Generality
The term amoebiasis identifies a generic presence of the Entamoeba histolytica parasite within the organism; this presence can be substantially asymptomatic and harmless, and in this case we speak of commensal amoebic infection, or produce tissue lesions accompanied by severe symptoms, first of all dysentery. In the latter case we speak of amoebic disease.
Epidemiology and Contagion
It is estimated that worldwide about 10% of the population lives in its own intestine Entamoeba species; in most cases this infection is supported by the species E. dispar (harmless), while only one case out of ten is associated with the potentially pathogenic species Entamoeba histolytica. The latter, in turn, generates amoebic disease in about 10% of cases each year.
The spread of the disease is favored by poor hygienic conditions and hot humid climates; thus, if in the United States of America about 4% of the population hosts a parasite of the Entamoeba genus in its intestine, in some developing countries this percentage may exceed 30%. Within the same population, homosexual males (due to the greater risk of infection) and immunocompromised individuals (due to the decrease in immune defenses, eg HIV-positive, malnourished or patients treated with immunosuppressive or antineoplastic ). In the latter case, the risk of commensal infection evolving into amoebic pathology is also greater; similar speech in the extreme ages of life, during pregnancy and lactation.
As anticipated, the transmission of amoebiasis can take place by sexual means, following oral-anal and oro-genital contacts (it is therefore part of sexually transmitted diseases). However, the most common route of transmission is the fecal-oral route, therefore linked to the ingestion of water or food (especially fruit and vegetables) contaminated by fecal material containing amoebic cysts (the quiescence stage of the microorganism). These cysts can survive for a long time in the external environment: at temperatures between 12 and 15 ° C, for example, they retain their infectious capacity for at least 12 days inside the feces, and for several weeks inside the waters. Once ingested, the cysts overcome the acidic barrier of the stomach without any problems and catch themselves at the level of the colon where, favored by dehydration of the feces, they give rise to 4 trophozoites each. The latter, which represent the "active" and mobile form of the parasite, feed on bacteria and tissues; once released outside through the faeces, the trophozoites survive only for a few minutes and, even if ingested, would be killed by gastric juices.
Considering that, in most cases, amoebic infection is asymptomatic, amoebiasis can be transmitted not only by sick subjects, but also by so-called "healthy guests" who - without presenting any sign of the disease - chronically expel cysts with I also did it for a few years.
Symptoms
To learn more: Symptoms of Amoebiasis Syndrome
After an incubation period, ranging from a few days to a few months or years (usually 2-4 weeks), amoebiasis can present with clinical pictures of variable severity from chronic moderate diarrhea, alternating with periods of constipation, to severe dysentery acute fulminant. This symptom is due to the direct attack of amoebic trophozoites on the colon cells, which - when important - can cause blood diarrhea and the presence of mucus in the stool. Added to this is a set of secondary symptoms of varying intensity depending on the severity of the infection: flatulence, more or less high fever, anemia, mucorrhea, weight loss, weakness, rectal tenesmus, nausea and cramped abdominal pains.
For the alternation of periods of constipation with others of constipation, non dissenteric amoebiasis can be confused with irritable bowel syndrome or diverticulitis. Amoebic dysentery can instead be confused with shighellosis, salmonellosis, schistosomiasis or ulcerative colitis
Thanks to the synthesis of specific proteases, the amoebae are potentially able to attack the extracellular matrix and open a gap in the intestinal wall, entering the portal circle through which they reach the liver, where they can cause necrotic liver abscesses. The patient suffering from amoebiasis can therefore complain of pain on the liver (with hepatomegaly) and ascending colon.
Dagnosi
The diagnostic confirmation is obtained through the detection of amoebic cysts in fecal samples. Alternatively, the diagnosis can be made by proctoscopy: an invasive endoscopic examination of the rectum and the last part of the colon, during which the intestinal walls are observed and small samples are removed (generally corresponding to infectious lesions) for the laboratory analysis. Even serological tests, by searching for specific antibodies in the blood, can be useful in the diagnosis of amoebiasis.
Care and drugs
The treatment of amebiasis depends on the severity of the infection.
Generally, in symptomatic patients the preferred therapy is represented by the antibiotic metronidazole, taken orally (5-10 days of therapy with 750 mg per day for adults, and 35-50 mg / kg / day in 3 divided doses for children).
Antidiarrheal drugs are generally not recommended; rather, supportive hydrosaline hydration therapy to compensate for diarrheal water and electrolyte losses is important.
Asymptomatic patients who eliminate cysts through the faeces is usually prescribed a course of oral diloxanide furoate (500 mg / day for 10 days in adults or 20 mg / kg / day in 3 divided doses in children).
Continue: Drugs and Treatment of Amebiasis »
Prevention of infection
Particular attention must be paid to respecting the essential hygiene rules to avoid faecal-oral transmission diseases; when staying in tropical or sub-tropical developing countries:
- drink only safe water, that is water that has been boiled, or disinfected with chlorine or iodine, or bottled mineral water, whose bottle is opened in your presence
- avoid ice, unless you are absolutely sure that it was produced with safe water
- consume only food that has been carefully cooked and is still hot at the time it is served
- protect food from annoying insects by means of nets, or in special containers
- refrigerate foods that are not consumed immediately after preparation
- avoid raw seafood and fish
- avoid consuming vegetables and raw fruit, unless they have been washed, peeled, prepared by yourself: remembering the saying: cook it, peel it, or leave it alone
- boil the unpasteurized milk before consuming it
- avoid ice cream and cream desserts that could have been packaged with unpasteurized milk or have been recontaminated
- make sure that the food purchased from street vendors has been completely and carefully cooked in your presence and does not contain raw parts
- always wash your hands thoroughly after going to the toilet and before eating.
