Amoebiasis

What is amoebiasis?

Amoebiasis is a contagious intestinal infection caused by a single-celled protozoan parasite Entamoeba histolytica. Amoebiasis is more common in tropical regions,especially in areas of poor sanitation.Amoebiasis can present with symptoms or can be symptomless. It can occur in children and adults.

Amoebiasis typically occurs when one drinks or eats something contaminated with E. histolytica. Amoebiasis is also known as amoebic dysentery. Amoebiasis occurs worldwide (prevalence 10%) but predominantly occurs in tropical and developing countries. In Africa, parts of South America, Mexico and India, it is a primary health concern. 

Causes and risk factors

Causes

In the colon, E. histolytica may be present and not cause any harm to the intestine. Sometimes, it attacks the colon causing acute dysentery, chronic diarrhoea or colitis. This infection can sometimes reach the liver via blood. 

Water and food contaminated with faeces are the key reason for the spread of E. histolytica. Spread is also through ingestion of cysts and vegetable fertilised by faeces. Improper cleaning of hands and foods leads to auto-infection. Amoebiasis can also spread from one person to another by oral or rectal contact with the infected individual.

When cysts enter the body, they reside in the digestive tract. Trophozoites (an invasive form of the parasite) are released and they reproduce in the digestive tract. These trophozoites then migrate to the large intestine and burrow in the intestinal wall destroying tissues and causing colitis and bloody diarrhoea. The cysts might be released in faeces in an infected person or the cysts might travel through the blood to various organs.

Symptoms and signs

Ninety percent (90%) of people infected are asymptomatic. Only one percent (1%) may develop invasive or extraintestinal amoebiasis

Symptoms in children:

In children who have symptoms, the symptoms may appear in within days of eating food infected with Amoeba or the symptoms might not appear for months or years. The symptoms may include:

  • Abdominal pain- Pain (crampy pain) begins gradually and then increases
  • Loose and watery stools
  • Nausea and vomiting
  • Loss of appetite
  • Fever
  • Blood in stools

Symptoms in Adults:

Often infected individuals do show symptoms. Symptoms are evident only after a week or 4 weeks post infection by the parasite.

Milder symptoms of amoebiasis include:

  • Diarrhoea: Passage of soft or semi-formed stools/day, 3-8 times, sometimes with blood.
  • Cramps in the abdomen
  • Fatigue
  • Pain in the rectum with bowel movement
  • Flatulence
  • Unintentional loss of weight

Severe symptoms of amoebiasis include:

  • Stools with blood (liquid stools with blood patches, 10-20 stools/day)
  • Vomiting
  • Fever

Diagnosis

History taking- Usually a history of travel is asked as Amoebiasis is common in travellers.

Faecal samples are analysed for the presence of E. histolytica.  Several screenings of the faecal samples may be required, as the parasite may not be present in all the faecal samples.

Other amoeba and E. dispar may appear like E. histolytica on microscopic examination sometimes. E. dispar is not responsible for this sickness and doesn’t require treatment. Often it is difficult for many labs to differentiate between the two species.

The large bowel’s lower part may be examined internally (sigmoidoscopy).

A blood test may be recommended only if the physician suspects the infection to have spread beyond the gut (intestine).  Blood tests are not meant for diagnosis of the current infection as the result will show up positive, if one had amoebiasis earlier though one may not be infected.Liver function tests are required if the physician suspects that your liver is damaged by Amoebiasis. Serology and Polymerase Chain Reaction (PCR) are used for the extra-intestinal disease.

Treatment and prevention

Treatment

Amoebiasis is treated by use of antibiotics. After a course of antibiotics, faecal samples are assessed for the clearance of the infection.

Intravenous administration of antibiotics is advised  if you have severe vomiting

Medications to stop diarrhoea are not prescribed as a routine as it can aggravate the situation.

Surgery is required when there is damage to internal organs by the parasite.

Prevention

  • Food items should be thoroughly washed before eating especially fruits and vegetables
  • Drink pure water by boiling it or treating it with iodine
  • Dairy products like milk cheese etc. should be avoided
  • Do not eat food sold on street
  • Wash your hands properly after going to toilet

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Complications

Amoebiasis can lead to complications by the spread of the parasite to other parts of the body like lungs, brain, liver through blood. If the cysts invade the infected person bloodstream, they may cause an abscess, haemorrhages and infections leading to the death of the individual.

Next Steps

Please visit your doctor If you or the child is suffering from:

  • Diarrhoea with mucous or blood
  • Fever
  • Abdominal pain
  • Loss of Appetite

Red Flags

Please contact your doctor immediately if Amoebiasis has spread and invaded your internal organs, and symptoms are:

  • Stools with blood (liquid stools with blood patches, 10-20 stools/day)
  • Vomiting
  • High Fever
  • Severe Pain in the abdomen

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References

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  • Amebiasis. U.S. National Library of Medicine MedlinePlus. Accessed 16 Feb. 16. https://www.nlm.nih.gov/medlineplus/ency/article/000298.htm
  • Amoebiasis. World Health Organization. Accessed 16 Feb. 16. http://www.who.int/ith/diseases/amoebiasis/en/
  • Parasites – Amebiasis – Entamoeba histolytica Infection. Accessed 16 Feb. 16: Centers for Disease Control and Prevention. http://www.cdc.gov/parasites/amebiasis/general-info.html

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