The most common type of dysentery is caused by the Shigella bacillus.
Without adequate hydration, it can be fatal.
Infection with the Shigella bacillus, or bacterium, is the most common cause.
In the United States (U.S.), signs and symptoms are normally mild and usually disappear within a few days. Most people will not seek medical attention.
If a person seeks medical help for dysentery in the U.S., however, the authorities must be informed. It is a notifiable disease.
Each year worldwide, there are between 120 million and 165 million cases of Shigella infection, of which 1 million are fatal. Over 60 percent of these fatalities are children under 5 years old in developing countries.
- Dysentery is an infection of the intestinal tract.
- Symptoms include stomach cramps and diarrhea.
- Many people have mild symptoms, but dysentery can be fatal without adequate hydration.
Here are some key points about dysentery. More detail is in the main article.
The World Health Organization (WHO) identifies two main types of dysentery.
Bacillary dysentery, or shigellosis
This type produces the most severe symptoms. It is caused by the Shigella bacillus.
Poor hygiene is the main source. Shigellosis can also spread because of tainted food.
In Western Europe and the U.S., it is the most common type of dysentery in people who have not visited the tropics shortly before infection.
Amoebic dysentery, or amoebiasis
This type is caused by Entamoeba histolytica (E. histolytica), an amoeba.
The amoebae group together to form a cyst, and these cysts emerge from the body in human feces.
In areas of poor sanitation, the amoebae can contaminate food and water and infect other humans, as they can survive for long periods outside the body.
They can also linger on people's hands after using the bathroom. Good hygiene practice reduces the risk of spreading infection.
It is more common in the tropics, but it sometimes occurs in parts of rural Canada.
Other causes include a parasitic worm infection, chemical irritation, or viral infection.
Signs and symptoms
Symptoms include diarrhea and stomach cramps.
The symptoms of dysentery range from mild to severe, largely depending on the quality of sanitation in the areas where infection has spread.
In developed countries, signs and symptoms of dysentery tend to be milder than in developing nations or tropical areas.
Mild symptoms include:
- a slight stomach-ache
These usually appear from 1 to 3 days after infection, and the patient recovers within a week.
Some people also develop lactose intolerance, which can last for a long time, sometimes years.
Symptoms of bacillary dysentery
Symptoms tend to appear within 1 to 3 days of infection. There is normally a mild stomach ache and diarrhea, but no blood or mucus in the feces. Diarrhea may be frequent to start with.
Less commonly, may be:
- blood or mucus in the feces
- intense abdominal pain
Often, symptoms are so mild that a doctor's visit is not required, and the problem resolves in a few days.
Symptoms of amoebic dysentery
A person with amoebic dysentery may have:
- abdominal pain
- fever and chills
- nausea and vomiting
- watery diarrhea, which can contain blood, mucus, or pus
- the painful passing of stools
- intermittent constipation
If amoeba tunnel through the intestinal wall, they can spread into the bloodstream and infect other organs.
Ulcers can develop. These may bleed, causing blood in stools.
Symptoms may persist for several weeks.
The amoebae may continue living within the human host after symptoms have gone. Then, symptoms may recur when the person's immune system is weaker.
Treatment reduces the risk of the amoebae surviving.
The doctor will ask the patient about their signs and symptoms and carry out a physical examination.
A stool sample may be requested, especially if the patient has recently returned from the tropics.
Fluids, and especially water, are essential to prevent dehydration.
Laboratory results will reveal whether the infection is due to Shigella or Entamoeba histolyca infection.
If treatment is necessary, it will depend on these results.
However, any patient with diarrhea or vomiting should drink plenty of fluids to prevent dehydration.
If they are unable to drink, or if diarrhea and vomiting are profuse, intravenous (IV) fluid replacement may be necessary. The patient will be placed on a drip and monitored.
Treatment for mild bacillary dysentery
Mild bacillary dysentery, the kind commonly found in developed countries with good sanitation, will normally resolve without treatment.
However, the patient should drink plenty of fluids.
In more severe cases, antibiotic drugs are available.
Treatment for amoebic dysentery
Amoebicidal medications are used to treat Entamoeba histolyca. These will ensure that the amoeba does not survive inside the body after symptoms have resolved.
Flagyl, or metronidazole, is often used to treat dysentery. It treats both bacteria and parasites.
If lab results are unclear, the patient may be given a combination of antibiotic and amoebicidal medications, depending on how severe their symptoms are.
Complications of dysentery are few, but they can be severe.
Dehydration: Frequent diarrhea and vomiting can quickly lead to dehydration. In infants and young children, this can quickly become life-threatening.
Liver abscess: If amoebae spread to the liver, an abscess can form there.
Postinfectious arthritis: Joint pain may occur following the infection.
Patients have also experienced seizures after infection.
Dysentery mostly stems from poor hygiene.
To reduce the risk of infection, people should wash their hands regularly with soap and water, especially before and after using the bathroom and preparing food.
This can reduce the frequency of Shigella infections and other types of diarrhea by up to 35 percent.
Other steps to take when the risk is higher, for example, when traveling, include:
- Only drink reliably sourced water, such as bottled water
- Watch the bottle being opened, and clean the top of the rim before drinking
- Make sure food is thoroughly cooked
It is best to use purified water to clean the teeth, and avoid ice cubes, as the source of the water may be unknown.