Shigellosis
Shigellosis
Definition
Shigellosis is an infection of the intestinal tract by a group of bacteria called Shigella. The bacteria is named in honor of Shiga, a Japanese researcher, who discovered the organism in 1897. The major symptoms are diarrhea, abdominal cramps, fever, and severe fluidloss (dehydration ). Four different groups of Shigella can affect humans; of these, S. dysenteriae generally produces the most severe attacks, and S. sonnei the mildest.
Description
Shigellosis is a well-known cause of traveler's diarrhea and illness throughout the world. Shigella are extremely infectious bacteria, and ingestion of just 10 organisms is enough to cause severe diarrhea and dehydration. Shigella accounts for 10-20% of all cases of diarrhea worldwide, and in any given year infects over 140 million persons and kills 600,000, mostly children and the elderly. The most serious form of the disease is called dysentery, which is characterized by severe watery (and often blood- and mucous-streaked) diarrhea, abdominal cramping, rectal pain, and fever. Shigella is only one of several organisms that can cause dysentery, but the term bacillary dysentery is usually another name for shigellosis.
Most deaths are in less-developed or developing countries, but even in the United States, shigellosis can be a dangerous and potentially deadly disease. Poor hygiene, overcrowding, and improper storage of food are leading causes of infection. The following statistics show the marked difference in the frequency of cases between developed and less-developed countries; in the United States, about 30,000 individuals are hit by the disease each year or about 10 cases/100,000 population. On the other hand, infection in some areas of South America is 1,000 times more frequent. Shigellosis is most common in children below age five, and occurs less often in adults over 20.
Causes and symptoms
Shigella share several of the characteristics of a group of bacteria that inhabit the intestinal tract. E coli, another cause of food-borne illness, can be mistaken for Shigella both by physicians and the laboratory. Careful testing is needed to assure proper diagnosis and treatment.
Shigella are very resistant to the acid produced by the stomach, and this allows them to easily pass through the gastrointestinal tract and infect the colon (large intestine). The result is a colitis that produces multiple ulcers, which can bleed. Shigella also produce a number of toxins (Shiga toxin and others) that increase the amount of fluid secretion by the intestinal tract. This fluid secretion is a major cause of the diarrhea symptoms.
Shigella infection spreads through food or water contaminated by human waste. Sources of transmission are:
- contaminated milk, ice cream, vegetables and other foods which often cause epidemics
- household contacts (40% of adults and 20% of children will develop infection from such a source)
- poor hygiene and overcrowded living conditions
- day care centers
- sexual practices which lead to oral-anal contact, directly or indirectly
Symptoms can be limited to only mild diarrhea or go on to full-blown dysentery. Dehydration results from the large fluid losses due to diarrhea, vomiting, and fever. Inability to eat or drink worsens the situation.
In developed countries, most infections are of the less severe type, and are often due to S. sonnei. The period between infection and symptoms (incubation period) varies from one to seven days. Shigellosis can last from a few days to several weeks, with an average of seven days.
Complications
Areas outside the intestine can be involved, including:
- nervous system (irritation of the meninges or meningitis, encephalitis, and seizures)
- kidneys (producing hemolytic uremic syndrome or HUS which leads to kidney failure)
- joints (leading to an unusual form of arthritis called Reiter's syndrome)
- skin (rash)
One of the most serious complications of this disease is HUS, which involves the kidney. The main findings are kidney failure and damage to red blood cells. As many as 15% of patients die from this complication, and half the survivors develop chronic kidney failure, requiring dialysis.
Another life-threatening condition is toxic megacolon. Severe inflammation causes the colon to dilate or stretch, and the thin colon wall may eventually tear. Certain medications (particularly those that diminish intestinal contractions) may increase this risk, but this interaction is unclear. Clues to this diagnosis include sudden decrease in diarrhea, swelling of the abdomen, and worsening abdominal pain.
Diagnosis
Shigellosis is one of the many causes of acute diarrhea. Culture (growing the bacteria in the laboratory) of freshly obtained diarrhea fluid is the only way to be certain of the diagnosis. But even this is not always positive, especially if the patient is already on antibiotics. Shigella are identified by a combination of their appearance under the microscope and various chemical tests. These studies take several days, so quicker means to recognize the bacteria and its toxins are being developed.
Treatment
The first aim of treatment is to keep up nutrition and avoid dehydration. Ideally, a physician should be consulted before starting any treatment. Antibiotics may not be necessary, except for the more severe infections. Many cases resolve before the diagnosis is established by culture. Medications that control diarrhea by slowing intestinal contractions can cause problems and should be avoided by patients with bloody diarrhea or fever, especially if antibiotics have not been started.
Rehydration
The World Health Organization (WHO) has developed guidelines for a standard solution taken by mouth, and prepared from ingredients readily available at home. This Oral Rehydration Solution (ORS) includes salt, baking powder, sugar, orange juice, and water. Commercial preparations, such as Pedialyte, are also available. In many patients with mild symptoms, this is the only treatment needed. Severe dehydration usually requires intravenous fluid replacement.
