A close cousin to E. coli, Shigella is a Shiga toxin-producing bacteria that nests in the colon, releasing toxins and causing inflammation. The released toxins cause death of colon cells. With fewer than 100 Shigella cells needed to cause a full-blown infection, Shigella is a dangerous, and sometimes deadly, bacterium.
How Common is Shigella?
The CDC estimates that 500,000 total cases of shigellosis occur in the United States every year. Shigellosis is also characterized by seasonality, with the largest percentage of reported cases occurring between July and October, and the smallest proportion occurring in January, February, and March. Sporadic (or non-outbreak) infections account for the majority of cases and, in general, the exact means by which persons are infected (risk factors) are not yet well documented or understood.”
Shigella is the leading cause of diarrheal illness in the world, with 80 to 165 million cases per year ¾and results in about 700,000 deaths a year worldwide.
What is Shigella?
Shigella is a bacterium that causes the foodborne illness known as shigellosis. Shigella is classified into four distinct categories: Shigella sonnei, Shigella flexneri, Shigella boydi, and Shigella dysentenae. The most common type of Shigella in the United States is Shigella sonnei.
What Are the Sources of Shigella?
Shigella can be traced to contaminated food or water, or contact with an infected person. This type of contact would involve the transmission of feces or fecal matter from one person to the mouth of another. Additionally, it only takes a very small amount of fecal matter to contaminate the host and cause symptoms. Foods that are most commonly associated with this pathogen are salads and sandwiches that are handled a great deal in their preparation, and raw vegetables contaminated in the field. Additionally, the bacterium Shigella can proliferate on unclean utensils, plates, and cups. Shigella is also known to be found in developing countries without proper drinking water treatment facilities.
What are the Symptoms of Shigella Infection?
The most common symptoms of Shigella present with diarrhea, fever, and stomach cramps, with onset of symptoms 12 to 96 hours after exposure. Diarrhea can contain mucus and also blood, and sometimes an individual can experience rectal spasms.
Most Shigella infections do not lead to hospitalization. Even so, the CDC estimates that over 50,000 Americans are hospitalized each year with severe food poisoning symptoms caused by Shigella. Older people and people who are immune-compromised have the highest risk of experiencing severe complications.
It is important to note that early medical attention in severe cases can greatly reduce the risk of developing long-term complications, such as hemolytic uremic syndrome, reactive arthritis, and others.
Do Shigella Infections Have Long-Term Complications?
Shigella infections can sometimes cause further and more far-reaching complications. About 2% of infected individuals can later develop pain in their joints, irritation of the eyes, and painful urination. Post-infectious arthritis is caused by a reaction to Shigella bacteria occurs only in people that are genetically predisposed to it. Some patients can develop digestive disorders such as irritable bowel syndrome.
Shigella infections can also cause complications with the central nervous system. In some cases, children infected with Shigella can develop seizures. The death of blood cells could lead to ongoing issues with flood flow to the brain and spinal cord. In rare cases, strokes may also occur.
However, the most concerning complication of Shigella infections is the potential to develop Hemolytic Uremic Syndrome. Children and adolescents are those that are most commonly susceptible to developing HUS.
This potentially fatal disorder begins with the toxin released by the bacteria destroying the red blood cells in an infected person’s body. Once the dead blood cells reach the kidneys, they clog the filter system of the kidneys, causing blockage. Without adequate filtration, the body is unable to cleanse itself. This issue could lead to kidney failure, and even death.
The symptoms of hemolytic uremic syndrome, or HUS, are concerning and usually show within 5-10 days of Shiga toxin infections. Some of these symptoms include:
- Easy bruising
- Dark urine
- Decreased urine output
- Pale skin
Early medical care provided in severe cases can reduce the likelihood of developing long-term complications.
Why is Shigella a Concern for Daycares?
Young children and toddlers are among those most likely to contract Shigella. In fact, the illness is most commonly seen in child-care settings and schools. This makes it concerning as it spreads quickly.
It is also very difficult to prevent the transmission of Shigella in daycare settings because, overall, it is hard to prevent the spread of almost any kind of bacteria within such settings. A child who sheds the bacteria in their stool can be symptom-free and show no signs of the infection. However, anyone who is infected with the Shigella bacteria can suffer varying degrees of diarrhea as well as other complications. A Shigella infection can even cause death in some cases, especially in those who are immune compromised.
How Are Shigella Infections Treated?
Shigella infections are typically treated with supportive care¾regular rest and lots of fluids. However, as Shigella releases a toxin that could cause long-term issues, immediate medical attention is recommended if any stools are bloody or if the infection worsens.
How Do You Prevent Shigella Infections?
Shigella infections are one of the most virulent of the foodborne illnesses. As with many pathogens, no vaccine is currently available, but the procedures mentioned above can be of help in preventing the transmission of the illness.
Until that occurs, prevention is key. Chlorination is another important factor in decreasing the incidence of all enteric bacterial infections. The spread of Shigella from one infected person to another can be prevented most efficiently by frequent and thorough hand washing with soap and hot water, especially when it comes to young children. Additionally, if an infant or child becomes infected with Shigella, the child’s diapers should be properly disposed in a closed-lid garbage can, and person(s) who change the diapers should wash their hands immediately. The area should be sanitized with a disinfectant such as diluted bleach.
Food safety precautions go a great distance in helping to prevent Shigella bacteria from contaminating food and water, including being meticulous when preparing food. Always ensure that food preparation surfaces are clean, wash hands thoroughly before and after preparing the food, and separate meat from raw vegetables. People who have already contracted shigellosis should never prepare food or drinks until it has been medically confirmed that they are no longer shedding the bacteria in their stool. Additionally, daycare centers should not provide water play areas, and at beaches, handwashing areas should be provided near the swimming area. When traveling to under-developed countries, drink only treated or boiled water and eat only hot, cooked foods.
Is There a Shigella Vaccine?
Not yet, but they are working on one. A vaccine to prevent Shigella is not yet available, but several candidate vaccines have shown promise
What Are the Economic Concerns with Shigella?
Productivity loss is an economic result of Shigella infections. Combined with medical costs, it is estimated that close to one billion dollars is lost each year. A study published in 2010 noted that treatment of a Shigella infection (with a hospital stay) was approximately $7,092, with 1,227 deaths per year, and a total cost to United States residents of $686 million.