Dysenteric amoeba is the simplest parasite, which, falling into the inside of a person, causes severe pathologies: amoebic dysentery and amoebic colitis. Like other amoebas, they have adapted to a parasitic existence within a person in the colon, but under certain conditions can cause a serious disease - amoebiasis. Described for the first time in 1875 by the scientist Lesch, are widely distributed around the globe, but the inhabitants of tropical and subtropical countries are most susceptible to the disease. In other climatic zones, people are more often carriers of dysentery amoeba, and outbreaks of amoebiasis are rare.
Structure of the dysentery amoeba
The structure of the dysentery amoeba is the following: it is an individual that constantly changes its contours, the value of 20-30 micrometers, has a spherical core inside the endoplasm - inner contents, is covered by ectoplasm - the outer layer of the cell cytoplasm, there is no skeleton, very mobile, moves with the help of peculiar processes called pseudopodia or pseudopods. Its movement resembles a flow from one outline to another. There is a luminal, tissue, large vegetative form of amoeba and in the form of cysts. The size of the luminal is about 20 microns, it is located in the lumen of the upper part of the large intestine, feeds on its bacteria and does not do any harm to the wearer.
Life cycle of the dysentery amoeba
The life cycle of dysenteric amoeba begins when ingested in the gastrointestinal tract. Ways of infection with dysenteric amoeba fecal-oral, household. Together with the feces, cysts are released into the environment, over 300 million are released per day. They show great resistance to temperature changes and other adverse effects. So, cysts are able to remain for a month at a temperature of 20 ° C, a week in a moist and darkened environment, up to a week in chilled food, several months at minus values. They enter the person with dirty hands, unwashed products, contaminated water, by tactile contact with the hands of a sick person. Their carriers are flies and cockroaches. Factors associated with the development of pathology are pregnancy, protein deficiency, dysbacteriosis, worms - all that reduces immunity.
Cyst of dysentery amoeba
Cysts of dysenteric amoeba appear from the vegetative after the remission of the acute phase of the disease. Some of them turn into a luminary, others, appearing in a medium of condensed feces, become smaller, enveloped and encysted. They have 4 cores and are arranged in the same way as the nuclei of the vegetative form. Immature cysts can have from one to three cores. This is the most resilient form of dysenteric amoeba that can survive in an unfavorable environment and, once inside a person, resume the life cycle.
Invasive stage of dysentery amoeba
The invasive stage of the dysentery amoeba is characterized by an incubation period that lasts up to two weeks. At this time, the cysts move along the intestine. On the way of their progress, they are introduced into its mucous membrane. In this case, the transverse and descending parts of the large intestine are most vulnerable to injury. At this stage, moving, the cysts turn into a vegetative form that contains destructive enzymes for the intestinal walls - pepsin and trypsin. This helps the parasite to penetrate into its layers, down to the muscular ones, which becomes tangible to the person.
Tissue form of dysentery amoebae
The tissue form of the dysenteric amoeba is formed by the introduction of the luminal in the intestinal wall. Until now, scientists have not figured out the reason why this happens. But at this stage, amoeba damages the mucosa of the colon. It is this form of its existence that is found in patients with amoebiasis. Breeding, it provokes the formation of ulcers on the walls of the intestines, which lead to the accumulation of pus, blood, mucus. Conditions are created for the transformation of luminal and tissue forms into a larger vegetative form. They increase to 30 μm and are able to absorb red blood cells. Going outside, the vegetative form dies.
Since the damage of the walls, clinical symptoms of dysentery amoeba are manifest . The signs of acute amoebiasis grow gradually with obvious dynamics. In the beginning, the chair gets more frequent 4-6 times a day, feces of liquid consistency with mucus having a sharp and unpleasant smell. Gradually, trips to the toilet all increase and can reach 20 times, there are false desires for defecation, in the vitreous mucus are found blood clots. The body temperature rises to 38 ° C, which lasts for several days, the stomach is swollen and painful. Treatment of the disease can last up to a month and a half, if not, then remission occurs and the pathology becomes chronic. Her symptoms are expressed in a white scurf in the tongue, bad breath, poor appetite, weight loss, signs of vitamin deficiency (hair loss, brittle nails, pale skin), tenderness of the abdomen. Over time, there may be violations of the heart and liver.
Diagnosis is carried out by the method from simple to more complex and is initially based on the patient's story about the symptomatology: the frequency and nature of the stool, the pain, the dynamics of the development of the disease, and also the temperature is measured. Then the material for laboratory research is taken. If there is no possibility of getting stool, endoscopy takes biopsy samples, and also examines the walls of the intestine for damage, the presence of ulcers. As additional methods resort to ultrasound of the kidneys, abdominal organs to assess their condition.
