Introduction – Amoebiasis (Amoebic Dysentery)

Dysentery term refers is infectious diarrhea, Inflammation of the intestines characterized by bloody diarrhoea.

Dysentery is an intestinal inflammation, primarily affects colon. It can begin to mild or severe stomach cramps and severe diarrhea with mucus or blood in the stool. Without adequate hydration, it can be deadly.

Types of Dysentery

There are the two major types of dysentery –

1. Amoebic dysentery or or intestinal amoebiasis

2. Bacillary dysentery or or shigellosis

Bacillary dysentery

Bacillary and amoebic dysentery are both highly infectious. Bacillary dysentery, also called shigellosis, is caused by bacteria bacilli of the genus Shigella.

Amoebic dysentery

Amoebic dysentery is parasitic infection, caused by protozoan parasite Entamoeba histolytica. Amoebiasis or amoebic dysentery is a infection of human gastrointestinal tract, it is parasitic infection.

Amoebiasis Causative Agent

Amebiasis is an intestinal (bowel) illness. The causative agent Amoebic dysentery is protozoan parasite Entamoeba histolytica, which is spread through human feces (poop).

Amoebic dysenteric patients will suffer 6-8 episodes of loose motions per day. Those with Bacillary type will have more than 10 episodes of motions per day with blood in stool because it is Invasive intestinal parasitic infection.

If the parasite invades the lining of intestine, it can cause amoebic dysentery.

Amebic dysentery is a severe form of amoebiasis mainly associated with stomach cramps, abdominal pain, bloody stools (poop), and fever.

Rarely, Entamoeba histolytica invades the other organ such as liver and forms an abscess (a collection of pus).

Epidemiological  Triad

Agent – Amorbiasis is caused by Entamoeba Histolytica parasite. Cyst form of E. Histolytica are infective to man, it remain in feces, water, sewage and soil for several days at low temperature and moisture.

Host factor–  Amoebiasis can occur at any age

Environmental Factor– Poor sanitation, low socio- economic status, higher rate during rainy season.

Mode of Transmission

Portal of entry – faeco- oral route

1. Transmits through faeco- oral route

2. By Sexual route – transmits the infection by oral-rectal contact

3. By vector – Flies, cockroaches etc are the vectors which capable to carry cyst and contaminating the food.

Pathophysiology of  Amoebic Dysentery

Amoebiasis is mainly transmitted by the fecal-oral route by consuming contaminated food and water . It can also be spread indirectly through contact with dirty hands or objects as well as by anal-oral contact.

1. Infection is spread through ingestion of the cyst form of the parasite, a semi-dormant and hardy structure found in poop; feces.

2. Parasite enters into the Gastrointestinal track cause tissue destruction induced by the E. histolytica parasite. 

3. E. histolytica causes tissue destruction and damage by three main events – direct host cell killing, inflammation, and parasite invasion.

4. E. Histolytica  invade the mucosal lining of intestine

5. Amoebae invading the lining of the colon and blood come from bleeding lesions

6. Parasite also invades the other organ of body such as live and form cysts

Non-encysted amoebae, or trophozoites form of E. Histolytica  , die quickly after leaving the body but may also be present in human stool.

And then amoebiasis is transmitted through ingesting contaminated food and water with parasite.

Traveler’s Diarrhea

Amoebic dysentery is one form of traveler’s diarrhea. Amoebiasis, a type of gastro infection, is a cause of diarrhoea among travellers.

Incubation Period

The incubation period is usually 2 to 4 weeks

Period of communicability 

Cases are infectious as long as cysts are present in the faeces.

Clinical Manifestation

Infection caused by Entamoeba histolytica may be asymptomatic. For patients who develop amoebic dysentery, symptoms are –

1. Abdominal pain

2. Abdominal discomfort/ abdominal cramping

3. Loose stool/ Diarrhoea – diarrhea, or bloody diarrhea; passage of 3 to 8 semiformed stools per day, or passage of soft stools with mucus and occasional blood

4. Nausea and vomiting

5. Fever

6. Lethargy

7. Unintentional weight loss

8. Colonic ulcerations

9. Fatigue

10. Rectal pain while having a bowel movement (tenesmus)

In asymptomatic infections, the amoeba lives by eating and digesting bacteria and food particles in the gut, a part of the gastrointestinal tract.

Disease occurs when amoeba comes in contact with the cells lining the intestine lead to penetration and digestion of human tissues, resulting first in flask-shaped ulcerations in the intestine.

Laboratory Diagnosis

1. Indirect hemagglutination assay (IHA)

2. Counter immunoelectrophoresis (CIEP)

3. ELISA – Enzyme-linked immunosorbent assay

4. Blood test

5. Examination of stool samples

6. Occult blood test

7. Microscopic identification of cysts and trophozoites in the stool –  for diagnosing E. histolytica. This test can be done using – Fresh stool; wet mounts and permanently stained preparations.

8. Antibody IgG  test – useful in identification of amoebic dysentery and differentiating Amoebiasis from other causes of liver cysts and pancreatic infection. 

9. Amoebiasis test – blood test conducted to determine the level of parasitic infection of the intestines caused by entamoeba histolyca.

Treatment of Amoebic Dysentery

 
Gastrointestinal amebiasis or Amebic dysentery is treated with nitroimidazole, metronidazole and tinidazole drugs.

Nitroimidazole drugs, kill amoebas in the blood, in the wall of the intestine and in liver abscesses. These drugs include.

Drug of Choice – Metronidazole drug often use for the treatment of amoebic dysentery in adults and children.

Asymptomatic cases – in Asymptomatic cases, should be treated with diiodohydroxyquin or Diloxanide Furoate.

Prevention and Control

1. Early diagnosis and treatment

2. Safe disposal of human excreta

3. Handwashing with soap before eating

4. Handwashing with soap after the toilet

5. Safe water supply

6. Prevention of food contamination

Complications of Amoebic Dysentery

Complications of amoebic dysentery can include –

1. Peritonitis

Inflammation and ulceration of the colon with tissue death or perforation, which may result in peritonitis.

2. Anemia

People affected with amebiasis may develop anemia due to prolonged gastric bleeding

3. Amoebic liver abscesses

If the parasite once reaches into the bloodstream, it can spread through the body, such as liver where it can form liver cysts and cause amoebic liver abscesses.

What is the difference between Amoebic Dysentery and Bacillary Dysentery?

Dysentery can be results from viral, bacterial, or protozoan infections or parasitic infestations.

Amoebic dysentery (amebiasis) results from a parasite infection, caused by an amoeba called Entamoeba histolytica. 

Amoebic dysentery or intestinal amoebiasis or amebiasis is  microscopic parasite living in the gastrointestinal track; large bowel.

Bacillary dysentery is a type of dysentery results from bacteria Shigella and disease is called shigellosis. Bacillary dysentery, is caused by invasive bacteria.