The main host of the malarial plasmodium. Life cycle, structure, multiplication of a parasite

Despite the development of medicine, malaria remains one of the most common diseases in modern times. Although there are now drugs for its successful treatment, but annually it takes the lives of almost two million people. Malaria refers to protozoal diseases and is caused by a small parasite - a malarial plasmodium. He has a complex development cycle, and he can exist only in the body of the carrier. Therefore, you can catch malaria if you bite a mosquito. This is the main owner of the malarial plasmodium. And man is his intermediate master.

What is a malarious plasmodium

The causative agent is a unicellular organism. It refers to the sub-archeology of the protozoan, the plasmodial order. Only four species from a huge number of these microorganisms parasitize the human body and cause malaria. This parasite is also referred to as the suborder of blood sporoviks, as it multiplies in blood cells, feeds on hemoglobin and is transmitted with blood. A feature of the simplest is that they consist of a single cell, but function as an independent organism. What is the malarial plasmodium? Its structure is similar to that of an ordinary cell, but only somewhat more complex, since it passes through its life as far as the stages. This organism not only shares, but also changes shape, grows and reproduces sexually and asexually.

Types and structure of parasites

Only four types of malarial plasmodia cause disease in humans. The structure and life cycle they have the same, the differences only in the ways of manifestation of the disease. In accordance with this they are named:

- causative agent of tropical malaria;

- causative agent of a three-day malaria;

- causative agent of four-day malaria;

- causative agent of oval malaria.

What is the malarial plasmodium? The structure of this microorganism is different at different stages of development. It enters the human body plasmodia in the form of a sporozoid - a thin vermiform unicellular organism with a length of only 5-8 μm. After introduction into erythrocytes, it takes the form of an amoeba, grows and destroys blood cells. The parasite can also exist as gametocyte gametes, and in the mosquito they merge into a sporocyst.

Life cycle of malarial plasmodia

It is a complex process. During the evolution of the parasite has adapted to live only in the body of other organisms, choosing for this two hosts: a mosquito and a human. Therefore, malaria infection occurs mainly through an insect bite or directly through the blood. It is believed that the final owner of a malarial plasmodium is a person. After all, he has symptoms of the disease, and the mosquito does not even notice what is the carrier. But in fact, it is in the insect organism that the parasite reproduces sexually. Therefore, scientists have proved that man is an intermediate host of a malarial plasmodium. What is the development cycle of the parasite?

1. When sucking infected blood into the body of a mosquito, immature sex plasmodium cells enter. It is there that they fertilize and, attaching themselves to the stomach of a mosquito, begin to share. The total number of sporozoids of the parasite can reach hundreds of thousands, more of them are in the salivary glands of the mosquito. That is why an insect is the main owner of a malarial plasmodium.

2. When a mosquito bites, sporozoids enter the human blood. There the parasite passes through two phases of development. It is divided in the liver, forming merozoites, and then penetrates into the red blood cells, where it undergoes asexual reproduction.

Main host of malarial plasmodia

The carrier of the disease is a female mosquito of one species - living in a hot climate. This is due to the fact that the development of malarial plasmodium is possible only at temperatures above 16 degrees. And most actively this process is at 25-28 degrees. Sex plaemodia cells found in the mosquito can only be fertilized there. Already in 10-15 minutes a zygote is formed, which turns into a sporocyst and adheres to the outer wall of the insect stomach. There she begins to share. In one sporocyst, several thousand sporozoids are formed. And such a fertilized cells in the body of a mosquito can be a huge amount. Therefore, the number of sporozoids can reach hundreds of thousands. They spread through the mosquito's body, accumulating in its salivary glands. This is how the sporozoids of the malarial plasmodium penetrate the human blood.

Life of a parasite in the human body

When a mosquito bites, which is the carrier of a microorganism, malaria plasmodium enters the human blood. The parasite in the body passes through two phases of development: tissue and erythrocyte. It is in the second stage of plasmodium and causes the symptoms of malaria.

