• <div class="section1"> Definition

    Dysentery is a general term for a group of gastrointestinal disorders characterized by inflammation of the intestines, particularly the colon. Characteristic features include abdominal pain and cramps, straining at stool (tenesmus), and frequent passage of watery diarrhea or stools containing blood and mucus. The English word dysentery comes from two Greek words meaning “ill” or “bad” and “intestine.”

    It should be noted that some doctors use the word “dysentery” to refer only to the first two major types of dysentery discussed below, while others use the term in a broader sense. For example, some doctors speak of schistosomiasis, a disease caused by a parasitic worm, as bilharzial dysentery, while others refer to acute diarrhea caused by viruses as viral dysentery.


    Dysentery is a common but potentially serious disorder of the digestive tract that occurs throughout the world. It can be caused by a number of infectious agents ranging from viruses and bacteria to protozoa and parasitic worms; it may also result from chemical irritation of the intestines. Dysentery is one of the oldest known gastrointestinal disorders, having been described as early as the Peloponnesian War in the fifth century B.C.. Epidemics of dysentery were frequent occurrences aboard sailing vessels as well as in army camps, walled cities, and other places in the ancient world where large groups of human beings lived together in close quarters with poor sanitation. As late as the eighteenth and nineteenth centuries, sailors and soldiers were more likely to die from the “bloody flux” than from injuries received in battle. It was not until 1897 that a bacillus (rod-shaped bacterium) was identified as the cause of one major ty! pe of dysentery.

    Dysentery in the modern world is most likely to affect people in the less developed countries and travelers who visit these areas. According to the Centers for Disease Control and Prevention (CDC), most cases of dysentery in the United States occur in immigrants from the developing countries and in persons who live in inner-city housing with poor sanitation. Other groups of people at increased risk of dysentery are military personnel stationed in developing countries, frequent travelers, children in day care centers, people in nursing homes, and men who have sex with other men.

    Causes and symptoms

    The most common types of dysentery and their causal agents are as follows:

    • Bacillary dysentery. Bacillary dysentery, which is also known as shigellosis, is caused by four species of the genus Shigella: S. dysenteriae, the most virulent species and the one most likely to cause epidemics; S. sonnei, the mildest species and the most common form of Shigella found in the United States; S. boydii; and S. flexneri. S. flexneri is the species that causes Reiter’s syndrome, a type of arthritis that develops as a late complication of shigellosis. About 15,000 cases of shigellosis are reported to the CDC each year for the United States; however, the CDC maintains that the true number of annual cases may be as high as 450,000, since the disease is vastly underreported. About 85 percent of cases in the United States are caused by S. sonnei. Th! e Shigella organisms cause the diarrhea and pain associated with dysentery by invading the tissues that line the colon and secreting an enterotoxin, or harmful protein that attacks the intestinal lining.
    • Amebic dysentery. Amebic dysentery, which is also called intestinal amebiasis and amebic colitis, is caused by a protozoon, Entamoeba histolytica. E. histolytica, whose scientific name means “tissue-dissolving,” is second only to the organism that causes malaria as a protozoal cause of death. E. histolytica usually enters the body during the cyst stage of its life cycle. The cysts may be found in food or water contaminated by human feces. Once in the digestive tract, the cysts break down, releasing an active form of the organism called a trophozoite. The trophozoites invade the tissues lining the intestine, where they are usually excreted in the patient’s feces. They sometimes penetrate the lining itself, however, and enter the bloodstream. If that happens, the trophozoites may be carried to the liver, lung, or other organs. Involvement of the liver or other organs is sometimes! called metastatic amebiasis.
    • Balantidiasis, giardiasis, and cryptosporidiosis. These three intestinal infections are all caused by protozoa, Balantidium coli, Giardia lamblia, and Cryptosporidium parvum respectively. Although most people infected with these protozoa do not become severely ill, the disease agents may cause dysentery in children or immunocompromised individuals. There are about 3500 cases of cryptosporidiosis reported to the CDC each year in the United States, and about 22,000 cases of giardiasis.
    • Viral dysentery. Viral dysentery, which is sometimes called traveler’s diarrhea or viral gastroenteritis, is caused by several families of viruses, including rotaviruses, caliciviruses, astroviruses, noroviruses, and adenoviruses. There are about 3.5 million cases of viral dysentery in infants in the United States each year, and about 23 million cases each year in adults. The CDC estimates that viruses are responsible for 9.2 million cases of dysentery related to food poisoning in the United States each year. Whereas most cases of viral dysentery in infants are caused by rotaviruses, caliciviruses are the most common disease agents in adults. Noroviruses were responsible for about half of the outbreaks of dysentery on cruise ships reported to the CDC in 2002.
    • Dysentery caused by parasitic worms. Both whipworm (trichuriasis) and flatworm or fluke (schistosomiasis) infestations may produce the violent diarrhea and abdominal cramps associated with dysentery. Schistosomiasis is the second most widespread tropical disease after malaria. Although the disease is rare in the United States, travelers to countries where it is endemic may contract it. The World Health Organization (WHO) estimates that about 200 million people around the world carry the parasite in their bodies, with 20 million having severe disease.


