Intestinal infections represent a large group of diseases that combines damage to the organs of the gastrointestinal tract and characteristic clinical manifestations in the form of nausea, vomiting, diarrhea (with mucus and blood) or constipation. The causative agents of acute intestinal infections can be bacteria, viruses, helminths and protozoa. This greatly complicates the diagnosis and often involves syndromic treatment.
Definition
Amoebiasis (amoebic dysentery) is an anthroponotic infection with a fecal-oral transmission mechanism. Its main manifestations are: chronic recurrent colitis and extraintestinal manifestations, such as liver abscesses, ulcers, and others. Most often, the term amoebiasis means amoebic dysentery, which is caused by the parasite Entamoeba histolytica.
Among other amoebiasis, amoebic encephalitis and keratitis are distinguished. According to the World Health Organization, about ten percent of the world's inhabitants are infected with this infection, and it is one of the main causes of death from parasitic diseases. Extraintestinal manifestations are very difficult to diagnose, so it is not always possible to diagnose and treat amoebiasis in a timely manner.
Epidemiology
Amoebic dysentery is common in all countries with a hot and humid climate. Symptoms of this disease can most often be found in people who neglect sanitary and hygienic standards. The pathogens are endemic to Central and South America, especially Mexico and India.
Sometimes large outbreaks of this intestinal infection are recorded in relatively prosperous countries, for example, in 1933 during the World Exhibition, which was held in Chicago. Currently, massive and sporadic cases of the disease appear in places where emigrants from endemic regions congregate. Most often, the infection manifests itself in the warm season.
The source of infection is a sick person or a carrier of protozoa. Infection occurs only through dirty hands, food and water. Also, the disease can be transmitted through unprotected homosexual contacts. It is known that the cystic form of amoeba can spread on the legs and wings of insects.
Pathogen
Why does amoebic dysentery occur? Its causative agent is one of the simplest, which can exist in three different forms:
- tissue (found only in sick people);
- luminal;
- cystic.
The last two are found in carriers of the disease. It is a cell up to 40 micrometers in size, which has a core and many vacuoles. For movement in the human body uses pseudopods. Bacteria, fungi, food particles are suitable for food. Amoebic dysentery is caused by this particular form.
A cyst is a round or oval cell measuring 30 micrometers in size. It can have several cores (from two to four), it depends on the stage of development.
Amoeba Life Cycle
A cyst enters the small intestine of a person through dirty hands, water or greenery. There, the cyst membrane is destroyed, and a mature maternal amoeba enters the lumen of the organ . This form begins to share. As a result of this process, eight new mononuclear pathogens are formed. Amoebic dysentery begins at this moment. With a combination of favorable conditions of the body and a sufficient number of mononuclear vegetative forms, the amoeba continue to multiply and move further deep into the intestine.
In the process of their life, protozoa secrete substances that poison a person and cause characteristic symptoms of intestinal infection. With feces, vegetative and cystic forms enter the external environment. There they are able to persist for quite some time. In addition, they are resistant to disinfectants.
Pathogenesis
How does such an ailment develop as amoebic dysentery? Infection begins with the use of unwashed food. So amoeba enter the blind and ascending colon, where they may not manifest themselves for a long time. But in unfavorable conditions for a person (dehydration, poor nutrition, dysbiosis), cysts drop their shell, and a luminous form of amoeba appears.
Using its own cytolytic and proteolytic enzymes, the pathogen penetrates the thickness of the tissues, causing inflammation and the formation of ulcers and necrosis of small areas. In some cases, amoeba enter the blood vessels and, with the flow of fluid, enter other organs, forming abscesses there.
In the intestinal form of the disease, inflammation spreads in a downward direction, from the cecum to the rectum. The mucous organ is swollen, against the background of hyperemia, small nodules and ulcers are visible that contain necrotic detritus and vegetative forms of amoebas. Over time, the nodules are destroyed, leaving in their place new ulcers up to two and a half centimeters in diameter. Deep defects at the bottom are covered with pus. If you examine the biopsy from the wall of the ulcer, you can find amoebas.
Chronization of the disease is accompanied by the formation of cysts, polyps and amoeba. These are tumor-like formations that consist of granulation tissue, eosinophils and fibroblasts.