1. The first phase is called tissue schizogony. Penetrating into the liver cells, the sporozoid begins to divide, forming up to 50 thousand merozoites. They go to the blood, penetrating into the red blood cells. This stage does not cause any symptoms and lasts from 5 to 16 days. In some cases, for example, when infecting with plasmodium trednevnoy malaria, part of the sporozoids remain in the liver in hibernation, six months later causing a relapse of the disease.

2. When the plasmodium leaves the liver into the blood, it enters the erythrocytes, and the cyclic process of erythrocytic schizogony begins. Feeding on hemoglobin, the merozoites develop and divide, forming new cells: sexless schizonts and sex - gametocytes. By destroying the erythrocyte, they exit into the blood plasma. At this moment, a person has a fever attack. When gametocytes form in the blood of a person, it becomes a source of infection, and when a mosquito is bitten, the plasmodium penetrates into the insect's body and begins sexual reproduction there.

Development of the parasite in human blood

Why is a malarious plasmodium so dangerous for a person? Reproduction of it in human blood leads to the destruction of red blood cells. In these blood cells, the parasite undergoes a number of changes: the merozoites pass to the stage of the trophozoid, which is fed by hemoglobin and rapidly grows, then schizonts are formed. They reproduce asexually and destroy the red blood cell. At the same time, foreign proteins, potassium salts, remains of destroyed blood cells and metabolic products of the parasite enter the blood. In addition to fever attacks, this process causes disruption of the liver and spleen, leading to the proliferation of connective tissue in them. Disintegration of red blood cells also causes anemia. The brain is often affected, which is due to an increase in the permeability of the capillaries.

Features of malaria

This disease, called "marsh fever", is known since ancient times. It was widespread in all tropical countries. Only in the 17th century the disease was successfully treated with the help of the cinchona bark. And at the end of the 19th century, a malignant agent was discovered. And only in the middle of the 20th century the life cycle of malarial plasmodium was studied in detail, effective medications were developed to treat the disease. Despite this, more than 300 million people are ill with malaria every year in hot countries. About two million cases end in death. This disease is characterized by four stages:

- Incubation period, in which there is weakness, headache.

- The second stage, feverish. It begins with a strong chill. At this time, the pulse becomes more frequent, the pressure rises, and the patient can not warm up. After 1-3 hours, the temperature rises to 41 degrees, nausea, convulsions and headache occur. After that, the temperature drops, which is accompanied by a strong perspiration.

- After 10-12 attacks, the infection fades and a secondary latent period is observed.

- If the treatment was wrong, then a relapse of the disease occurs in a few months. It can also arise in the case of infection with one of the plasmodium species that causes tropical malaria. Part of the sporozoids of this parasite remain in the human liver in a dormant state.

What is the danger of the disease?

In addition to recurrent periods of fever, malaria causes disruption of all systems and human organs. Dystrophy of the myocardium, neuritis, migraine, nephritis, thrombocytopenia and anemia can develop. Liver and kidneys are severely affected. In some cases, the disease occurs in a chronic form and is difficult to treat. Children are especially vulnerable to infection - the mortality among them is quite high. Until now, the disease is very common in Africa, Australia, South America, the coast of the Red and Mediterranean seas, Southeast Asia and India.

Treatment and prevention of malaria

Even in modern society it is not possible to cope with this disease. After all, the main owner of a malarial plasmodium is a mosquito. And in tropical countries, especially with a humid climate, these insects are very numerous. Therefore, the most important thing in disease prevention is to protect yourself from insect bites. To do this, you can use mosquito nets or repellents. To treat the disease in the event of infection, many drugs are currently used: Chlorozine, Mefloquine, Primachin, Akrihin and Quinine, which has been known since the 19th century, not only quickly relieve the symptoms of a beginning attack, but also completely destroy the parasite. People living in a tropical area and having a disease acquire immunity to this type of pathogen, but they can be carriers of infection, and those who are going to go to such countries are advised to constantly take antimalarial drugs.