    In addition to the characteristic bloody and/or watery diarrhea and abdominal cramps of dysentery, the various types have somewhat different symptom profiles:

    • Bacillary dysentery. The symptoms of shigellosis may range from the classical bloody diarrhea and tenesmus characteristic of dysentery to the passage of nonbloody diarrhea that resembles the loose stools caused by other intestinal disorders. The high fever associated with shigellosis begins within one to three days after exposure to the organism. The patient may also have pain in the rectum as well as abdominal cramping. The acute symptoms last for three to seven days, occasionally for as long as a month. Bacillary dysentery may lead to two potentially fatal complications outside the digestive tract: bacteremia (bacteria in the bloodstream), which is most likely to occur in malnourished children; and hemolytic uremic syndrome, a type of kidney failure that has a mortality rate above 50 percent.
    • Amebic dysentery. Amebic dysentery often has a slow and gradual onset; most patients with amebiasis visit the doctor after several weeks of diarrhea and bloody stools. Fever is unusual with amebiasis unless the patient has developed a liver abscess as a complication of the infection. The most serious complication of amebic dysentery, however, is fulminant or necrotizing colitis, which is a severe inflammation of the colon characterized by dehydration, severe abdominal pain, and the risk of perforation (rupture) of the colon.
    • Dysentery caused by other protozoa. Dysentery associated with giardiasis begins about 1–3 weeks after infection with the organism. It is characterized by bloating and foul-smelling flatus, nausea and vomiting, headaches, and low-grade fever. These acute symptoms usually last for three or four days. The symptoms of cryptosporidiosis are mild in most patients but are typically severe in patients with AIDS. Diarrhea usually starts between seven and 10 days after exposure to the organism and may be copious. The patient may have pain in the upper right abdomen, nausea, and vomiting, but fever is unusual.
    • Viral dysentery. Viral dysentery has a relatively rapid onset; symptoms may begin within hours of infection. The patient may be severely dehydrated from the diarrhea but usually has only a low-grade fever. The diarrhea itself may be preceded by one to three days of nausea and vomiting. The patient’s abdomen may be slightly tender but is not usually severely painful.
    • Dysentery caused by parasitic worms. Patients with intestinal schistosomiasis typically have a gradual onset of symptoms. In addition to bloody diarrhea and abdominal pain, these patients usually have fatigue. An examination of the patient’s colon will usually reveal areas of ulcerated tissue, which is the source of the bloody diarrhea.

    Patient history and physical examination

    The physical examination in the primary care doctor’s office will not usually allow the doctor to determine the specific parasite or other disease agent that is causing the bloody diarrhea and other symptoms of dysentery, although the presence or absence of fever may help to narrow the diagnostic possibilities. The patient’s age and history are usually better sources of information. The doctor may ask about such matters as the household water supply and food preparation habits, recent contact with or employment in a nursing home or day care center, recent visits to tropical countries, and similar questions. The doctor will also need to know when the patient first noticed the symptoms.

    The doctor will also evaluate the patient for signs of dehydration resulting from the loss of fluid through the intestines. Fatigue, drowsiness, dryness of the mucous membranes lining the mouth, low blood pressure, loss of normal skin tone, and rapid heartbeat (above 100 beats per minute) may indicate that the patient is dehydrated.

    Laboratory tests

    The most common laboratory test to determine the cause of dysentery is a stool sample. The patient should be asked to avoid using over-the-counter antacids or antidiarrheal medications until the sample has been collected, as these preparations can interfere with the test results. The organisms that cause cryptosporidiosis, bacillary dysentery, amebic dysentery, and giardiasis can be seen under the microscope, as can the eggs produced by parasitic worms. In some cases repeated stool samples, a sample of mucus from the intestinal lining obtained through a proctoscope, or a tissue sample from the patient’s colon may be necessary to confirm the diagnosis. Antigen testing of a stool sample can be used to diagnose a rotavirus infection as well as parasitic worm infestations.

    The doctor will also usually order a blood test to evaluate the electrolyte levels in the patient’s blood in order to assess the need for rehydration.

    Imaging studies

    Imaging studies (usually CT scans, x rays, or ultrasound) may be performed in patients with amebic dysentery to determine whether the lungs or liver have been affected. They may also be used to diagnose schistosomiasis, as the eggs produced by the worms will show up on ultrasound or MRI studies of the liver, intestinal wall, or bladder.


