Entamoeba histolytica is a microscopic parasite (an amoeba) that lives in the human intestine and causes a disease called amoebiasis. People usually become infected by swallowing cysts (the parasite’s hardy form) in contaminated food or water. Once inside the gut, the cysts release active forms (trophozoites) that can feed on nutrients and invade the intestinal lining (Shirley et al., 2018).

Most infections are mild or even symptom-free, but in some people, the parasite causes diarrhoea, abdominal pain, and dysentery (diarrhoea with blood and mucus). In severe cases, E. histolytica can spread beyond the intestine and cause liver abscesses or, rarely, affect other organs. The infection is more common in areas with poor sanitation and remains a significant cause of illness and death in many low- and middle-income countries (Fotedar et al., 2007; Shirley et al., 2018).

✔️ What it is: A microscopic parasite (amoeba) that infects the human intestine and causes amoebiasis (Shirley et al., 2018).

✔️ How it spreads: By swallowing cysts in contaminated food, water, or on unwashed hands. Poor sanitation is the main risk factor (Fotedar et al., 2007).

✔️ Symptoms:

Mild cases: diarrhoea, stomach cramps, bloating, fatigue.

Severe cases: dysentery (diarrhoea with blood and mucus), fever, and abdominal pain.

Extra-intestinal cases: liver abscesses (fever, right-sided abdominal pain), rarely spread to lungs or brain (Mortimer & Chadee, 2010).

✔️ Who’s most at risk: Children, travellers to endemic regions, people in areas with poor sanitation, and immunocompromised individuals.

✔️ Treatment: Two-step therapy to first kill the active parasites, followed by a luminal agent to clear cysts to prevent reinfection (Petri & Singh, 1999).

✔️ Prevention: Wash hands with soap, drink safe or boiled water, wash fruits and vegetables, and avoid raw foods in high-risk regions.

When Entamoeba histolytica cysts are swallowed in contaminated food or water, they release active trophozoites in the intestine. These trophozoites can invade the gut lining and cause tissue damage. The innate immune system (the body’s immediate defence) responds first. Gut cells recognise the parasite and release alarm signals such as interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α), which attract neutrophils and macrophages to fight the infection (Nakada-Tsukui & Nozaki, 2016). However, E. histolytica has powerful survival strategies—it produces enzymes that break down tissue and can even kill immune cells, contributing to ulcers and diarrhoea (Mortimer & Chadee, 2010).

The adaptive immune system then provides more targeted defence. CD4+ T helper cells, especially Th1 cells, release interferon-γ (IFN-γ), which activates macrophages to destroy infected cells (Shirley et al., 2018). At the same time, antibodies such as IgA coat the parasite in the gut, preventing it from attaching to intestinal cells (Petri & Singh, 1999). Still, E. histolytica can evade some of these defences by shedding surface proteins targeted by antibodies and suppressing T cell activity (Mortimer & Chadee, 2010). In most healthy people the infection is controlled, but in some cases the parasite spreads beyond the intestine—most often to the liver—where it can form abscesses.

Many people infected with Entamoeba histolytica do not develop symptoms. However, when the parasite becomes invasive, it causes the disease known as amoebiasis. The most common intestinal symptoms are diarrhoea, abdominal cramps, bloating, and fatigue (Shirley et al., 2018). In more severe cases, the infection leads to dysentery—diarrhoea containing blood and mucus—along with painful straining during bowel movements (tenesmus) (Mortimer & Chadee, 2010).

Infections can also spread beyond the intestines. The most frequent extra-intestinal complication is a liver abscess, which causes fever, chills, loss of appetite, and pain in the upper right side of the abdomen. Rarely, the parasite may reach the lungs or brain, leading to life-threatening illness (Petri & Singh, 1999). Children, malnourished individuals, and people with weakened immune systems are at greater risk of severe, prolonged illness that can result in dehydration, weight loss, and impaired gut health (Fotedar et al., 2007).

A driver of diarrhoeal disease. In South Africa, Entamoeba histolytica is one of several amoeba species found in people attending gastroenterology clinics. A study in Giyani and Pretoria found that 8.5% of patients carried E. histolytica, while similar numbers carried non-pathogenic species like E. dispar (8%) or E. bangladeshi (4.8%). Unlike these harmless relatives, E. histolytica was strongly associated with diarrhoea and changes in gut bacteria—particularly reductions in Prevotella copri, a species linked to healthy gut function (Ngobeni et al., 2017). This shows that E. histolytica not only causes direct gut damage but also disrupts the microbiome balance.

A hidden burden in children. Across Africa, about 13.3% of school-aged children are infected with E. histolytica/dispar, making it one of the most common intestinal parasites alongside Giardia (Hajissa et al., 2022). For children in South Africa, repeated exposure increases the risk of malnutrition, stunted growth, and impaired learning, as chronic gut inflammation reduces nutrient absorption. In communities with limited sanitation and clean water, these infections contribute to the cycle of poor gut health and long-term vulnerability.

Key Takeaways

Gut disruption: E. histolytica causes diarrhoea and shifts in the gut microbiome, unlike non-pathogenic amoebae (Ngobeni et al., 2017).

Child health risks: Over 1 in 10 African schoolchildren are infected, putting them at risk of malnutrition and poor growth (Hajissa et al., 2022).

Community challenge: Poor sanitation and unsafe water allow the parasite to circulate, reinforcing the burden of gut disease in South Africa.

Entamoeba histolytica is a parasite that infects the large intestine and can cause amoebiasis, ranging from mild diarrhoea to severe dysentery and liver abscesses. Because it spreads through swallowing cysts in contaminated food or water, both gut resilience and prevention are key to protection (Shirley et al., 2018).

Strengthening the gut

A balanced gut microbiome helps block harmful organisms. Beneficial bacteria such as Lactobacillus and Bifidobacterium compete with parasites, reinforce the intestinal barrier, and activate immune responses (Mortimer & Chadee, 2010). Diets rich in fibre from whole grains, fruits, and vegetables promote these protective microbes, while good nutrition—particularly vitamins A and C and minerals like zinc—supports the immune system’s ability to fight infection (Makki et al., 2018; Nakada-Tsukui & Nozaki, 2016).

Hygiene and safe food

Because infection happens when cysts are swallowed, preventing exposure is crucial:

Wash your hands with soap before eating and after using the toilet.

Drink boiled, filtered, or bottled water in high-risk areas.

Wash fruits and vegetables thoroughly; avoid raw produce where water quality is uncertain.

Ensure safe sewage and waste disposal to stop environmental contamination.

Care during illness

If infection develops, hydration is vital to replace fluids lost through diarrhoea. Medical treatment usually involves two steps: first, taking medication to kill the active parasite in tissues, followed by a luminal agent to clear cysts from the gut and prevent relapse (Petri & Singh, 1999).

Key Takeaways

Gut microbiome protection: Healthy bacteria and fibre-rich diets support the gut lining and block harmful parasites (Mortimer & Chadee, 2010; Makki et al., 2018).

Prevention is best: Clean water, food safety, and handwashing are essential to avoid infection (Shirley et al., 2018).

Treatment needs two steps: Clearing both active parasites and gut cysts prevents ongoing infection (Petri & Singh, 1999).