Amoebiasis/Amebiasis (Amoebic Dysentery) Case Study


Amoebiasis protozoal infection of human beings initially involves the colon, but may spread to soft tissues, most commonly to the liver or lungs, by contiguity or hematogenous or lymphatic dissemination.

Amoebiasis is the third leading parasitic cause of death worldwide, surpassed only by malaria and schistosomiasis. On a global basis, amoebiasis affects approximately 50 million persons each year, resulting in nearly 100,000 deaths.

Etiologic Agent:

Enatamoeba Histolytica

  • Prevalent in unsanitary areas
  • Common in warm climate
  • Acquired by swallowing
  • Cysts survives a few days outside of the body
  • Cyst passes to the large intestine and hatch into trophozoites. It passes into the mesenteric veins, to the portal vein, to the liver, thereby forming amoebic liver abscess.

Entamoeba Histolytica has two developmental stages:

  1. Trophozoites/vegetative form
    • Trophozoites are facultative parasites that may invade the tissues or may be found in the parasitized tissues and liquid colonic contents.
  2. Cyst
    • Cyst is passed out with formed or semi-formed stools and are resistant to environmental conditions.
    • This is considered as the infective stage in the cycle of E. histolytica

Source: Human Excreta

Incubation Period: The incubation period in severe infection is three days. In subacute and chronic form it lasts for several months. In average cases the incubation period varies from three to four weeks

Period of Communicability: The microorganism is communicable for the entire duration of the illness.

Modes of Transmission:

  1. The disease can be passed from one person to another through fecal-oral transmission.
  2. The disease can be transmitted through direct contact, through sexual contact by orogenital, oroanal, and proctogenital sexual activity.
  3. Through indirect contact, the disease can infect humans by ingestion of food especially uncooked leafy vegetables or foods contaminated with fecal materials containing E. histolytica cysts.

Food or drinks maybe contaminated by cyst through pollution of water supplies, exposure to flies, use of night soil for fertilizing vegetables, and through unhygienic practices of food handlers.

Clinical Manifestations:

  1. Acute amoebic dysentery
    • Slight attack of diarrhea, altered with periods of constipation and often accompanied by tenesmus.
    • Diarrhea, watery and foul smelling stool often containing blood-streaked mucus
    • Colic and gaseous distension of the lower abdomen
    • Nausea, flatulence, abdomnal distension and tenderness in the right iliac region over the colon
  2. Chronic amoebic dysentery
    • Attack dysentery that lasts for several days, usually succeeded by constipation
    • Tenesmus accompanied by the desire to defacate
    • Anorexia, weight loss, and weakness
    • Liver may be enlarged
    • The stool at first is semifluid but soon becomes watery, bloody, and mucoid
    • Vague abdominal distress, flatulence, constipation or irregularity of bowel
    • Mild toxemia, constant fatigue and lassitude
    • Abdomen loses its elasticity when picked up between fingers
    • On sigmoidoscopy, scattered ulceration with yellowish and erythematous border
    • The gangrenous type (fatal cases) is characterized by the appearance of large sloughs of intestinal tissues in the stool accompanied by hemorrhage.
  3. Extraintestinal forms
    1. Hepatic
    • Pain at the upper right quadrant with tenderness of the liver
    • Abscess may break through the lungs, patient coughs anchovy-sauce sputum
    • Jaundice
    • Intermittent fever
    • Loss of weight or anorexia

Clinical Features:

  1. Onset is gradual
  2. Diarrhea increases and stool becomes bloody and mucoid
  3. In untreated cases:

amoebiasis clinical features

Anatomy and Physiology:

Amebiasis is an intestinal illness that’s typically transmitted when someone eats or drinks something that’s contaminated with a microscopic parasite called Entamoeba histolytica (E. histolytica). The parasite is an amoeba, a single-celled organism. That’s how the illness got its name — amebiasis.

In many cases, the parasite lives in a person’s large intestine without causing any symptoms. But sometimes, it invades the lining of the large intestine, causing bloody diarrhea, stomach pains, cramping, nausea, loss of appetite, or fever. In rare cases, it can spread into other organs such as the liver, lungs, and brain.

I. Structure. The GI System digestive systemconsists of the oral structures, esophagus, stomach, small intestine, large intestine and associated structures.

A. Oral Structures include the lips, teeth, gingivae and oral mucosa, tongue, hard palate, soft palate, pharynx and salivary glands.

B. The esophagus is a muscular tube extending from the pharynx to the stomach.

1. Esophageal openings include:

a. The upper esophageal sphincter at the cricopharyngeal muscle.

b. The lower esophageal sphincter (LES), or cardiac sphincter, which normally remains closed and opens only to pass food into the stomach.

C. The Stomach is a muscular pouch situated in the upper abdomen under the liver and diaphragm. Te stomach consists of three anatomic areas: the fundus, body (i.e., corpus), and antrum (i.e., pylorus)

D. Sphincters. The LES allows food to enter the stomach and prevents reflux into the esophagus. The pyloric sphincter regulates flow of stomach contents (chyme) into the duodenum.

