Symptoms of Shigella Infection
Most people who are infected with Shigella develop diarrhea, fever, and abdominal cramps. Severity of the disease ranges from mild to very severe diarrhea. Diarrhea is bloody 25-50 percent of the time and most often contains mucus. Rectal spasms, medically termed “tenesmus,” are common. The illness starts 12 hours to 6 days, usually 1-2 days, after exposure (MMWR Surveillance Summaryes, 1996). Dehydration is also a common symptom of Shigella infection.
Shigellosis usually resolves in 5 to 7 days, although it may be several months before a victim’s bowel habits are entirely normal. In some persons, especially young children, the elderly, and immune compromised persons, the diarrhea can be so severe that the patient needs to be hospitalized. The hospitalization rate for shigellosis is estimated to be in excess of 50,000 per year in the United States (Mead, et al., 1999).
In addition to common symptoms of Shigellosis, some children who run high fevers have seizures, although it is not known whether the seizures are a result of the fever or the Shigella infection itself (Mayo Clinic, 2007, April 14).
What are the serious and long-term risks of Shigella infection?
Shigellosis is more severe than other forms of gastroenteritis. This is because when Shigella bacteria multiply in the human gut they invade cells and result in much tissue destruction (Philpott, Edgeworth & Sansonetti, 2000). Also, many strains produce a toxin called “shiga toxin” which is very potent and destructive. Shiga toxin is very similar to the verotoxin of E. coli O157:H7.
More than one million deaths occur in the developing world yearly due to infections with Shigella. The victims are mostly children (Philpott, Edgeworth & Sansonetti, 2000). In the United States, it is estimated that about 700 persons die yearly from shigellosis (Mead, 1999). Small children and the elderly are at greatest risk to experience mortality from a Shigella infection.
Complications of shigellosis include severe dehydration, seizures in small children, rectal bleeding, and invasion of the blood stream by the bacterium. Other complications include:
Reiter’s Syndrome (Reactive Arthritis). Up to 3 percent of persons who are infected with Shigella may later develop a syndrome that includes joint pain and swelling, irritation of the eyes, and sometimes painful urination. This is a reaction to the previous gastroenteritis and is called “reactive arthritis.” It occurs because of protein mimicry; basically, the immune system, intending to fight Shigella, attacks the self (Ringrose, 2001). Reiter’s Syndrome is most common in persons with the HLA-B27 genetic makeup. (Testing for this is readily available.) Reiter’s Syndrome can last for months or years, can lead to chronic arthritis, and may be difficult to treat.
Toxic megacolon. Toxic megacolon is characterized by abdominal pain and swelling, fever, and weakness. This complication occurs when a person’s colon becomes paralyzed, preventing them from having bowel movements or from passing gas. Without treatment, a person’s colon may rupture, causing a life-threatening condition that requires emergency surgery (Mayo Clinic, 2007, April 14).
Hemolytic uremic syndrome (HUS). HUS is a rare complication of shigellosis, more commonly caused by E. coli O157:H7 (Mayo Clinic, 2007, April 14). Development of HUS usually results in a low red blood cell count (hemolytic anemia), low platelet count (thrombocytopenia) and acute kidney failure. The kidney, pancreas, and brain are the organs most likely to be damaged during the acute phase of HUS.