10% of the global population is thought to be affected

40,000 to 100,000 deaths every year worldwide


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What are the causes?

Amebiasis is caused by the amoeba Entamoeba histolytica, a parasite specific to humans. This protozoan can surround itself with a thin shell to form a cyst measuring a few microns in diameter. When these cysts are ingested, they germinate in the small intestine and pass to the vegetative state, trophozoites, before traveling to the large intestine, where they multiply and revert to cysts. It is in the more resistant cyst form that E. histolytica is excreted in feces and may infect other people.

How is the parasite transmitted?

Humans are the only reservoir for the intestinal parasite Entamoeba histolytica. The parasite is eliminated in the form of "cysts" in stools, which can resist for up to several weeks in warm, damp outdoor environments.

Infection mainly occurs in regions with poor sanitation.
The parasite is transmitted by the fecal–oral route, in other words usually by ingesting contaminated water or food, or via dirty hands or objects soiled by excreta containing amoebic cysts.
Flies and cockroaches may occasionally serve as mechanical carriers of cysts (from feces to food). Geophagy (consuming soil, a practice that is widespread in some cultures) may sometimes be a source of infection.

The transmission and proliferation of the amoebae that cause amebiasis, facilitated by poor hygiene conditions, make this neglected disease a major public health problem.

What are the symptoms?

Once ingested, the parasitic cysts release generally non-pathogenic amoebae into the intestine. Nearly 90% of carriers are asymptomatic.

In a small number of infected individuals, the parasite can penetrate the colonic mucosa. When they cross the mucosa, the amoebae trigger intestinal amebiasis or amoebic dysentery.

The clinical profile is similar to that of shigellosis, the main cause of dysentery. Amebiasis may cause symptoms ranging from mild diarrhea to painful, bloody diarrhea (dysentery with blood and mucus in the stools). The destruction of the intestinal wall can then lead to the formation of ulcers.

If the parasite reaches the bloodstream, it can infect the liver and result in abscesses, which are fatal if left untreated. The disease can also lead to other local complications, like abscesses in the lungs or, much more rarely, in the brain.

How is amebiasis diagnosed?

Several diagnostic techniques can be used:

  • Stool microscopy (to confirm the presence of the parasite in stools);
  • Serological assay;
  • Detection of parasite DNA in stools;
  • Imaging in the event of extra-intestinal infection.

Effective diagnosis of cysts is vital given the continued transmission and proliferation of amoebae, a situation exacerbated by poor sanitation in the most affected countries.

What treatments are available?

Acute amebiasis is treated by taking broad-spectrum antiparasitics and luminal amebicides, such as metronidazole or tinidazole, which act locally in the bowel lumen.

Drugs used to clear cysts, such as paromomycin and iodoquinol, can also be taken.

In regions where amebiasis is not endemic, WHO also recommends treating asymptomatic carriers with luminal amebicides to reduce the risk of transmission.

How can amebiasis be prevented?

Although the effectiveness of available antiparasitic treatments is recognized, the use of such non-specific drugs raises the risk that resistance will develop in the various pathogens that they target.

Prevention therefore has a key role to play in tackling amebiasis, especially in view of the ongoing transmission and proliferation of the parasite, a situation exacerbated by poor sanitation.

The aim of prevention is to reduce the transmission of cysts. It is primarily based on eliminating traces of feces from water, food and hands, and on developing diagnostic methods that can reveal the presence of cysts, also in asymptomatic carriers.

How many people are affected?

Around 10 to 20% of infected individuals develop severe amebiasis symptoms. Every year, 40,000 to 100,000 people die from the disease, mainly in poor regions with a warm climate, especially in South-East Asia, South-East and West Africa, Central America and South America, where poor hygiene conditions and a lack of reliable wastewater treatment systems can encourage the circulation and transmission of amoebae. In some regions of India, Mexico, Bangladesh and South Africa, the proportion of people infected may be as high as 20%. In developed countries, the disease is more rare; sporadic cases recorded are imported by travelers returning from endemic regions.
Infection mainly occurs in regions with poor sanitation.

March 2024

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