Shigella Food Poisoning
Shigellosis is a foodborne illness caused by a group of bacteria called Shigella. The illness is most typically characterized by diarrhea (often bloody), fever, and stomach cramps, beginning a day or two after eating food contaminated by Shigella.
According to the U.S. Centers for Disease and Prevention (CDC), about 18,000 cases of shigellosis are reported in the United States each year. Because many milder cases are not diagnosed or reported, the actual number of infections may be twenty times greater.
What are the symptoms of Shigella foodborne illness?
Symptoms of Shigella foodborne illness may include diarrhea (often bloody), fever, abdominal pain, cramps, tenesmus (straining to have bowel movements), and malaise. Symptoms may appear a day or two after consuming contaminated food. Shigellosis usually resolves in 5-7 days.
The elderly and young children may be more likely to develop severe diarrhea, eventually requiring hospitalization.
About 3% of individuals who are infected with a type of Shigella known as Shigella flexneri will develop a condition called Reiter’s Syndrome, or “reactive arthritis.” Reiter’s Syndrome is characterized by joint pain, eye irritation (conjunctivitis), and painful urination. Most people with Reiter’s Syndrome will recover within a year; however, this syndrome can lead to chronic arthritis.
How are Shigella infections caused?
Shigella is transmitted from person to person via fecal to oral contact. In the case of Shigella foodborne illness, contaminated food, which may look, smell, and taste normal, is consumed. Food can become contaminated by:
- food handlers who do not adequately wash their hands with soap after using the bathroom;
- harvesting vegetables from sewage contaminated fields;
- flies, which breed in infected feces and then contaminate food;
- drinking or swimming in contaminated water. Water may become contaminated if sewage runs into it, or if someone with shigellosis swims in it.
Because so few organisms are needed to cause infection, Shigella food poisoning can spread rapidly in daycare centers, nursing homes, and in any other setting where hygiene (particularly hand washing habits) is poor. Infected toddlers, not yet fully toilet-trained, can spread the illness to family members and playmates. Children aged 2-4 are the most likely to get shigellosis.
Shigella may be found in a person’s stool weeks after symptoms have resolved. Some individuals who are infected may have no symptoms at all, yet they may still pass the bacteria to others.
How is Shigella infection diagnosed and treated?
According to the CDC, infection with Shigella is diagnosed through laboratory testing that can detect the bacterium in the stool of an infected person. These tests are sometimes not performed unless the laboratory is instructed specifically to look for the organism. (It is important to discuss with your physician which laboratory tests are being run.) The laboratory can also do special tests to tell which type of Shigella the person has and which antibiotics, if any, would be best to treat the infection.
The CDC also reports that shigellosis can usually be treated with antibiotics. The antibiotics commonly used for treatment are ampicillin, trimethoprim/sulfamethoxazole (also known as Bactrim* or Septra*), nalidixic acid, or ciprofloxacin. Appropriate treatment kills the Shigella bacteria that might be present in the patient’s stools and shortens the illness. Because Shigella is increasingly becoming resistant to antibiotics, and most people with mild infections will usually recover quickly without antibiotic treatment, when many individuals in a community are affected by shigellosis, antibiotics are sometimes used selectively to treat only the more severe cases. Antidiarrheal agents, such as loperamide (Imodium*) or diphenoxylate with atropine (Lomotil*), are likely to make the illness worse and should be avoided
Are there complications with Shigella infections?
Complications due to Shigella infection may include severe dehydration, systemic infection (bacteria entering the blood stream), and seizures due to high fever in children under the age of 2. In some people, especially young children and the elderly, diarrhea can be so severe that the patient requires hospitalization. While symptoms usually resolve within 7 days, it may be months before bowel habits return to normal.
A small number of individuals (3%) who are infected with Shigella flexneri will go on to develop Reiter’s Syndrome, also referred to as “reactive arthritis.” This syndrome is characterized by joint pain, irritation of the eyes (conjunctivitis), and painful urination. It usually resolves within a year; however, it can lead to chronic arthritis.
How can Shigella infection be prevented?
The following precautions can help prevent the spread of Shigella from an infected individual:
- Frequent and careful hand washing with soap and water.
- Frequent and supervised hand washing for all children in daycare centers and at home.
- Young children and toddlers with Shigella infection should be kept from contact with uninfected children
- People who have shigellosis should not prepare food or pour water for others until it has been determined that they no longer carry the Shigella bacterium.
- Individuals changing the diaper of a child with shigellosis should immediately wash their hands with soap and water, dispose of the diaper in a closed-lid garbage can, and wipe down changing area with an appropriate disinfectant.
- Avoid direct or even indirect contact between reptiles (turtles, iguanas, other lizards, snakes) and infants or immunocompromised individuals.
- Basic food safety precautions and regular drinking water treatment prevent shigellosis. At swimming beaches and public pools, having enough bathrooms near the swimming area helps keep water from becoming contaminated.
- While traveling in developing countries, drink only treated or boiled water, and do not use ice in beverages. Eat only cooked hot foods or fruits that you peel yourself.