    Medications are the primary form of treatment for dysentery:

    • Bacillary dysentery. Dysentery caused by Shigella is usually treated with such antibiotics as trimethoprim-sulfamethoxazole (Bactrim, Septra), nalidixic acid (NegGram), or ciprofloxacin (Cipro, Ciloxan). Because the various species of Shigella are becoming resistant to these drugs, however, the doctor may prescribe one of the newer drugs described below. Patients with bacillary dysentery should not be given antidiarrheal medications, including loperamide (Imodium), paregoric, and diphenolate (Lomotil), because they may make the illness worse.
    • Amebic dysentery. The most common drugs given for amebiasis are diloxanide furoate (Diloxide), iodoquinol (Diquinol, Yodoxin), and metronidazole (Flagyl). Metronidazole should not be given to pregnant women but paromomycin (Humatin) may be used instead. Patients with very severe symptoms may be given emetine dihydrochloride or dehydroemetine, but these drugs should be stopped once the patient’s symptoms are controlled.
    • Dysentery caused by other protozoa. Balantidiasis, giardiasis, and cryptosporidiosis are treated with the same drugs as amebic dysentery; patients with giardiasis resistant to treatment may be given albendazole (Zentel) or furazolidone (Furoxone).
    • Viral dysentery. The primary concern in treating viral dysentery, particularly in small children, is to prevent dehydration. Antinausea and antidiarrhea medications should not be given to small children. Probiotics, including Lactobacillus casei and Saccharomyces boulardii, have been shown to reduce the duration and severity of viral diarrhea in small children by 30–70 percent.
    • Dysentery caused by parasitic worms. Whipworm infestations are usually treated with anthelminthic medications, most commonly mebendazole (Vermox). Schistosomiasis may be treated with praziquantel (Biltricide), metrifonate (Trichlorfon), or oxamniquine, depending on the species causing the infestation.

    Newer drugs that have been developed to treat dysentery include tinidazole (Tindamax, Fasigyn), an antiprotozoal drug approved by the Food and Drug Administration (FDA) in 2004 to treat giardiasis and amebiasis in adults and children over the age of three years. This drug should not be given to women in the first three months of pregnancy. In addition, adults taking tinidazole should not drink alcoholic beverages while using it, or for three days after the end of treatment. The other new drug is nitazoxanide (Alinia), another antiprotozoal medication that has the advantage of lacking the bitter taste of metronidazole and tinidazole.

    Fluid replacement is given if the patient has shown signs of dehydration. The most common treatment is an oral rehydration fluid containing a precise amount of salt and a smaller amount of sugar to replace electrolytes as well as water lost through the intestines. Infalyte and Pedialyte are oral rehydration fluids formulated for the special replacement needs of infants and young children.


    Surgery is rarely necessary in treating dysentery, but may be required in cases of fulminant colitis, particularly if the patient’s colon has perforated. Patients with liver abscesses resulting from amebic dysentery may also require emergency surgery if the abscess ruptures. In some cases exploratory surgery may be needed to determine whether severe abdominal pain is caused by schistosomiasis, amebic dysentery, or appendicitis.

    Alternative treatments

    There are a number of alternative treatments for dysentery, most of which are derived from plants used by healers for centuries. Because dysentery was known to ancient civilizations as well as modern societies, such alternative systems as traditional Chinese medicine (TCM) and Ayurvedic medicine developed treatments for it.

    Ayurvedic medicine

    Ayurvedic medicine recommends fruits and herbs, specifically cumin seed, bael fruit (Aegle marmelos, also known as Bengal quince), and arjuna (Terminalia arjuna) bark for the treatment of dysentery. Ayurvedic practitioners may also give the patient dietary supplements known as Isabbael, Lashunadi Bati, and Bhuwaneshar Ras. To rehydrate the body, adult patients may be given a combination of slippery elm water and barley to drink, at least a pint per day.

    Traditional Chinese medicine

    To treat dysentery, traditional Chinese doctors use astringent drugs, which are intended to constrict or tighten mucous membranes and other body tissues to slow down fluid loss. Myrobalan fruit (Terminalia chebula), nut galls (swellings produced on the leaves and stems of oak trees by the secretions of certain insects), and opium extracted from the opium poppy (Papaver somniferum) are the natural materials most commonly used. Paregoric, a water-based solution of morphine that is still used in the West to treat diarrhea, is derived from the opium poppy.

    Other plant-based remedies

    Researchers in Mexico reported in early 2005 that the roots of Geranium mexicanum, a plant that produces a sap traditionally used to treat coughs or diarrhea, contains compounds that are active against both Giardia lamblia and Entamoeba histolytica. Plant biologists in Africa are studying the effectiveness of African mistletoe (Tapinanthus dodoneifolius), a traditional remedy for dysentery among the Hausa and Fulani tribes of Nigeria.

