases of malaria were known 50 thousand years ago in Central and West Africa. Evolutionary research has led to the conclusion that the ancestor of the modern species was first free living. Over time, he adapted to living in the intestines of invertebrates, and then the first bloodsucking.
The cause of this fatal disease has long been unknown. Only at the end of the 19th century, the French doctor Charles Laveran, who was practicing in Algeria, discovered unknown cells in the patient's red blood cells. For this discovery, he was awarded the Nobel Prize.
Malaria plasmodium cycle: scheme
Like all representatives of the Sporoviki type, this parasite has a complex life cycle. It proceeds with a change of owners: intermediate and final. In the body of the first, the parasite multiplies asexually. The cycle of development of malarial plasmodium in the body of the final host continues. There is sexual reproduction of the parasitic animal.
During its development, malarial plasmodium passes through the following stages:
- Human liver cells.
- Red blood cells.
- Blood of a mosquito.
Further, through a bite, the parasite again enters the human body and the cycle repeats.
Asexual reproduction
The intermediate host of the parasite is a person. It is in his body that plasmodium multiplies asexually. This happens by dividing the cell in two.
How does this organism get into human blood? This occurs when a mosquito bites an infected malarial plasmodium. The stages of its development that occur in the body of the intermediate host can be divided into several stages.
First, plasmodium with a blood stream enters the cells of the human liver. Here it propagates by schizogony. During this process, the nucleus is divided many times, around each of the formed parts the cytoplasm is secluded. After this, the newly formed cells divide again.
After several such divisions, the parasite cells enter the bloodstream. Their development occurs in red blood cells. Plasmodium continues to repeatedly divide, while destroying blood cells. Their defeat occurs quickly enough - a maximum of 72 hours.
With the destruction of red blood cells, toxic plasmodium vital products enter the bloodstream. It is they that cause a person's fever attacks. As a result of several successive divisions from the cells of the parasite, precursors of germ cells are formed, which are called gametocytes.
Ultimate host
The cycle of development of malarial plasmodium continues in the mosquito. He becomes infected with a parasite when bitten by people with malaria. The mosquito is the final host, because it contains dangerous cells that reproduce sexually.
With a bite, gametocytes from red blood cells penetrate the blood of a mosquito. Here they turn into full-fledged germ cells. The process of fertilization occurs in the intestines of the insect. As a result, numerous motile cells of the parasite are formed.
Further, the life cycle of malarial plasmodium is repeated. Its cells accumulate in the salivary glands of the mosquito, and when bitten, they again fall into the human bloodstream.
Dangerous symptoms
The genus Malaria mosquitoes has more than 400 species. Do not think that their representatives live only in African countries. They are ubiquitous, except in the northern regions. Characteristic features of adult insects are an elongated body, long legs and proboscis, short head. Their wings along the veins are covered with scales.
The bite of such a mosquito is the most common way of contracting malaria. But the cause may be non-sterile medical instruments. The first symptom of a disease is the appearance of a fever. With the destruction of red blood cells, an increase in the size of the spleen, compaction of the liver, and the development of anemia are observed.
So, the life cycle of a malarial plasmodium is characterized by a change of owners: intermediate and final. The first is man. In the cells of his blood, asexual propagation of plasmodium occurs through schizogony. The ultimate host of the parasite is a mosquito. In his body, parasite cells reproduce sexually. Malaria develops only if it is possible to repeat the stages of the life cycle. Otherwise, a dangerous disease does not develop.