What is Dysentery?

By Liji Thomas, MD

Dysentery is an infection of the intestines which causes the passage of bloody stools mixed with mucus. It is caused either by bacteria such as Shigella, or by parasites such as Entamoeba. These forms are called bacillary dysentery, or shigellosis, and amoebic dysentery respectively.

Other symptoms of dysentery include cramps, bloating, and fever, along with 3-8 soft or liquid stools a day. In more severe cases there may be pain on touching the abdomen, severe diarrhea  evidenced by 10 or more stools a day, nausea or vomiting. Fever may rise as high as 100.4 F (38oC). Very young children, below 5 years, may not show such a high rise in temperature. There may also be fatigue, rectal pain during stool passage, and loss of weight without any significant cause. Most cases clear up in a week or less. If symptoms persist, medical care is needed.

The symptoms of amoebic dysentery may range from abdominal pain, bloating and flatulence to chronic diarrhea. Entamoeba histolytica is a tiny shapeless parasite which can live in the intestine with or without causing symptoms. The parasites sometimes enter the bloodstream and spread to the liver, or rarely, to the brain or the lungs, causing abscess formation.

Symptoms of amoebic dysentery occur within 7 to 28 days of infection. Most infections, however, are asymptomatic and do not cause any problems. Shigella infection causes symptoms within 1-3 days, or up to 7 days. The most severe form is due to Shigella dysenteriae.  Other species include S. flexneri, S. boydii and S. sonnei.

The bacteria or parasites are usually transmitted via the fecal-oral route. The vector could be a housefly or other pest, or a food handler might have an undiagnosed infection and neglect proper hand hygiene procedures.  Poor sanitation is a leading cause of transmission in low-income areas and regions.  Another route is the use of untreated human waste as fertilizer. Composting destroys the amoeba in all its forms, and renders the waste suitable for use.

Groups of people in close contact, such as students in school, a playgroup or a family, are more prone to picking up the infection from each other.

Homosexual anal contact or oral-anal sex is another way to transmit the infection.

Risk factors

  • Alcoholism
  • Poor nutrition
  • Malignancies
  • Vulnerable ages such as old people or young children
  • Medication such as steroids which weaken immunity
  • Pregnancy
  • Travel in a place with high prevalence of infection

Complications of dysentery include:

  • Dehydration
  • Malnutrition
  • Liver abscess
  • Brain or lung abscess
  • Chronic dysentery
  • Weakened immunity and susceptibility to other infections
  • Anemia
  • Toxic dilatation of the large intestine
  • Acute kidney failure or disease

Diagnosis and treatment

Diagnosis is based on a history of possible contact with the parasite or bacteria, such as travel abroad, confirmed by other tests:

  • Blood tests for Entamoeba or Shigella
  • Stool tests
  • Microscopy for the presence of the parasite or bacteria
  • Sigmoidoscopy, which means an endoscopic examination of the inside of the large intestine where the parasite is usually found.

The management of dysentery includes:

  • Plenty of oral fluids, such as clean coconut water, plain water, and oral rehydration solution (ORS), to avoid dehydration
  • Paracetamol for pain and fever
  • Stopping the diarrhea with drugs like loperamide is not advisable, since it may lead to further worsening of the condition
  • Medicines for vomiting may be given to help you take required medication by mouth, rather than by injection
  • Once the condition resolves, a re-examination of the stool is necessary to confirm that the infection has been eradicated.
  • In severe cases of Shigellosis, a short course of antibiotics may be needed to eradicate the infection.
  • In most cases of amoebic dysentery, antibiotics are necessary to avoid the development of a recurrent or chronic infection.


  • Careful hand washing after contact with potentially infected surfaces or people
  • Hand washing before and after eating or handling food, before and after you visit the bathroom, and before you touch surfaces in common use
  • Use separate towels
  • Disinfect toilets after use if a person in the family or group has dysentery
  • Wash all laundry which has come into contact with an infected person in very hot water
  • Avoid crowded settings , or food handling, childcare and health care, during and at least 48 hours after the infection has resolved
  • Either eat food hot, or within 2 hours of preparation
  • Keep cooked food below 4 C or above 60 C, and separate raw and cooked foods to avoid cross-contamination
  • Test other people in the environment if repeated outbreaks occur without an obviously infected person. Make sure such asymptomatic carriers do not handle food, feed or otherwise take care of children or handle anything to do with them.

When in endemic areas, avoid the following:

  • Raw fruits or vegetables, unless you can peel them and then wash your hands
  • Ice in your water or drink
  • Water which has not been boiled and cooled, or which is not sealed
  • If you have to drink tap water, use chlorine tablets to disinfect it first
  • Raw or cold seafood such as prawns or shellfish
  • Unpasteurized milk, ice cream and other milk products
  • The use of sodium hypochlorite generators to produce this chemical to sterilize public and private water supplies has had great effect on halving the rate of waterborne diseases such  as dysentery


Last Updated: Sep 8, 2015

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