Extraintestinal form
Amoebic dysentery has both dyspeptic manifestations and general somatic. When vegetative forms of amoeba penetrate the thickness of the intestinal wall, they can enter the systemic circulation. This leads to the spread of the pathogen throughout the body. According to the portal vein system, amoeba enter the liver parenchyma.
Lesions of varying severity can develop in the organ: from protein or fatty degeneration to severe hepatitis and liver abscess, located under the dome of the diaphragm. Sometimes it is also called a chocolate cyst because of the specific color of pus. If inflammation is not treated, spontaneous opening of the abscess in the abdominal cavity occurs with the development of peritonitis. Or a cyst can break through the diaphragm into the lungs, mediastinum or pericardium, causing corresponding complications. In addition to the liver, the pathogen can affect the brain, skin and other organs.
Clinic
The incubation period lasts about a week, after which amoebic dysentery appears. Symptoms begin with general weakness, pain in the iliac regions, and a rise in body temperature. In ten percent of cases, the disease takes on a fulminant course. It is characterized by profuse diarrhea, with blood and mucus, which causes severe dehydration and death. Somewhere in a third of patients there is a fever in combination with an enlarged liver. Inflammation at the onset of the disease is poorly expressed, therefore, in the general blood test, characteristic changes are not observed.
Other manifestations are accompanied by extraintestinal dysentery. A symptom that could be called pathognomonic is absent in this case. Amoebiasis practically does not manifest itself in the body until the critical mass of the pathogen accumulates.
If you do not take any action regarding the treatment of the disease, then after a while the infection becomes chronic. Gradually, anemia and general exhaustion develops. The lower the body's resistance, the faster the intestinal form passes into the extraintestinal. The risk category includes small children, the elderly, pregnant women and patients taking immunosuppressive drugs.
Diagnostics
What are the criteria for diagnosing dysentery? Diagnosis and treatment of this infection is closely related to the life cycle of protozoa. In order to find out the etiology of diarrhea, the doctor takes an analysis of feces, in which he finds tissue forms of amoeba. If there are cysts or luminal forms in the feces, this indicates carriage and cannot serve as a confirmation of the diagnosis.
Since several types of amoebas are already found in the human body as opportunistic flora, the diagnosis may be somewhat difficult. It is also possible to make a mistake in the diagnosis if Entamoeba dispar is detected. This is a non-pathogenic amoeba, which is completely harmless to humans, but morphologically very similar to dysentery.
Polymerase chain reaction and serological tests are also used to verify the diagnosis. To detect extraintestinal forms of amoebiasis, it is necessary to conduct an X-ray examination, ultrasound and computed tomography. Amoebic infection with shigellosis, salmonellosis and ulcerative colitis are differentiated.
Treatment
Treatment of amoebic dysentery begins with cytostatics, such as metronidazole or tinidazole. If the patient has no symptoms, then iodoquinod or paromomycin can be used to eliminate parasites.
The very first anti-amoebiasis medicine was emethine, which was extracted from Ipecac in South America. Now it is rarely used, as it is extremely toxic and not effective enough. This remedy is used only in case of a protracted course, with resistant forms and allergies to metronidazole.
For the treatment of extraintestinal forms, metronidazole is used in combination with yatren, doidochin, mexiform and other drugs. In some cases, resort to surgical intervention.
Complications
Amoebic dysentery in humans can be complicated by perforation of the intestinal wall. This occurs when the defect is too deep. With perforation, intestinal contents enter the abdominal cavity and infect it. The following complication develops - peritonitis. In order to save the patient's life, it is necessary to resort to surgical care: make a median laparotomy and conduct an audit of the abdomen.
Another formidable complication is intestinal bleeding. It also develops during the formation of ulcers. To stop it, you can use both conservative and operational methods. Healing ulcers can narrow the intestinal lumen due to the formation of scar tissue, thus disrupting the passage of food.
Prevention
Amoebic dysentery is an intestinal infection, therefore, to prevent it, it is necessary to decontaminate the pathogen sources in a timely manner: dubious reservoirs, central water supply tanks and others.
In addition, it is necessary to carry out measures to identify carriers and spores, as well as treat patients with acute forms in compliance with anti-epidemic measures. In no case should recovering people and carriers be allowed to work in places of public catering.
Another way to reduce the number of infected people is to promote personal hygiene and the proper handling of food before eating it. After the infection, a person should be regularly observed in the office of infectious diseases for a year. And only after the tests for three months are negative for amoebiasis, the patient will be considered completely healthy.