Antibiotics
In the early and mid-1990s, researchers began to realize that not all cases of bacterial dysentery needed antibiotic treatment. Many patients improve without such therapy, and therefore these drugs are indicated only for treatment of moderate or severe disease, as found in the tropics. Choice of antibiotic is based on the type of bacteria found in the geographical area and on laboratory results. Recommendations as of 1997 include ampicillin, sulfa derivatives such as Trimethoprim-Sulfamethoxazole (TMP-SMX) sold as Bactrim, or fluoroquinolones (such as Ciprofloxacin which is not FDA approved for use in children).
Prognosis
Many patients with mild infections need no specific treatment and recover completely. In those with severe infections, antibiotics will decrease the length of symptoms and the number of days bacteria appear in the feces. In rare cases, an individual may fail to clear the bacteria from the intestinal tract; the result is a persistent carrier state. This may be more frequent in AIDS (Acquired Immune Deficiency Syndrome) patients. Antibiotics are about 90% effective in eliminating these chronic infections.
KEY TERMS
Dysentery— A disease marked by frequent watery bowel movements, often with blood and mucus, and characterized by pain, urgency to have a bowel movement, fever, and dehydration.
Traveler's diarrhea— An illness due to infection from a bacteria or parasite that occurs in persons traveling to areas where there is a high frequency of the illness. The disease is usually spread by contaminated food or water.
Oral Rehydration Solution(ORS)— A liquid preparation developed by the World Health Organization that can decrease fluid loss in persons with diarrhea. Originally developed to be prepared with materials available in the home, commercial preparations have recently come into use.
Antibiotic— A medication that is designed to kill or weaken bacteria.
Anti-motility medications— Medications such as loperamide (Imodium), dephenoxylate (Lomotil), or medications containing codeine or narcotics which decrease the ability of the intestine to contract. These may worsen the condition of a patient with dysentery or colitis.
Food-borne illness— A disease that is transmitted by eating or handling contaminated food.
Fluoroquinolones— A relatively new group of antibiotics that have had good success in treating infections with many gram-negative bacteria, such as Shigella. One drawback is that they should not be used in children under 17 years of age, because of possible effect on bone or cartilage growth.
Dialysis— A form of treatment for patients with kidneys that do not function properly. The treatment removes toxic wastes from the body that are normally removed by the kidneys.
Colitis— Inflammation of the colon or large bowel which has several causes. The lining of the colon becomes swollen, and ulcers often develop. The ability of the colon to absorb fluids is also affected, and diarrhea often results.
Carrier state— The continued presence of an organism (bacteria, virus, or parasite) in the body that does not cause symptoms, but is able to be transmitted and infect other persons.
Stool— Passage of fecal material; a bowel movement.
Meninges— Outer covering of the spinal cord and brain. Infection is called meningitis, which can lead to damage to the brain or spinal cord and lead to death.
In patients who have suffered particularly severe attacks, some degree of cramping and diarrhea can last for several weeks. This is usually due to damage to the intestinal tract, which requires some time to heal. Since antibiotics can also produce a form of colitis, this must be considered as a possible cause of persistent or recurrent symptoms.
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.
Traveler's diarrhea (TD)
Shigella accounts for about 10% of diarrhea illness in travelers to Mexico, South America, and the tropics. Most cases of TD are more of a nuisance than a life-threatening disease. However, bloody diarrhea is an indication that Shigella may be responsible.
In some cases though, aside from ruining a well deserved vacation, these infections can interrupt business conference schedules and, in the worst instances, lead to a life-threatening illness. Therefore, researchers have tried to find a safe, yet effective, way of preventing TD. Of course the best prevention is to follow closely the rules outlined by the WHO and other groups regarding eating fresh fruits, vegetables, and other foods.
One safe and effective method of preventing TD is the use of large doses of Pepto Bismol. Tablets are now available which are easier for travel; usage must start a few days before departure. Patients should be aware that Bismuth will turn bowel movements black.
Antibiotics have also proven to be highly effective in preventing TD. They can also produce significant side effects, and therefore a physician should be consulted before use. Like Pepto Bismol, antibiotics need to be started before beginning travel.
Resources
ORGANIZATIONS
Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. 〈http://www.cdc.gov〉.
Shigellosis
Shigellosis
Definition
Shigellosis is an infection of the intestinal tract by a group of bacteria called Shigella.
Description
Shigellosis is a well-known cause of traveler's diarrhea and illness throughout the world. The major symptoms of shigellosis are diarrhea, abdominal cramps, fever , and severe fluid loss (dehydration ). The bacteria causing shigellosis is named after Shiga, a Japanese researcher, who discovered the organism in 1897. Four different groups of Shigella can affect humans; of these, S. dysenteriae generally produces the most severe attacks, and S. sonnei the mildest. Shigella are extremely infectious bacteria, and ingestion of just 10 organisms is enough to cause dysentery. The most serious form of the disease is called dysentery, which is characterized by severe watery (and often blood- and mucus-streaked) diarrhea, abdominal cramping, rectal pain , and fever. Shigella is only one of several organisms that can cause dysentery, but the term bacillary dysentery is usually another name for shigellosis.
