Shigellosis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at May 29, 2016
StartDiseasesShigellosis

Shigellosis is a type of gastrointestinal infection caused by the Shigella bacteria. The condition affects approximately 500,000 people in the United States each year with the majority of cases occurring in children between the ages of 2 and 4 and their caregivers. Most cases of Shigella infection resolve on their own within a week or with treatment with antibiotics

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Definition & Facts

Shigella refers to a family of bacteria discovered by a Japanese scientist named Shiga over a century ago. Shigella sonnei is responsible for over two-thirds of the shigellosis cases in the United States. Shigella flexneri bacteria cause the majority of the remaining cases. The incidence of Shigella infection is slightly higher during the summer due to the increased use of public pools and swimming areas.

Shigella boydii and Shigella dysenteriae infections are rare in the U.S. and are most often seen in the developing world. Shigella dysenteriae is especially dangerous and can cause deadly epidemics. Those most at risk for contracting shigellosis or experiencing complications include:

  • Young children and their family members and caregivers.
  • Individuals who engage in anal sex or oral sex
  • Individuals who live or travel in areas with inadequate sanitation.
  • People living in group housing or other close quarters.
  • Individuals who swim in public areas.
  • Individuals with weakened immune systems.

Symptoms & Complaints

The symptoms of shigellosis typically develop one to two days after exposure to the bacteria. The Shigella bacteria is extremely contagious, so even a small amount can cause illness. The most common symptom is diarrhea that may contain blood or mucus. This is usually accompanied by abdominal pain or cramps and a fever.

It is possible to be asymptomatic and still transmit the infection to others. The bacteria can remain in the stool for up to two weeks after the diarrhea has resolved, and bowel habits may not be completely normal for several months following infection. Although most people recover from shigellosis uneventfully, the infection can cause complications, including:

Causes

A Shigella infection occurs as the result of fecal/oral transmission of the bacteria. This usually occurs due to poor hand washing practices or by eating contaminated food. Shigellosis is most prevalent in areas that are crowded or where access to sanitation may be limited, such as nursing homes, daycare centers, or refugee camps. The condition is extremely common among children who are not fully toilet trained and is easily spread through contact with dirty diapers or other contaminated objects, such as toys, changing tables, and bathroom fixtures.

The bacteria can also be spread through food that is harvested from a field containing sewage or that is handled by an infected individual. Food can also become contaminated by flies that have bred in contaminated feces. Water can become contaminated if an infected person swims in it or by sewage runoff.

It is also possible to transmit the bacteria sexually through anal or oral sex that may provide direct or indirect contact with fecal matter. Once a person is infected with Shigella, they are unlikely to be infected with that same strain for several years; however, they can still become infected with another type of Shigella bacteria. 

Diagnosis & Tests

A doctor may suspect a Shigella infection based on physical symptoms, as well as the patient’s diet, work, and home environments. The fever and bloody diarrhea associated with shigellosis are also symptoms of a number of different diseases, so lab tests are the most accurate method of confirming a Shigella infection. This is typically done through a stool culture and antibiotic sensitivity test to verify the presence of Shigella bacteria and to determine which antibiotics may be most effective. Blood tests may also be used to rule out other conditions or if the symptoms are particularly severe. 

Treatment & Therapy

If an individual is in otherwise good health and their symptoms are mild, it is usually best to let the infection run its course. While antibiotics may shorten the duration of the infection, Shigella bacteria have become increasingly drug-resistant in recent years. Health officials recommend only using antibiotics if symptoms are especially severe. The antibiotics most often used for shigellosis include ampicillin, trimethoprim/sulfamethoxazole, ceftriaxone, and ciprofloxacin.

Antibiotic therapy is most appropriate for infants, the elderly, people with weakened immune systems, and in environments where there is a high risk of transmission. Individuals with shigellosis should avoid anti-diarrheal medications like loperamide or atropine since they can exacerbate symptoms.

It is important to prevent dehydration by drinking at least a cup of water or rehydration drink after each bowel movement. Water, sports drinks, or Pedialyte® are the best choices for replacing vital fluids and electrolytes. Fruit juices and sodas should be avoided since they contain too much sugar and do not provide the necessary electrolytes.

It is best to eat a diet that allows the stomach to recover; spicy foods, coffee, and alcohol should be avoided until all the symptoms have resolved. Hospitalization and intravenous rehydration may be required if dehydration becomes severe. 

Prevention & Prophylaxis

There are no vaccines available to prevent shigellosis. The best method of prevention is frequent and careful hand washing. Young children should be encouraged to wash their hands often under adult supervision.

Anyone who changes the diaper of a child with shigellosis should dispose of the diaper in a sealed garbage can, wash their hands thoroughly, and wash the child’s hands. All changing areas should be disinfected with a bleach solution or antibacterial wipes. If possible, children with a Shigella infection should be kept away from other children until they are symptom-free.

Individuals with an infection should not prepare food or drinks for others until they have been symptom-free for at least two days. It is best to avoid swimming in or drinking water from untreated ponds, lakes, or pools.

Daycare providers are also advised against providing water play areas for children due to the high risk of contamination. Travelers should exercise extra caution when traveling in less developed countries. This includes only drinking boiled water and only eating cooked foods or foods that can be peeled.