Shigellosis

Shigellosis (pronounced: shih-guh- lo -sus) is an intestinal infection caused by Shigella (pronounced: shih- geh -luh) bacteria. Shigellosis, which is also called bacillary dysentery, is an acute intestinal infection that causes a high fever (especially in children) and acute, self-limiting diarrhea with tenesmus; it also may cause electrolyte imbalance and dehydration. There are about 140 million cases of shigellosis worldwide, with almost 600,000 deaths, particularly in children under age 5, especially in underdeveloped countries.

Shigellosis commonly occurs in low-income, minority-group residents. Rates are especially high in children who attend day-care centers, retarded children in custodial care, and in people from poor, urban communities.

The prognosis for this infection is good. Mild infections normally subside within 10 days; severe infections may persist for 2 to 6 weeks.

Causes

Shigellosis is caused by Shigella, a short, nonmotile, gram-negative, rod-shaped bacterium. Shigella can be classified into four groups, all of which may cause shigellosis: group A, consisting of S. dysenteriae, which is most common in Central America and causes particularly severe infection and septicemia; group B, consisting of S.flexneri: group C, consisting of S. boydii: and group D, consisting of S. sonnei, which accounts for most cases reported in the United States.

Transmission is through the fecal-oral route, by direct contact with contaminated objects, or through ingestion of contaminated food or water. The housefly may be a vector.

Signs and symptoms

Individuals infected with Shigella may experience abdominal cramping, fever and mild or severe diarrhea, often with fever and traces of blood or mucous in the stool. Some infected people may not show any symptoms.

Diagnostic tests

During acute illness, stool cultures usually are positive. Microscopic examination of a fresh stool specimen may reveal mucus, red blood cells, and polymorphonuclear leukocytes; direct immunofluorescence with specific antisera may reveal Shigella. Severe infection increases hemagglutinating antibody levels. Sigmoidoscopy may reveal typical superficial ulcerations.

Treatment

Shigellosis treatment involves contact precautions and includes nutritional support to reverse catabolism and, most important, replacement of fluids and electrolytes with I.V infusions in sufficient quantities to maintain a urine output of 40 to 50 ml/hour and correct imbalances.

Antibiotics are of questionable value but may be used in an attempt to eliminate the pathogen and thereby prevent further spread. Ampicillin or trimetho­prim-sulfamethoxazole is generally recommended and may be useful in severe cases, especially in children with overwhelming fluid and electrolyte losses.

Prevention

Shigellosis is an extremely contagious disease; good hand washing techniques and proper precautions in food handling will help in avoiding spread of infection. Children in day care centers need to be reminded about hand washing during an outbreak to minimize spread. Shigellosis in schools or day care settings almost always disappears when holiday breaks occur, which sever the chain of transmission.