E. The small intestine, a coiled tube, extends from the pyloric sphincter to the ileocecal valve at the large intestine. Sections of the small intestine include the duodenum, jejunum and ileum

F. The large intestine is a shorter, wider tube beginning at the ileocecal valve and ending at the anus. The large intestine consists of three sections:

1. The cecum is a blind pouch that extends from the ileocecal valve to the vermiform appendix.

2. The colon, which is the main portion of the large intestine, is divided into four anatomic sections: ascending, transverse, descending and sigmoid.

3. The rectum extends from the sigmoid colon to the anus.

G. The ileocecal valve prevents the return of feces from the cecum into the small intestine and lies at the upper border of the cecum.

H. The appendix, which collects lymphoid tissues, arises from the cecum.

I. The GI tract is composed of five layers.

1. An inner mucosal layer lubricates and protects the inner surface of the alimentary canal.

2. A submucosal layer is responsible for secreting digestive enzymes.

3. A layer of circular smooth muscle fibers is responsible for movement of the GI tract.

4. A layer of longitudinal smooth muscle fibers also facilitates movement of the GI tract.

5. The peritoneum, an outer serosal layer, covers the entire abdomen and is composed of the parietal and visceral layers.

II. Function. The GI system performs two major body functions: digestion and elimination.

A. Digestion of food and fluid, with absorption of nutrients into the bloodstream, occurs in the upper GI tract, stomach and small intestines.

1. Digestion begins in the mouth with chewing and the action of ptyalin, an enzyme contained in saliva that breaks down starch.

2. Swallowed food passes through the esophagus to the stomach, where digestion continues by several processes.

a. Secretion of gastric juice, containing hydrochloric acid and the enzymes pepsin and lipase ( and renin in infants)

b. Mixing and churning through peristaltic action

3. From the pylorus, the mixed stomach contents (i.e. chyme) pass into the duodenum through the pyloric valve.

4. In the small intestine, food digestion is completed, and most nutrient absorption occurs. Digestion results from the action of numerous pancreatic and intestinal enzymes (e.g., trypsin, lipase, amylase, lactase, maltase, sucrase( and bile.

B. Elimination of waste products through defacation occurs in the large intestines and rectum. In the large intestine, the cecum and ascending colon absorb water and electrolytes from the now completely digested material. The rectum stores feces for elimination.


Laboratory Diagnosis:

  1. Stool exam (cyst, white and yellow pus with plenty of amoeba)
  2. Blood exam (Leukocytosis)
  3. Proctoscopy/Sigmoidoscoppy

Sigmoidoscopy Diagnosis of amoebiasis can be very difficult. One problem is that other parasites and cells can look very similar to E. histolytica when seen under a microscope. Therefore, sometimes people are told that they are infected with E. histolytica even though they are not. Entamoeba histolytica and another ameba, Entamoeba dispar, which is about 10 times more common, look the same when seen under a microscope. Unlike infection with E. histolytica, which sometimes makes people sick, infection with E. dispar does not make people sick and therefore does not need to be treated.

If you have been told that you are infected with E. histolytica but you are feeling fine, you might be infected with E. dispar instead. Unfortunately, most laboratories do not yet have the tests that can tell whether a person is infected with E. histolytica or with E. dispar. Until these tests become more widely available, it usually is best to assume that the parasite is E. histolytica.

A blood test is also available but is only recommended when your health care provider thinks that your infection may have spread beyond the intestine (gut) to some other organ of your body, such as the liver. However, this blood test may not be helpful in diagnosing your current illness because the test may still be positive if you had amoebiasis in the past, even if you are no longer infected now.


  1. Amebic colitis
    • Fulminant or necrotizing colitis
    • Toxic megacolon
    • Ameboma
    • Rectovaginal fistulas
  2. Amebic liver abscess
    • Intrathoracic or intraperitoneal rupture with or without secondary bacterial infection
    • Direct extension to pleura or pericardium
  3. Brain abscess


  1. Metronidazole (Flagyl) 800mg TID X 5 days
  2. Tetracyline 250 mg every 6 hours
  3. Ampicillin, quinolones sulfadiazine
  4. Streptomycin SO4, Chloramphenicol
  5. Lost fluid and electrolytes should be replaced

Several antibiotics are available to treat amoebiasis. Treatment must be prescribed by a physician. You will be treated with only one antibiotic if your E. histolytica infection has not made you sick. You probably will be treated with two antibiotics (first one and then the other) if your infection has made you sick.

Nursing Management:

  1. Observe isolation and enteric precaution
  2. Provide health education and instruct patient to
    • Boil water for drinking or use purified water
    • Avoid washing food from open drum or pail
    • Cover leftover food
    • Wash hands after defacation and before eating
    • Avoid ground vegetables (lettuce, carrots, and the like)

Methods of Prevention:

  1. Health education
  2. Sanitary disposal of feces
  3. Protect, chlorinate, and purify drinking water
  4. Observe scrupulous cleanliness in food preparation and food handling
  5. Detection and treatment of carriers
  6. Fly control (they can serve as vector)


Handbook of Common Communicable and infectious Disease by Dionesia Monjejar-Navales, RN, MAEd

Lippincott Review Series Medical Surgical Nursing 4th Ed

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