SHIGELLOSIS IS an infectious diarrheal disease caused by Shigella bacteria, aerobic Gram-negative rods that find comfortable reservoirs in the human colon. According to the CDC, over 7,000 lab-confirmed cases, or 4.82 cases per 100,000 population, are reported yearly within the United States, making it the third most common cause of bacterial infectious diarrheal illness (behind Salmonella and Campylobacter).1Shigella bacteria are present in the stool of infected persons while they have diarrhea and for up to 2 weeks afterward. Shigella is very contagious; exposure to even a tiny amount of contaminated fecal matter (just 10 to 200 organisms) can cause infection.2
Among the four species of Shigella, Shigella sonnei (S. sonnei) and Shigella flexneri (S. flexneri) are the most common in the United States. Shigella boydii (S. boydii) and Shigella dysenteriae (S. dysenteriae) are rarely found in the United States but are important causes of disease in less developed countries.3 According to the CDC, each year approximately 80 to 165 million cases of Shigella disease occur worldwide and result in an estimated 600,000 deaths annually.
Within each species of Shigella, there are one or more serotypes. S. dysenteriae type 1 is particularly associated with deadly epidemics, and is common during times of civil unrest and refugee migration. One such outbreak occurred in June 2004 in a displaced persons camp in Darfur; the World Health Organization reported 1,340 cases of S. dysenteriae with 11 deaths.4 Another confirmed outbreak in 2003 in the Central African Republic involved 379 cases and 23 deaths. Civil war in the region and population migration to neighboring regions hindered control efforts; ease of transmission and rapid development of antimicrobial resistance were other obstacles to ending the outbreak.4
Shigellosis is spread by oral ingestion of the bacteria, primarily in fecally contaminated food or water, or by contaminated hands preparing or handling food. Hands can become contaminated from caring for an infected person while handling waste or diapers, or by handling contaminated objects such as toys in a childcare setting. Produce can be contaminated with Shigella if the growing fields contain human sewage. Flies can spread contamination if they breed in infected feces then land on food. Swimming in a contaminated river or pond water can also lead to illness, as can oral exposure to tiny amounts of fecal material during sexual contact.2
Patients at increased risk for developing shigellosis and complications from shigellosis include young children, those who travel to developing countries, and men who have sex with men. Large outbreaks have also occurred in traditionally observant Jewish communities. Patients with HIV can experience prolonged illness and bacteremia.5
Signs and symptoms
A day or two after ingesting the bacteria, patients infected with Shigella develop diarrhea (sometimes bloody and mucoid) and may also develop fever, abdominal pain, and cramping. Dehydration may be present, and seizures in children may occur in severe cases.2,6
Shigellosis usually lasts 5 to 7 days in persons with intact immune systems, although it may be several months before bowel habits return to normal.2 Some patients may have mild symptoms; however, they can still transmit the Shigella bacteria to others unless they implement careful preventive measures such as handwashing (especially after toileting and changing or handling diapers).2,4,6,7
Diagnostic testing involves culturing feces or a rectal swab. Shigella bacteria deteriorate quickly outside the body, so specimens for culture must be immediately transported to the lab and processed rapidly.8 Because septicemia is a possible complication, specimens for blood culture should also be obtained from severely ill and immunocompromised patients.7
Rest and hydration may be all that many patients need. Avoid medications that slow intestinal motility, such as loperamide hydrochloride or diphenoxylate hydrochloride-atropine sulfate, because they may prolong symptoms.4,7
Antibiotics aren't indicated in most cases, although they can reduce the duration of symptoms for severe cases. However, Shigella organisms rapidly develop resistance to antibiotics. Although commonly prescribed antibiotics (such as ciprofloxacin and azithromycin) may be effective in treating shigellosis, the choice of antibiotic must be guided by sensitivity and resistance patterns in patient and community specimens.4,7-9
Mortality for shigellosis ranges from 1% to 20%; s. dysenteriae is the most lethal strain. Outcomes depend on a patient's underlying health, complications, and the availability of medical care.8 Most shigellosis infections are self-limiting; however, complications that may develop, especially in cases of S. dysenteriae, include the following.
- Bloodstream infections:Shigella organisms in the gut can migrate into the bloodstream if the intestinal lining is damaged. This secondary infection is most common among patients with weakened or undeveloped immune systems, such as neonates, and those with chronic conditions such as HIV, cancer, or severe malnutrition.7
- Seizures: Although not well understood, generalized seizures have been reported among children and adolescents younger than age 15 with shigellosis, usually resolving without long-term treatment. Children who experience seizures while infected with Shigella typically have a high fever and/or electrolyte imbalances.7,8
- Hemolytic-uremic syndrome (HUS): HUS is characterized by thrombocytopenia, microangiopathic hemolytic anemia, and acute kidney injury and may require dialysis. This complication can occur when Shiga toxin is produced in the colon by S. dysenteriae type 1 and is often accompanied by bloody diarrhea.6,7
- Arthritis: About 2% of patients infected with S. flexneri later develop pain in their joints, or postinfectious arthritis, known as Reiter syndrome. This reactive arthritis may be accompanied by conjunctivitis and urethritis and can develop weeks or months after shigellosis.2,7
- Intestinal perforation and toxic megacolon: Toxic megacolon is a life-threatening condition that occurs when infection causes rapid dilation of the colon, leading to intestinal perforation requiring immediate surgical repair. These have been reported as a rare complication of Shigella.4,8
Nursing care is mainly supportive. The patient will need rehydration and electrolyte replacement as prescribed. Monitor fluid intake and output, vital signs, and bowel sounds, which may be hyperactive or hypoactive. Assess for signs of dehydration, including poor skin turgor, lack of tears in infants, and orthostatic hypotension. Initiate seizure precautions in children and adolescents. Monitor amount and characteristics of bowel movements and examine stool for blood and mucus. Observe for adverse reactions to antibiotics, if prescribed.
Maintain standard precautions against transmission, with contact precautions for diapered or incontinent patients. Teach patients and families about hand hygiene and disinfection; everyone in contact with the patient must practice meticulous hand hygiene and glove use, particularly after toileting and/or diaper care.10 It's important to disinfect supplies and surfaces in the patient's physical environment. Teach the patient and his or her family that appropriate prevention and hygiene measures will help prevent reoccurrence.
Confirmed Shigella infection is reportable to your local health department, which in turn reports to the state and investigates contacts for additional cases; states voluntarily report Shigella outbreaks to the CDC. To assist in investigative and control efforts after the fact, take a comprehensive travel and food history. People with shigellosis shouldn't work in food service or child care, so include where your patient works when taking the history.8 Consult your facility infection prevention staff and public health liaison for assistance.
6. World Health Organization. Guidelines for the control of shigellosis, including epidemics due to Shigella dysenteriae
type 1. Geneva, Switzerland: World Health Organization; 2005.
7. American Academy of Pediatrics. Red Book 29th edition: report of the committee on infectious diseases. Elk Grove Village, IL: American Academy of Pediatrics; 2012.
8. Heymann DL. Control of Communicable Diseases Manual
. 20th ed. Washington, DC: American Public Health Association; 2015.
10. Lippincott, Williams, & Wilkins. Lippincott's Guide to Infectious Diseases
. Ambler, PA: Wolters Kluwer; 2011.