A disease caused by infection with the protozoan parasite entamoeba histolytica, acquired by ingestion of food or water contaminated with faeces containing infected cysts. Once inside the gut, the cysts hatch to release the adult organisms, which irritate the gut lining resulting in severe bloody diarrhoea. They also invade the lining to enter the blood stream, and circulate throughout the body forming cysts in the liver, lungs, and brain.
AmoebiasisClassifications and external resources
| ICD-10 | A06 |
|---|---|
| ICD-9 | 006 |
Amoebiasis is infection by a protozoan, typically Entamoeba histolytica. It is usually contracted by ingesting water or food contaminated by amoebic cysts.
Transmission
Amoebiasis is transmitted by fecal contamination of drinking water and foods, but also by direct contact with dirty hands or objects as well as by sexual intercourse.
Prevention
To help prevent the spread of amoebiasis around the home:
Wash hands thoroughly with soap and hot running water for at least 10 seconds after using the toilet or changing a baby's diaper.Nature of the disease
Symptoms are usually gastrointestinal including diarrhea, vomiting, abdominal pain or discomfort and fever. Symptoms take from a few days to a few weeks to develop and manifest themselves, but usually it is about two to four weeks.
Infections that sometimes last for years may be accompanied by
no symptoms (in the majority of cases), vague gastrointestinal distress, dysentery (with blood and mucus).Most infections occur in the digestive tract but other tissues may be invaded.
Onset time is highly variable and the average asymptomatic infection persists for over a year.
In asymptomatic infections the amoeba lives by eating and digesting bacteria and food particles in the gut.
Theoretically, the ingestion of one viable cyst can cause an infection.
Diagnosis of human illness
Asymptomatic human infections are usually diagnosed by finding cysts shed with the stool. Various flotation or sedimentation procedures have been developed to recover the cysts from fecal matter and stains help to visualize the isolated cysts for microscopic examination.
Microscopy is still by far the most widespread method of diagnosis around the world. histolytica cyst from the cysts of nonpathogenic intestinal protozoa such as Entamoeba coli by its appearance. histolytica cysts have a maximum of four nuclei, while the commensal Entamoeba coli has up to 8 nuclei. histolytica in most parts of the world this means that there is a lot of incorrect diagnosis of E. The WHO recommends that infections diagnosed by microscopy alone should not be treated if they are asymptomatic and there is no other reason to suspect that the infection is actually E.
Relative frequency of the disease
Nevertheless, this means that there are about 50 million E. histolytica infections and approximately seventy thousand die each year, mostly from liver abscesses or other complications. Infection is more common in warmer areas, but this is both because of poorer hygiene and because the parasite cysts survive longer in warm moist conditions.
Treatment
E. histolytica infections occur in both the intestine and (in people with symptoms) in tissue of the intestine and/or liver. Since most of the amebae remain in the intestine when tissue invasion occurs, it is important to get rid of those also or the patient will be at risk of developing another case of invasive disease. Both types of drug must be used to treat infections, with metronidazole usually being given first, followed by paromomycin or diloxanide.
For amebic dysentery:
Metronidazole 800mg three times a day for 5 days Tinidazole 2g once a day for 3 days is an alternative to metronidazole Diloxanide furoate 500mg three times a day for 10 days must always be given afterwardsFor amebic liver abscess:
Metronidazole 400mg three times a day for 10 days Tinidazole 2g once a day for 6 days is an alternative to metronidazole Diloxanide furoate 500mg three times a day for 10 days must always be given afterwardsDoses for children are calculated by body weight and a pharmacist should be consulted for help.
Herbal treatments
In Mexico, it is common to use herbal tinctures of chaparro amargo. 30 drops are taken in a small glass of water first thing in the morning, and 30 drops before the last meal of the day, for seven days straight. After taking a seven day break from the treatment, it is resumed for seven days.
A 1998 study in Africa suggests that 2 tablespoons per week of papaya seeds may have some antiamoebic action and aid in prevention of amoebiasis, but this remains unconfirmed.
Complications
In the majority of cases, amoebas remain in the gastrointestinal tract of the hosts.
Entamoeba histolytica infection is associated with malnutrition and stunting of growth.
Populations at risk
All people are believed to be susceptible to infection, but individuals with a damaged or undeveloped immunity may suffer more severe forms of the disease.
Food analysis
E. histolytica cysts may be recovered from contaminated food by methods similar to those used for recovering Giardia lamblia cysts from feces. histolytica cysts must be distinguished from cysts of other parasitic (but nonpathogenic) protozoa and from cysts of free-living protozoa as discussed above. cysts are easily lost or damaged beyond recognition, which leads to many falsely negative results in recovery tests. (See the FDA Bacteriological Analytical Manual.)
Outbreaks
The most dramatic incident the USA was the Chicago World's Fair outbreak in 1933 caused by contaminated drinking water;
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