    Dietary supplements

    A study published in the American Journal of Clinical Nutrition in early 2005 reported that supplemental zinc (twice the recommended daily dietary allowance) boosts the body’s immune response during acute shigellosis.


    There are at least ten different homeopathic remedies used to treat diarrhea. Contemporary homeopaths, however, distinguish between diarrhea that can be safely treated at home with such homeopathic remedies as Podophyllum, Veratrum album, Bryonia, and Arsenicum, and diarrhea that indicates dysentery and should be referred to a physician. Signs of dehydration (loss of normal skin texture, dry mouth, sunken eyes), severe abdominal pain, blood in the stool, and unrelieved vomiting are all indications that mainstream medical care is required.


    Most adults in developed countries recover completely from an episode of dysentery. Children are at greater risk of becoming dehydrated, however; bacillary dysentery in particular can lead to a child’s death from dehydration in as little as 12–24 hours.

    • Bacillary dysentery. Most patients recover completely from shigellosis, although their bowel habits may not become completely normal for several months. About 3 percent of people infected by S. flexneri will develop Reiter’s syndrome, which may lead to a chronic form of arthritis that is difficult to treat. Elderly patients or those with weakened immune systems sometimes develop secondary bacterial infections after an episode of shigellosis.
    • Amebic dysentery. Most people in North America who become infected with E. histolytica do not become severely ill. Patients who develop a severe case of amebic dysentery, however, are at increased risk for such complications as fulminant colitis or liver abscess. About 0.5 percent of patients with amebic dysentery develop fulminant colitis, but almost half of these patients die. Between 2 and 7 percent of cases of amebic liver abscess result in rupture of the abscess with a high mortality rate. Men are 7–12 times more likely to develop a liver abscess than women. Any patient diagnosed with amebic dysentery should have stool samples examined for relapse 1, 3, and 6 months after treatment with medications whether or not they have developed complications.
    • Dysentery caused by other protozoa. Cryptosporidiosis may lead to respiratory infections or pancreatitis in patients with AIDS. The risk of these complications, however, is reduced in AIDS patients who are receiving highly active antiretroviral therapy (HAART).
    • Viral dysentery. Most people in North America recover completely without complications unless they become severely dehydrated. Viral dysentery in children in developing countries, however, is a major cause of mortality.
    • Dysentery caused by parasitic worms. Untreated whipworm infections can lead to loss of appetite, chronic diarrhea, and retarded growth in children. Untreated schistosomiasis can develop into a chronic intestinal disorder in which fibrous tissue, small growths, or strictures (abnormal narrowing) may form inside the intestine. Patients treated for schistosomiasis should have stool samples checked for the presence of worm eggs 3 and 6 months after the end of treatment.


    The disease agents that cause dysentery do not confer immunity against reinfection at a later date. As of 2005 there are no vaccines for bacillary dysentery or amebic dysentery; however, a vaccine against schistosomiasis is under investigation. An oral vaccine against rotavirus infections was developed for small children but was withdrawn in 2004 because it was associated with an increased risk of small-bowel disorders. Newer vaccines against rotaviruses and caliciviruses are being developed as of 2005.

    Public health measures

    Public health measures to control the spread of dysentery include the following:

    • Requiring doctors to report cases of disease caused by Shigella, Entamoeba histolytica, and other parasites that cause dysentery. Careful reporting allows the CDC and state public health agencies to investigate local outbreaks and plan prevention efforts.
    • Posting advisories for travelers about outbreaks of dysentery and other health risks in foreign countries. The Travelers’ Health section of the CDC website ( is a good source of up-to-date information.
    • Instructing restaurant workers and other food handlers about proper methods of hand washing, food storage, and food preparation.
    • Instructing workers in day care centers and nursing homes about the proper methods for changing and cleaning soiled diapers or bedding.
    • Inspecting wells, other sources of drinking water, and swimming pools for evidence of fecal contamination.

    Personal precautions

    Individuals can lower their risk of contracting dysentery by the following measures:

    • Not allowing anyone in the household who has been diagnosed with amebic or bacillary dysentery to prepare food or pour water for others until their doctor confirms that they are no longer carrying the disease agent.
    • Avoiding anal sex or oral-genital contacts.
    • Washing the hands carefully with soap and water after using the bathroom, and supervising the handwashing of children in day care centers or those at home who are not completely toilet-trained.
    • When traveling, drinking only boiled or treated water, and eating only cooked hot foods or fruits that can be peeled by the traveler.
    • Avoiding swimming in fresh water in areas known to have outbreaks of schistosomiasis.

    Source: The Gale Group. Gale Encyclopedia of Medicine, 3rd ed.

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