Shigellosis

What is shigellosis?

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.

Shigellosis is more common among children ages 1 to 4. Children of this age have a higher rate of infection 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 of shigellosis

Although health experts don't know why, some people do not become ill despite Shigella infection. Others develop only a brief fever, or a brief fever with or without mild diarrhea that goes away on its own. However, about 25% of patients 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.

Rarely, Shigella bacteria can affect other parts of the body far from the digestive tract. When this happens, there may be a rash, joint pain, confusion, and/or kidney failure.

Diagnosing shigellosis

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 of shigellosis

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.

Preventing shigellosis

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 water that has been treated or boiled. Eat foods that have been cooked thoroughly. Don't eat unpeeled fruits. Peel fruits yourself immediately before eating them.

Treating shigellosis

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

If Shigella infection causes significant symptoms, your doctor will recommend treatment with fluids and an antibiotic such as levofloxacin or ciprofloxacin, although other antibiotics (such as azithromycin and trimethoprim-sulfamethoxazole) may also be effective.

Many strains of Shigella have developed resistance to multiple antibiotics, especially among men who have sex with men and people infected with HIV or experiencing homelessness. Your doctor will choose an antibiotic based on the chances of your having a resistant strain; treatment may change based on test results or if the illness is not improving.

The use of antidiarrheal medicines to slow bowel movements is not recommended, because such treatment can increase the time it takes to clear the bacteria from the lower intestine and make the infection worse.

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.

Prognosis

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

Additional info

Centers for Disease Control and Prevention (CDC)
https://www.cdc.gov/