Overview

Amebiasis is an intestinal infection caused by the parasite Entamoeba histolytica. It is most commonly found in areas with poor sanitation, especially in developing countries. The infection occurs when a person ingests food or water contaminated with feces containing the parasite. While many infected individuals remain asymptomatic, others develop gastrointestinal symptoms ranging from mild diarrhea to severe dysentery. In some cases, the infection can spread beyond the intestines, affecting the liver and other organs. Amebiasis is preventable with proper hygiene and is treatable with medication.

Causes

The primary cause of amebiasis is infection with the protozoan parasite Entamoeba histolytica. Transmission occurs through:

• Contaminated food or water: Consuming food or drinks contaminated with fecal matter from an infected person is the most common cause.
• Person-to-person contact: Particularly through poor hand hygiene or sexual practices, especially oral-anal contact.
• Fecal-oral route: The parasite is spread by ingesting infective cysts that survive in the environment and enter the human digestive tract.

Symptoms

Symptoms of amebiasis can vary from mild to severe, and many infected individuals do not experience any symptoms. When symptoms occur, they may include:

• Mild intestinal symptoms: Loose stools, abdominal discomfort, and mild cramping.
• Severe diarrhea: Watery or bloody diarrhea (dysentery) with mucus, sometimes accompanied by severe abdominal pain.
• Fever: Low-grade fever may occur with intestinal infection, while high fever is more common in invasive disease.
• Weight loss: Prolonged infection can lead to unintentional weight loss.
• Fatigue: Due to nutrient malabsorption and persistent diarrhea.
• Extra-intestinal symptoms: In some cases, the parasite can cause liver abscesses, resulting in right upper abdominal pain, fever, and an enlarged liver.

Diagnosis

Diagnosing amebiasis involves several clinical and laboratory methods:

• Medical history and physical exam: Assessing travel history to endemic areas and evaluating gastrointestinal symptoms.
• Stool examination: Microscopic analysis to detect cysts or trophozoites of Entamoeba histolytica. Multiple samples are usually required for accuracy.
• Antigen detection tests: Enzyme immunoassays (EIA) can help distinguish E. histolytica from non-pathogenic species.
• Serology: Blood tests to detect antibodies, especially useful in cases of liver abscess.
• Imaging studies: Ultrasound or CT scans can identify liver abscesses in cases of extra-intestinal disease.
• Colonoscopy: Occasionally used to visualize ulcers or collect biopsy samples from the colon.

Treatment

Treatment for amebiasis depends on the severity and presence of symptoms:

• Asymptomatic infection: Treated with a luminal agent such as paromomycin or diloxanide furoate to eliminate cysts from the intestine.
• Symptomatic intestinal infection: Treated with metronidazole or tinidazole to kill invasive trophozoites, followed by a luminal agent to clear residual cysts.
• Liver abscess: Treated with metronidazole or tinidazole; large abscesses may require drainage.
• Supportive care: Includes hydration, nutritional support, and managing electrolyte imbalances in severe cases.
• Avoidance of anti-diarrheal medications: These should be avoided during active infection as they can worsen symptoms.

Prognosis

With timely diagnosis and appropriate treatment, the prognosis for amebiasis is generally excellent:

• Full recovery: Most individuals recover completely with no lasting effects after treatment.
• Risk of complications: Without treatment, the infection can lead to severe dehydration, perforation of the intestines, or liver abscesses, which can be life-threatening.
• Preventable disease: Good hygiene, safe drinking water, and proper sanitation effectively prevent amebiasis.
• Low recurrence risk: Once treated, recurrence is uncommon unless re-exposed to contaminated food or water.

Overall, early treatment ensures rapid symptom resolution and reduces the risk of serious complications associated with amebiasis.