Shigellosis
Shigellosis is infection with species of the gram-negative bacillus Shigella, which results in dysentery that is characterized by frequent watery stools, often with mucus and blood, pain, fever, and dehydration.
Shigella is a major cause of dysentery throughout the world and is responsible for 5 to 10% of diarrheal illnesses in many areas. About half a million people in the United States develop shigellosis every year. The bacteria appear in the stool of infected people and are usually spread by person-to-person contact. Sometimes, contaminated food serves as a common source of infection. Epidemics are most frequent in overcrowded populations with inadequate sanitation. High-risk sites include child-care centers, long-term care facilities, and military camps. Children are especially likely to become infected and usually develop more severe symptoms.
The bacteria cause disease by penetrating the lining of the intestine--primarily, the large intestine--resulting in swelling and sometimes shallow sores.
Symptoms
The first symptoms are abdominal pain and watery diarrhea that start 1 to 4 days after infection. Fever is frequently present and may reach 106° F. Vomiting is not common but may occur. After 1 or 2 days, many people have pain on passing stool, which contains blood and mucus. The number of bowel movements generally increases rapidly, possibly exceeding 20 per day. Weight loss and dehydration become severe. Severe dehydration that leads to shock and death occurs mainly in chronically ill adults and children younger than 2 years of age.
Some children develop seizures. It is not known if these seizures occur simply from the high fever or as a specific complication of shigellosis. Some adults develop eye inflammation and reactive arthritis (Reiter's syndrome (see Section 5, Chapter 67)). Rarely, intestinal perforation occurs. Severe straining during bowel movements may cause part of the rectum to be pushed out of the body (rectal prolapse). Permanent loss of bowel control can result.
Diagnosis and Treatment
A doctor suspects shigellosis from the typical symptoms of pain, fever, and bloody diarrhea in a person who lives in an area where Shigella is common. The diagnosis is confirmed by culturing freshly passed stool.
Treatment consists mainly of replacing fluids and salts lost because of diarrhea. Oral replacement is satisfactory for most people, but some may need to receive fluids intravenously. In most cases, the disease resolves within 4 to 8 days without antibiotics. Severe infections may last 3 to 6 weeks. Antibiotics such as trimethoprim-sulfamethoxazole, norfloxacin, ciprofloxacin, or furazolidone may be given when the person is very young or very old, when the disease is severe, or when there is a high risk of the infection spreading to other people. The severity of the symptoms and the length of time the stool contains Shigella are reduced with antibiotics. Antidiarrheal drugs (such as diphenoxylate or loperamide) may prolong the infection and should not be used.
| 
