Amoebiasis: what is it, symptoms, treatment, prognosis, complications

What is amebiasis?

Amebiasis, or amoebic dysentery - intestinal infection caused by a single-celled protozoan parasite (amoeba), which is characterized by deep ulcerative damage to the wall of the large intestine, and sometimes the liver and other organs. The disease is ubiquitous, but endemic in areas with hot climates.

Amoebiasis is mostly common in areas with low hygiene standards. Most cases of infection are recorded in parts of Africa, the Indian subcontinent, as well as in parts of Central and South America.

Globally, about 50 million people develop amoebiasis every year, and up to 100,000 of them die.

Cause and risk factors

The cause of amoebiasis is the ingestion of one of the varieties of amoebas into the human digestive tract, Entamoeba histolytica. In this case, the greatest danger is the histolytic amoeba.

It comes in 2 forms:

• active vegetative form, which can exist in two types: large vegetative form (BWF) and small vegetative form (IMF). BVF resides in the thickness of the intestinal wall and consumes erythrocytes; when BVF goes into the intestinal lumen, then it undergoes degenerative changes and turns into IMF, which is found more often in the feces of a sick child.
• inactive form - cysts: the amoeba transforms into this form under any unfavorable conditions; with the help of cysts, amebiasis spreads.

BVF, or tissue form, is available only in the patient. IMF and cysts are present in carriers of amoebas. The source of amoebic infection is a person with amoebiasis and a practically healthy carrier of amoebas. The disease is spread by food and water.

More important is the waterway, in the absence of proper sanitary supervision of the water supply. The cause of infection can be a salad of vegetables washed with water from a pond. Contamination also occurs when contaminated bathing water is swallowed.

Flies carry the infection.

If the vegetative form of amoebas gets into the food, then the disease does not develop, since amoebae die under the influence of hydrochloric acid contained in gastric juice. Amoebiasis develops when the product is infected with amoeba cysts.

Amoeba cysts in the intestine are converted to the luminal form (IMF). The disease will develop when the luminal form turns into tissue. It multiplies in the thickness of the intestinal wall, forms small abscesses (abscesses), which open up and ulcers develop as a result. When these deep ulcers heal, scars form, sometimes causing the intestinal lumen to narrow.

With blood, amoebas penetrate liver or other organs (brain, lungs) and cause the formation of the same abscesses in these organs.

Signs and symptoms

The incubation period of amoebiasis is quite long: it lasts from 7 days to 3 months. The onset of the disease is acute. The patient may be disturbed by a headache and severe pain in the left abdomen. The temperature is normal. An increase in temperature can be noted with a mixed infection (amebiasis and bacterial infection).

One of first characteristic signs amoebiasis is the appearance of bloody diarrhea and excruciating painful urge to defecate. The stool is loose or mushy, very frequent, with a lot of mucus and blood. The mucus has a glassy or jelly-like appearance. Blood mixes with mucus and as a result, this stool resembles "raspberry jelly".

The patient's appetite is significantly reduced, people quickly lose weight, have an emaciated appearance. The skin becomes dry, wrinkled, the abdomen is sunken. With deep damage to the intestinal wall, intestinal bleeding can occur, sometimes severe, even leading to the patient's death.

The acute period of amebiasis can last up to 1.5 months and then turn into a chronic form. Amoebiasis is characterized by a tendency to chronicity of the process. In this case, the alternation of periods of exacerbation with periods of well-being continues for a number of years. Diarrhea alternating with constipation, a selection appears periodically blood with feces. The body of children and the elderly is depleted much more strongly than adults, severe malnutrition is noted, and anemia.

Complications

In addition to intestinal bleeding, anemia and malnutrition, amebiasis can lead to the following complications:

• appendicitis: develops with the penetration of parasites into the appendicular process;
• peritonitis: can develop when the amoeba enters the abdominal cavity through the intestinal wall; inflammation of the peritoneum occurs;
• lung abscess, liver and / or other internal organs: can develop with any severity of amoebiasis and at any period of the disease; abscesses can be single or multiple;
• paraproctitis: inflammation of the tissue around the rectum;
• narrowing of the intestinal lumen due to scarring of ulcers;
• amoeba: a tumor-like formation that sometimes forms in the lumen of the intestine and leads to intestinal obstruction.

