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The Facts on Dysentery

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.

Causes of Dysentery

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.