Another form of dysentery called amebic dysentery or intestinal amebiasis is spread by a protozoan, Entamoeba histolytica. The protozoan occurs in an active form, that which infects the bowel, and an encysted form, that which forms the source of infection. If the patient develops diarrhea the active form of amoeba will pass from the bowel and rapidly die. If no diarrhea is present the amoeba will form a hard cyst about itself and pass from the bowel to be picked up by another victim. Once ingested it will lose its shell and begin the infectious cycle. Amebic dysentery can be waterborne, so anyone drinking infested water that is not purified is susceptible to infection.
Amebic dysentery is common in the tropics and relatively rare in temperate climates. Infection may be so subtle as to be practically unnoticed. Intermittent bouts of diarrhea, abdominal pain, flatulence, and cramping mark the onset of infection. Spread of infection may occur with the organisms entering the liver, so abdominal tenderness may occur over the area of the liver. Because the amoeba invades the lining of the colon, some bleeding may occur, and in severe infections the patient may require blood transfusions to replace that which is lost.
Treatment again is aimed at replacement of lost fluids and the relief of symptoms. Microscopic examination of the stool will reveal the active protozoan or its cysts. Special medications aimed at eradicating the infectious organism may be needed.
An outbreak of amebic dysentery can occur seemingly mysteriously because the carrier of the amoeba may be without symptoms, especially in a temperate zone. This is the person with inadequate sanitation who can spread the disease through food that he has handled. Often the health officials can trace a disease outbreak back to a single kitchen and then test the cooks for evidence of amebic dysentery.
Before the idea of the spread of infectious agents was understood, dysentery often was responsible for more casualties among the ranks of armies than was actual combat. It also was a constant presence among prisoners who often died because little or no medical assistance was available to them. It is still a condition present throughout the world that requires vigilance. Prevention is the most effective means to maintain the health of populations living in close quarters. Hand washing, especially among food preparation personnel, and water purification are the most effective means of prevention. Adequate latrine facilities also help to contain any infectious human waste. A carefully administered packet of water and electrolytes to replace those lost can see a child through the infection.
See also Digestive system.