Diagnostics

To diagnose amoebiasis, the doctor needs to take samples of the patient's feces. The best approach is to analyze feces for a protein produced by amoebae (antigenic test) or to identify the genetic material of amoebae by means of a polymerase chain reaction (PCR). The PCR method reproduces multiple copies of the amoeba's genetic material and thus makes it easier to detect amoebae. These tests are more effective than examining stool samples under a microscope, the results of which are often questionable. In addition, microscopic examination may require three to six stool samples to detect amoebas, but even if they are detected Entamoeba histolytica can not always be distinguished from other species of amoeba, such as Entamoeba disparthat have a similar appearance, but a different genetic structure and do not cause disease.

A flexible viewing tube (endoscope) can be used to view the colon. If ulcers or other signs of infection are found, an endoscope is used to obtain a sample of fluid or tissue from the infected area.

When amoebae move outside the intestines (for example, into the liver), they may no longer be found in feces. Ultrasound, CT, or MRI scans may be ordered to confirm a liver abscess, but these types of scans do not indicate the cause. A blood test is done to check for antibodies to amoeba. (Antibodies are proteins made by the immune system to protect the body from attacks, including parasites.) Or, if the doctor suspects a liver abscess caused by amoebae, the patient may be prescribed drugs that destroy these microorganisms (amoebicides). If the patient is getting better, the most likely diagnosis is amebiasis.

Standard treatments

People with suspected amebiasis are hospitalized in the infectious diseases department, where an examination is carried out to clarify the diagnosis.

The main treatment is the appointment of antiparasitic agents. For this purpose, they are used: Emetina hydrochloride, Delagil, Chloroquine, Metronidazole, Tinidazole, Trichopolum, Flagil. Antibiotics (Monomycin, Tetracycline) can also be used. The drugs are prescribed in an age-specific dosage, in two 7-day courses with an interval of 7 days.

With the formation of amoebic abscesses, treatment is carried out for a longer time until the stage of resorption of the abscess. In the case of a large liver abscess, surgical treatment is used.

Symptomatic therapy is also carried out: intravenous administration of solutions for water-electrolyte disturbances; iron preparations and blood substitutes for anemia. It is equally important to provide the patient with a nutritious diet containing a sufficient amount of protein and vitamins. It is recommended to limit the amount of carbohydrates.

Recovered patients are under the supervision of an infectious disease specialist for 1 year with the passage of a quarterly follow-up examination. For the treatment of carriers of amoeba, Metronidazole, Furamid, Tetracycline, Delagil are used.

Forecast

If left untreated, amoebic infections have a very high morbidity and mortality. In fact, mortality is second only to malaria. Amoebic infections tend to be most severe in the following populations:

• pregnant women;
• postpartum women;
• newborns;
• malnourished people;
• persons receiving corticosteroids;
• persons with malignant neoplasms.

When the disease is treated, the prognosis is good, but recurrent infections are common in some parts of the world. Post-treatment mortality is less than 1%. However, amoebic liver abscesses can be complicated by intraperitoneal rupture in 5–10% of cases, which can increase mortality. Amebic pericarditis and pulmonary amebiasis have high mortality rates in excess of 20%.

Today, with effective treatment, the mortality rate among patients with uncomplicated disease is less than 1%. However, rupture of an infected amoebic liver abscess leads to high mortality.

Prophylaxis

A reliable method of preventing amoeba infection is to observe the rules of hygiene and sanitation.

Drinking water can be secured by boiling, using filters. Store water in closed containers. Fight against flies, protection of food products from them is important for the prevention of disease. When swimming in bodies of water, do not allow water to be swallowed. In endemic regions, boiled water should also be used when brushing teeth, washing dishes, and making ice cubes.