Dysentery

Dysentery is an infectious disease that has ravaged armies, refugee camps, and prisoner-of-war camps throughout history. The disease still is a major problem in developing countries with primitive sanitary facilities.

The acute form of dysentery, called shigellosis or bacillary dysentery, is caused by the bacillus (bacterium) of the genus Shigella, which is divided into four subgroups and distributed worldwide. Type A, Shigella dysenteriae, is a particularly virulent species. Infection begins from the solid waste from someone infected with the bacterium. Contaminated soil or water that gets on the hands of an individual often is conveyed to the mouth, where the person contracts the infection. Flies help to spread the bacillus.

Young children living in primitive conditions of overcrowded populations are especially vulnerable to the disease. Adults, though susceptible, usually will have less severe disease because they have gained a limited resistance. Immunity as such is not gained by infection, however, and an infected person can become reinfected by the same species of Shigella.

Once the bacterium has gained entrance through the mouth, it travels to the lower intestine (colon) where it penetrates the mucosa (lining) of the intestine. In severe cases, the entire colon may be involved, but usually only the lower half of the colon is involved. The incubation period is one to four days, that is the time from infection until symptoms appear.

Symptoms may be sudden and severe in children. They experience abdominal pain or distension, fever, loss of appetite, nausea, vomiting, and diarrhea. Blood and pus will appear in the stool, and the child may pass 20 or more bowel movements a day. Left untreated, he will become dehydrated from loss of water and will lose weight rapidly. If untreated, death may occur within 12 days of infection. If treated or if the infection is weathered, the symptoms will subside within approximately two weeks.

Adults experience a less severe course of disease. They will initially feel a griping pain in the abdomen, develop diarrhea, though without any blood in the stool at first. Blood and pus will appear soon, however, as episodes of diarrhea recur with increasing frequency. Dysentery usually ends in the adult within four to eight days in mild cases, and up to six weeks in severe infections.

Shigella dysenteriae brings about a particularly virulent infection that can be fatal within 12 to 24 hours. The patient has little or no diarrhea, but experiences delirium, convulsions, and lapses into a coma. Fortunately, infection with this species is uncommon.

Treatment of the patient with dysentery usually is by fluid therapy to replace the liquid and electrolytes lost in sweating and diarrhea. Antibiotics may be used, but some Shigella species have developed resistance to them, and in these cases, antibiotics may be relatively ineffective.

Some individuals harbor the bacterium without having symptoms. Like those who are convalescent from the disease, the carriers without symptoms can spread the disease. This may occur by someone with improperly washed hands preparing food, which becomes infected with the organism.

Another form of dysentery called amebic dysentery or intestinal amebiasis is spread by a protozoan, Entamoeba histolytica. The protozoan occurs in an active form, which infects the bowel, and an encysted form, 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 lost blood.

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. A person with inadequate sanitation can spread the disease through food that he has handled. Often, 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. Dysentery remains 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.

See also Waste water treatment; Water pollution and purification; Water quality