Shigellosis

What Is It?

Shigellosis is an infection of the colon (large intestine) caused by Shigella bacteria. Shigellosis is also called bacillary dysentery because it can cause severe diarrhea. However, the infection often causes only mild symptoms.

Shigella can be found in water polluted with infected sewage. Bacteria commonly enter the body through a contaminated drinking supply. Shigella bacteria also can be found on food that has been rinsed with unclean water, grown in fields contaminated with sewage, or touched by flies that have touched feces. Shigella bacteria can reach the mouth on dirty fingers that have touched items soiled with feces, including dirty diapers, toilets and bathroom fixtures. Outbreaks of shigellosis are most common in areas where sanitation is poor, and in places where people live under confined or crowded conditions. Shigella also can be passed from person to person during anal-oral sex.

Worldwide, an estimated 140 million people develop shigellosis each year, and about 600,000 die. Most of these deaths occur in developing countries among children under age 5. In the United States, only 20,000 cases are reported each year, but the actual number of infections is probably more than 200,000 per year. Shigellosis is more common among children ages 1 to 4. Children of this age are especially at risk because they are starting to use the toilet and often forget to wash their hands. Infants are at the highest risk of becoming seriously ill from a Shigella infection.

Symptoms

Although health experts don't know why, some people take in Shigella bacteria without becoming ill. Others develop only a brief fever, or a brief fever with mild diarrhea that goes away on its own. About 25% of patients, however, develop high fever, abdominal cramping and severe diarrhea that can contain blood, mucus and pus. These people can have 10 to 30 bowel movements each day, along with a persistent urge to have a bowel movement that can lead to rectal prolapse (an abnormal protrusion of the rectum). Rarely, Shigella bacteria can affect other parts of the body far from the digestive tract. When this happens, there can be seizures, confusion or coma, kidney failure, arthritis, rashes or other symptoms.

Diagnosis

Your doctor will ask about your symptoms and about the appearance of your bowel movements. He or she will ask if you have recently traveled to developing countries, been in contact with people who have severe diarrhea, or might have been exposed to contaminated pools, lakes or food.

Your doctor will diagnose shigellosis based on a physical examination and the results of laboratory tests. These tests include taking a swab of your rectum or a sample of your stool (feces). If you have signs of dehydration (excessive loss of body water) or significant blood loss, additional blood tests may be necessary.

Expected Duration

In most otherwise healthy people with mild shigellosis, diarrhea goes away on its own within five to seven days. However, in very young children, the elderly or people with chronic illnesses, shigellosis can be severe and can lead to life-threatening dehydration and other complications within a few days.

Prevention

There is no vaccine to protect against shigellosis. To prevent the spread of Shigella bacteria, you should:

• Practice good hygiene, especially frequent handwashing.
• Wash your hands immediately after changing a child's diaper, especially if the child has diarrhea.
• Dispose of soiled diapers in closed-lid garbage cans.
• Swim only in lakes and pools whose water quality is monitored by local health officials.
• When traveling to developing countries, drink only water that has beeb treated or boiled eat only foods that have been cooked thoroughly. Never eat unpeeled fruits, and always peel fruits yourself immediately before eating them.

Treatment

If you have a mild case of shigellosis, you probably won't need treatment because your symptoms will probably go away on their own. Sometimes, doctors may prescribe antibiotics if there are very young or very old members in a household who could get the infection.

If you have a severe case of shigellosis, your doctor will prescribe fluids to treat dehydration and an antibiotic based on how you became infected. For example, if you became infected with shigellosis in the United States, your infection probably will respond to common antibiotics such as ampicillin (Polycillin, Totacillin, Omnipen), trimethoprim-sulfamethoxazole (Bactrim, Septra and other brand names), tetracycline (sold under many brand names), or ciprofloxacin (Cipro). However, if you became infected during travel to a developing country, the infecting strain of Shigella is more likely to be resistant to these common antibiotics, and you may need a newer or less common antibiotic.

The use of antidiarrheal medicines to slow bowel movements is controversial. It can take longer to clear the bacteria from the lower intestine and the illness caused byt he infection could become more severe.

When To Call A Professional

Call your doctor if you develop severe diarrhea, especially if the bowel movements contain blood or mucus. Call your doctor whenever you have a fever and severe diarrhea. Seek immediate attention if you have signs of dehydration, such as very dry mouth and lips, and lightheadedness when you stand, whether or not you are thirsty.

Prognosis

In developed countries, most people with shigellosis recover completely. In underdeveloped countries, the risk of complications, including death, is signifcantly higher.