Despite the development of medicine, one of the most common diseases in modern times remains malaria. Although there are now drugs for her successful treatment, but every year it takes the lives of almost two million people. Malaria belongs to protozoal diseases and is caused by a small parasite - plasmodium malaria. It has a complex development cycle, and it can exist only in the carrier organism. Therefore, you can get malaria with a mosquito bite. It is the main host of malarial plasmodium. And man is his intermediate master.
What is malarial plasmodium?
The causative agent of the disease is a unicellular organism. It belongs to the kingdom of the protozoan, a group of plasmodia. Only four species of the vast number of these microorganisms parasitize in the human body and cause malaria. This parasite is also referred to as a suborder of blood sporozoans, since it multiplies in the blood cells, feeds on hemoglobin and is transmitted with blood.
The peculiarity of protozoa is that they
consist of one cell, but function as an independent organism. What is malarial plasmodium? Its structure is similar to that of an ordinary cell, but only a little more complicated, since it goes through stages throughout its life. This organism not only divides, but also changes shape, grows and multiplies sexually and asexually.
Types and structure of parasites
Only four types of malarial plasmodia cause disease in humans. The structure and life cycle are the same, the differences are only in the ways the disease is manifested. In accordance with this they are named:
- the causative agent of tropical malaria;
- the causative agent of three-day malaria;
- causative agent of four-day malaria;
- the causative agent of oval malaria.
What is malarial plasmodium? The structure of this microorganism is different at different stages of development. Plasmodium enters the human body in the form of a sporozoid - a thin worm-shaped unicellular organism with a length of only 5-8 microns. After incorporation into red blood cells, it takes the form of an amoeba, grows and destroys blood cells. A parasite can also exist in the form of gametocyte germ cells, and in the mosquito body they merge into a sporocyst.
Life cycle of malarial plasmodium
It is a complex process. During evolution, the parasite adapted to live only in the body of other organisms, choosing two hosts for this: a mosquito and a person. Therefore, malaria infection occurs mainly through an insect bite or directly through the blood. It is believed that the ultimate host of malarial plasmodium is humans. After all, it is he who has the symptoms of the disease, and the mosquito does not even notice that it is a carrier. But in fact, it is in the body of the insect that sexual reproduction of the parasite occurs. Therefore, scientists have proved that man is an intermediate host of malarial plasmodium. What development cycle does the parasite go through?
1. When infected blood is sucked, immature germ cells of plasmodium enter the mosquito. It is there that they are fertilized and, attached to the mosquito’s stomach, begin to divide. The total number of sporozoids of the parasite can reach hundreds of thousands, a greater number of them are in the salivary glands of the mosquito. That is why the insect is the main host of malarial plasmodium.
2. When a mosquito bites, sporozoids enter the human blood. There the parasite goes through two phases of development. It divides in the liver, forming merozoites, and then penetrates the red blood cells, where it undergoes asexual reproduction.
The main host of malarial plasmodium
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 of all this process is at 25-28 degrees. Plasmodium germ cells that enter the mosquito body can be fertilized only there. After 10-15 minutes, a zygote is formed, which turns into a sporocyst and attaches to the outer wall of the insect’s stomach. There she begins to share. In one sporocyst, several thousand sporozoids are formed. And there can be a huge number of such fertilized cells in the mosquito.
Therefore, the number of sporozoids can reach hundreds of thousands. They spread throughout the mosquito, accumulating in its salivary glands. This is how the sporozoids of malarial plasmodium penetrate human blood.
The life of a parasite in the human body
When a mosquito bites, which is a carrier of a microorganism, malarial plasmodium enters the bloodstream of a person. The parasite in the body passes through two phases of development: tissue and erythrocyte. It is in the second stage that plasmodium 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 enter the bloodstream, invading red blood cells. This stage does not cause any symptoms and lasts from 5 to 16 days. In some cases, for example, when plasmodium is infected with common malaria, some of the sporozoids remain in the liver in hibernation, causing a relapse of the disease after six months.
2. When plasmodium leaves the liver in the blood, it penetrates into red blood cells, and the cyclic process of erythrocytic schizogony begins. Eating hemoglobin, merozoites develop and divide, forming new cells: asexual schizonts and sex - gametocytes. Destroying the red blood cell, they exit into the blood plasma. At this point, a person begins an attack of fever. When gametocytes form in the blood of a person, it becomes a source of infection, and with a mosquito bite, plasmodium enters the body of the insect and begins sexual reproduction there.
The development of a parasite in human blood
Why is malarial plasmodium so dangerous for humans? Its reproduction in human blood leads to the destruction of red blood cells. In these blood cells, the parasite undergoes a number of changes: merozoites go into the trophozoid stage, which feeds on hemoglobin and grows rapidly, then schizonts form. They reproduce asexually and destroy the red blood cell. In this case, a foreign protein, potassium salts, the remains of destroyed blood cells and metabolic products of the parasite enter the bloodstream.
In addition to fever attacks, this process causes disruption of the liver and spleen, leading to the growth of connective tissue in them. The breakdown of red blood cells also causes anemia. The brain is often affected, which occurs due to an increase in capillary permeability.
Features of Malaria
This disease, called "swamp fever", has been known since antiquity. It was distributed in all tropical countries. It was only in the 17th century that the disease was successfully treated with the help of the cinchona bark. And at the end of the 19th century, the causative agent of malaria was discovered. And only in the middle of the 20th century the life cycle of malarial plasmodium was studied in detail, effective drugs for the treatment of the disease were created. Despite this, more than 300 million people still fall ill with malaria every year in hot countries. About two million cases are fatal. This disease is characterized by four stages:
- The incubation period in which there is weakness, headache.
- The second stage, febrile. It begins with a strong chill. At this time, the pulse quickens, the pressure rises, and the patient cannot warm up. After 1-3 hours, the temperature rises sharply - up to 41 degrees, delusions, convulsions and a headache are observed. After this, the temperature drops, which is accompanied by severe sweating.
- After 10-12 attacks, the infection decays and a secondary latent period is observed.
- If the treatment was incorrect, then a relapse of the disease occurs in a few months. It can also occur in the event 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 sleeping state.
What is the danger of the disease
In addition to recurring periods of fever, malaria causes a malfunction of all human systems and organs. Myocardial dystrophy, neuritis, migraine, nephritis, thrombocytopenia, and anemia may develop. The liver and kidneys are severely affected. In some cases, the disease proceeds in a chronic form and is difficult to treat. Children are especially susceptible to infection - mortality among them is quite high. Until now, the disease is very common in Africa, Australia, South America, on the coast of the Red and Mediterranean Seas, in Southeast Asia and in 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 malarial plasmodium is a mosquito. And in tropical countries, especially with a humid climate, there are a lot of these insects. Therefore, the most important thing in the prevention of the disease is to protect yourself from insect bites. You can use mosquito nets or repellents for this. Many drugs are now used to treat the disease in case of infection: Chlorozin, Meflohin, Primakhin, Akrikhin and the quinine, known since the 19th century. They not only quickly stop the symptoms of the onset of an attack, but also completely destroy the parasite. People living in a tropical area and having suffered the disease acquire immunity to this type of pathogen, but may be carriers of infection, and those who intend to travel to such countries are advised to constantly take antimalarial drugs.