Laboratory diagnostics consists in examining under a microscope feces, biopsy specimens taken from damaged foci. In case of complications, scrapings from the nasopharynx are taken. The presence of amoeba (trophozoites) in the investigated cyst and vegetative form confirms the diagnosis. For their better detection, strokes are stained. In biopsy specimens with amoebiasis, trophozoites with erythrocytes are found inside. Express diagnostics using the Koons method for the detection of antibodies is also used. It consists in the fact that the smear is stained with luminescent serum, the bacteria on this background have a green rim around the perimeter. Another similar method - an enzyme-linked immunoassay based on the antigen-antibody reaction - is also used in laboratory diagnostics.
When a case of dysentery is detected, it is necessary to determine the source of the carrier in order to prevent the spread of mass infection. To do this, the dysenteric amoeba is reported to the Sanitary Service, which disinfects the food outlets, if the infection has occurred there, or other places. Also examine persons who are in contact with the patient or working in public catering for the carriage of cysts.
The task of differential diagnosis is to distinguish between dysenteric amoeba and intestinal amoeba . Their difference in structure: the dysentery shell is a two-contour, refracting light, it has 4 nuclei (in the intestinal - 8), located eccentrically, it includes blood cells, which is not in the intestinal. Dysentery amoeba is more vigorous in movement.
In many ways, the symptoms are similar to malaria. Her pathogen is malarial plasmodium. The plasmodium carriers are mosquitoes, and man is an intermediate host. With the bite of an insect, unlike a dysentery amoeba, plasmodium enters the bloodstream, and then into the liver, where asexual reproduction occurs, the so-called tissue schizogony. As a result of multiple division, which occurs in the incubation period, many daughter cells appear that absorb hemoglobin and destroy liver cells. Malaria is accompanied by severe attacks of fever, chills and signs of intoxication of the body.
Several groups of drugs have been sent to treat dysentery amoeba . Some of them kill the luminal form of amoeba, are used at the stage of remission in case of chronic disease and for the prevention of the disease. Such drugs are called "direct amoebicides", they include: diiodohin, quinophone. In the acute course of dysentery, medicines directed to tissue and luminal forms are used: quinamine, emetine, ambilgar, dihydroemitin. There are universal preparations, such as furamide, trihopol. Also used are antibiotics, enzyme and microflora-restoring intestinal preparations. In a complex with medicamental treatment, a special dietary protein diet is mandatory, eliminating coarse spicy food. The food should be frequent, but in small portions, at first - food in the grated form. In the presence of serious complications, even surgical intervention is possible.
Prevention of the dysentery amoeba
There are no special preventive measures. The best prevention is the observance of sanitary and hygienic rules: frequent washing of hands, vegetables and fruits, boiling of drinking water, preventing from falling on the beds of faeces from toilets, fighting cockroaches. When detecting outbreaks, it is important to identify carriers of dysentery amoeba.
The prognosis of amebiasis with a timely begun treatment is favorable. In the event that the patient's condition is complicated by breakthrough abscesses, intestinal bleeding, narrowing of intestinal tracts or penetration of dysenteric amoebae into other organs: liver, brain, lungs, then a fatal outcome is possible.
It is known that 50 million. People on Earth are infected with dysentery amoeba. And if you consider that in many countries in Africa there is no accounting for morbidity, and the environment for the spread of amoebiasis is the most suitable, it is not difficult to imagine the extent of the spread. Statistics say that about 100 thousand people die each year from this disease. Human. The interesting fact is that scientists still can not understand why in some organisms the individuals peacefully coexist with the host, in others they aggressively penetrate into the tissues of his entrails, eating live cells and causing significant harm to the body.
Amoeba was discovered in 1757 by a German scientist entomologist (a science that studies insects) by Rösel von Rosenhof, thanks to the water spilled on a microscope. After 200 years, it turned out that the unicellular organism that he observed was completely different. Its name was given to amoeba in 1822 and it means "variability" because of its ability to constantly change shape. Moving, the amoeba stretches out in length, in the front part of it pseudopodia are shown. For a long time scientists could not unravel this mechanism, and having unraveled, were surprised by such a complex device of movement, which could arise only as a result of a long evolution. Genetics also found a gene too long for a unicellular organism. Watching this form of life for several centuries, scientists are only convinced that not everything is so simple with this individual. For sure, we are waiting for more new discoveries related to the amoeba.
Last update: 25.06.2018
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Medical expert editor
Portnov Alexey Alexandrovich
Education: Kiev National Medical University. A.A. Bogomolets, Specialty - "General Medicine"
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