Definition & Facts
Amoebiasis is an intestinal infection caused by the parasitic protozoa, Entamoeba histolytica or E. histolytica. Amoebiasis is mostly prevalent in the tropics and the developing countries where sanitation levels are low. In these areas, barriers between water sources and sewage disposal facilities, if and when they exist, are inadequate.
Human beings carry the disease which is usually transmitted via water, food, or hands contaminated by feces. It is spread through the fecal-oral route. In some cases, transmission can occur sexually through anilingus.
Symptoms & Complaints
An asymptomatic carrier may unknowingly spread the parasite to other people. Therefore, if someone has reason to believe that they have been exposed to the parasite, they should see a medical doctor.
Symptomatic infections exhibit symptoms that can be mild or severe. Mild symptoms include:
- Diarrhea (passage of between 3-8 semi solid stools in a day, or soft stool exhibiting mucus and traces of blood)
- Excessive gas
- Pain in the rectum when moving bowel (tenesmus)
- Unintentional weight loss
- Abdominal cramps
Severe signs include:
- Tenderness in the abdomen
- Stools that are bloody, watery stools with blood streaks and frequent stool passage—between 10 and 20 times in a day.
Amoebiasis may cause several health complications like:
- Perianal ulceration (ulcers around the anal region)
- Granuloma of the colon (large intestine inflammation)
- Colitis (an inflamed lining of the colon)
- Perforation of the colon (the colon develops holes making food particles spill into the abdominal cavity)
- Liver abscess (liver inflammation and collection of infected material)
- Peritonitis (inflammation of the inner abdominal lining)
Amoebiasis results from transmission of Entamoeba histolytica through ingestion. Ingestion of the parasite happens in its cystic form when it is most infectious. The protozoa remain in the environment for weeks and even months. The cysts occur in soil contaminated with feces, fertilizers, water and contaminated hands.
When the cyst enters the body, it embeds itself in the colon. It undergoes excystation (the protozoa breaks out of the cyst). This results in trophozoites which invade walls of the colon. These then cause tissue destruction, bloody diarrhea and inflammatory disease. The trophozoites may travel through the blood and into other organs like the liver.
Some scenarios predispose people to develop the disease. Although amoebiasis exists all over the world, it is most prevalent in developing countries that face infrastructural challenges. Sewerage disposal systems and water sources sometimes intermingle causing contamination of drinking and cooking water. People traveling to these countries have to be vigilant.
Diagnosis & Tests
Doctors will try to identify the nature and cause of amoebiasis through a variety of tests. Firstly, they will perform a physical examination and ask about the patient’s medical history. Of particular interest are overseas travels to high-risk areas. The doctor will perform the following tests:
- Stool sample
- Tissue samples from inflamed areas
- Blood tests for amoebiasis
- Sigmoidoscopy (examination of the lower large intestine)
The above tests may not be conclusive, so the doctor may order other tests such as:
Treatment & Therapy
Amoebiasis can be treated with drugs like:
People diagnosed with amoebic colitis need nitroimidazole. It is followed by a luminal agent (paromomycin or diloxanide furoate), which kills immature parasites thus averting recurrence of the infection. Doctors may use metronidazole to treat amoebic liver abscess. Doctors may also use broad spectrum antibiotics if complications include perforations in the colon wall.
Surgical procedures may be an option in the event of the following:
- Perforated amoebic colitis
- Amoebic liver abscess that is especially large
- Gastrointestinal bleeding
- Toxic megacolon (enlarged colon as a result of corticosteroids)
Prevention & Prophylaxis
- Wash hands thoroughly under running water with soap after visiting the bathroom, before preparing food and before eating any meal.
- Wash hands after handling diapers.
- Inform sex partners about risks posed by sexual contact in transmission of the disease
- Infected food handlers should keep away from food
- Do not share face towels or washers
- Keep away from unpasteurized products like cheese and milk
- Clean toilets and bathrooms as often as possible
When traveling to places prone to the disease:
- Drink bottled, chlorinated or boiled water.
- Wash vegetables and fruits thoroughly before cooking and eating them
- Avoid eating uncooked meals, particularly fruits and vegetables that cannot be peeled.
- Keep away from ice cubes and fountain drinks