Many people have spent a tropical vacation with a bad stomach bug. They might have had dysentery, a painful intestinal infection that is usually caused by bacteria or parasites. Dysentery is defined as diarrhea in which there is blood, pus, and mucous, usually accompanied by abdominal pain.
There are two main types of dysentery. The first type, amoebic dysentery or intestinal amoebiasis, is caused by a single-celled, microscopic parasite living in the large bowel. The second type, bacillary dysentery, is caused by invasive bacteria. Both kinds of dysentery occur mostly in hot countries. Poor hygiene and sanitation increase the risk of dysentery by spreading the parasite or bacteria that cause it through food or water contaminated from infected human feces.
Dysentery can have a number of causes. Bacterial infections are by far the most common causes of dysentery. These infections include Shigella, Campylobacter, E. coli, and Salmonella species of bacteria. The frequency of each pathogen varies considerably in different regions of the world. For example, shigellosis is most common in Latin America while Campylobacter is the dominant bacteria in Southeast Asia. Dysentery is rarely caused by chemical irritants or by intestinal worms.
Intestinal amoebiasis is caused by a protozoan parasite, Entamoeba histolytica. The amoeba can exist for long periods of time in the large bowel (colon). In the vast majority of cases, amoebiasis causes no symptoms - only 10% of infected individuals become ill. It is uncommon except in the world's tropical zones, where it is very prevalent. People can become infected after ingesting feces that contain somebody's excreted parasites. People are at high risk of acquiring the parasite through food and water if the water for household use isn't separated from waste water. The parasites can also enter through the mouth when hands are washed in contaminated water. If people neglect to wash properly before preparing food, the food may become contaminated. Fruits and vegetables can be contaminated if washed in polluted water or grown in soil fertilized by human waste.
The Shigella and Campylobacter bacteria that cause bacillary dysentery are found all over the world. They penetrate the lining of the intestine, causing swelling, ulcerations, and severe diarrhea containing blood and pus. Both infections are spread by ingestion of feces within contaminated food and water. If people live or travel in an area where poverty or overcrowding may interfere with good hygiene and sanitation, they are at risk of being exposed to invasive bacteria. Young children (ages 1 to 4) living in poverty are most likely to contract shigellosis, campylobacteriosis, or salmonellosis.
Having sex that involves anal contact may spread amoebic and bacillary dysentery. This is especially true if the sex included direct anal or oral contact, or oral contact with an object (e.g., fingers) that touched or was in the anus of an infected person.
Symptoms and Complications
The main symptom of dysentery is frequent near-liquid diarrhea flecked with blood, mucus, or pus. Other symptoms include:
- sudden onset of high fever and chills
- abdominal pain
- cramps and bloating
- flatulence (passing gas)
- urgency to pass stool
- feeling of incomplete emptying
- loss of appetite
- weight loss
Other symptoms may be intermittent and may include recurring low fevers, abdominal cramps, increased gas, and milder and firmer diarrhea. You may feel weak and anemic, or lose weight over a prolonged period (emaciation). Mild cases of bacillary dysentery may last 4 to 8 days, while severe cases may last 3 to 6 weeks. Amoebiasis usually lasts about 2 weeks.
Bacillary dysentery symptoms begin within 2 to 10 days of infection. In children, the illness starts with fever, nausea, vomiting, abdominal cramps, and diarrhea. Episodes of diarrhea may increase to as much as once an hour with blood, mucus, and pus in the child's stool. Vomiting may result in rapid and severe dehydration, which may lead to shock and death if not treated. Signs of dehydration include an extremely dry mouth, sunken eyes, and poor skin tone. Children and infants will be thirsty, restless, irritable, and possibly lethargic. Children may also have sunken eyes and may not be able to produce tears or urine, the latter appearing very dark and concentrated.
Complications from bacillary dysentery include delirium, convulsions, and coma. A very severe infection like this can be fatal within 24 hours. However, the vast majority of infections are self-limited and resolve spontaneously without treatment.
People with amoebic dysentery may experience other problems associated with amoebiasis. The most frequent complication results when parasites spread to the liver, causing an amoebic abscess. In this case, you would have a high fever and experience weight loss and right shoulder or upper abdominal pain. If the infection of the bowel is especially virulent, the intestinal ulcerations may lead to bowel perforation and death. The parasites may rarely spread through the bloodstream, causing infection in the lungs, brain, and other organs.
Making the Diagnosis
If a doctor suspects dysentery, a stool sample usually will be required for analysis. For bacterial infections such as shigella, the diagnosis is made by culture of the stool. Unfortunately, such cultures are not available in most developing countries and the diagnosis is made clinically on the basis of symptoms. Amoebiasis is often diagnosed by finding parasites under a microscope. An antibody blood test helps to confirm the diagnosis of amoebic dysentery or liver abscess.
The E. histolytica has an identical "twin brother," Entamoeba dispar, a harmless amoeba that looks identical to E. histolytica under the microscope. It never produces symptoms and does not require treatment. In developing countries, the distinction is not usually made - individuals found to have amoebae in their stools are treated whether or not it is clear that the infection is causing symptoms. Of those diagnosed with amoebae in their stools, 90% have the harmless E. dispar.
Treatment and Prevention
Antiparasitic medications such as metronidazole* and iodoquinol, are commonly used to treat dysentery caused by amoebiasis. Antibiotics like ciprofloxacin, ofloxacin, levofloxacin, or azithromycin are used to treat the organisms causing bacillary dysentery. People with prolonged diarrhea should consult with their doctor. If you travel, you should carry a one- to three-day self-treatment antibiotic regimen such as ciprofloxacin and use it in the case of sudden moderate-to-severe diarrheal illness. Bismuth subsalicylate (Pepto-Bismol®) can also be helpful for some travelers. In addition, use the antidiarrheal medication loperamide to slow the bowel and prevent dehydration. Consult your doctor for children under 2 years of age.
It is most important to replace the fluids lost from diarrhea. In mild cases, soft drinks, juices, and bottled water will be enough. More severe diarrhea should be treated with solutions that contain electrolytes such as potassium, salt, and sucrose. For severe diarrhea, commercial oral rehydration solutions are usually needed. These solutions are available in packets for easy travel. People should try to consume enough fluids so that clear-to-light yellow urine is produced every 3 to 4 hours. While affected with dysentery, it is better to stick to a bland diet (bananas, rice, soda crackers) and avoid milk products.
Dysentery can be prevented to some extent by practising careful personal hygiene.
People who travel to or live in areas with high rates of dysentery should follow the following advice:
- Always use a condom for any sexual activity involving anal contact and wash carefully before and after sexual activity.
- Do not eat any foods cooked in unhygienic circumstances, such as from street vendors.
- Only eat cooked foods that have been heated to a high temperature. Do not eat cooked foods that have cooled.
- Do not eat raw vegetables. Avoid species of fruits without peels. Open fruits with peels yourself.
- Drink only commercially bottled or boiled water. Do not use ice unless it has been made from purified water.
- Use only bottled or boiled water to wash and to cook food in, to wash hands, and to brush teeth.
- Consider traveling with an alcohol-based hand sanitizer.
*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.