Demographics
Shigella accounts for 10 to 20 percent of all cases of diarrhea worldwide, and in any given year infects over 140 million persons and kills 600,000, mostly children and the elderly.
Most deaths are in less-developed or developing countries, but even in the United States, shigellosis can be a dangerous and potentially deadly disease. Poor hygiene, overcrowding, and improper storage of food are leading causes of infection. Shigellosis is often passed within families when young children are not yet toilet-trained and hand washing is poorly done. The following statistics show the marked difference in the frequency of cases between developed and less-developed countries: in the United States, about 30,000 individuals are hit by the disease each year or about 10 cases per 100,000 population. By contrast, infection in some areas of South America is 1,000 times more frequent. Shigellosis is most common in children below the age of five years and occurs less often in adults over 20.
Causes and symptoms
Shigella share several of the characteristics of a group of bacteria that inhabit the intestinal tract. E. coli, another cause of food-borne illness, can be mistaken for Shigella both by physicians and the laboratory. Careful testing is needed to assure proper diagnosis and treatment.
Shigella are very resistant to the acid produced by the stomach, and this allows them to easily pass through the gastrointestinal tract and infect the colon (large intestine). The result is a colitis that produces multiple ulcers, which can bleed. Shigella also produce a number of toxins (Shiga toxin and others) that increase the amount of fluid secretion by the intestinal tract. This fluid secretion is a major cause of the diarrhea symptoms.
Shigella infection spreads through food or water contaminated by human waste. Sources of transmission are as follows:
- contaminated milk, ice cream, vegetables, and other foods which often cause epidemics
- household contacts (40% of adults and 20% of children develop infection from such a source)
- poor hygiene and overcrowded living conditions
- daycare centers
- sexual practices which lead to oral-anal contact, directly or indirectly
Symptoms can be limited to mild diarrhea or develop into dysentery. Dehydration results from the large fluid losses due to diarrhea, vomiting , and fever. Inability to eat or drink worsens the situation.
In developed countries, most infections are of the less severe type and are often due to S. sonnei. The period between infection and symptoms (incubation period) varies from one to seven days. Shigellosis can last from a few days to several weeks, with the average duration seven days.
Complications
Areas outside the intestine can be involved, including the following:
- nervous system (irritation of the meninges or meningitis , encephalitis , and seizures)
- kidneys (producing hemolytic uremic syndrome or HUS which leads to kidney failure)
- joints (leading to an unusual form of arthritis called Reiter's syndrome)
- skin (rash)
One of the most serious complications of this disease is HUS, which involves the kidney. The main findings are kidney failure and damage to red blood cells. As many as 15 percent of patients die from this complication, and half the survivors develop chronic kidney failure, requiring dialysis.
Another life-threatening condition is toxic megacolon. Severe inflammation causes the colon to dilate or stretch, and the thin colon wall may eventually tear. Certain medications (particularly those that diminish intestinal contractions) may increase this risk, but this interaction is unclear. Clues to this diagnosis include sudden decrease in diarrhea, swelling of the abdomen, and worsening abdominal pain.
Diagnosis
Shigellosis is one of the many causes of acute diarrhea. Culture (growing the bacteria in the laboratory) of freshly obtained diarrhea fluid is the only way to be certain of the diagnosis. But even this is not always positive, especially if the patient is already on antibiotics . Shigella are identified by their appearance under the microscope, along with various chemical tests. These studies take several days.
Treatment
The first aim of treatment is to keep up nutrition and avoid dehydration. Ideally, a physician should be consulted before starting any treatment. Antibiotics may not be necessary, except for the more severe infections. Many cases resolve before the diagnosis is established by culture. Medications that control diarrhea by slowing intestinal contractions can cause problems and should be avoided by patients with bloody diarrhea or fever, especially if antibiotics have not been started.
Rehydration
The World Health Organization (WHO) has developed guidelines for a standard solution taken by mouth and prepared from ingredients readily available at home. This oral rehydration solution (ORS) includes salt, baking powder, sugar, orange juice, and water. Commercial preparations, such as Pedialyte, are also available. In many patients with mild symptoms, this is the only treatment needed. Severe dehydration usually requires intravenous fluid replacement.
Antibiotics
Patients who have very mild cases of shigellosis may improve without any antibiotic therapy; therefore, these drugs are indicated only for treatment of moderate or severe disease, as found in the tropics. Choice of antibiotic is based on the type of bacteria found in the geographical area and on laboratory results. Recommended antibiotics include ampicillin, sulfa derivatives such as trimethoprim-sulfamethoxazole (TMP-SMX) sold as Bactrim, or fluoroquinolones, such as Ciprofloxacin.
Prognosis
Many patients with mild infections need no specific treatment and recover completely. In those with severe infections, antibiotics decrease the length of symptoms and the number of days bacteria appear in the feces. In rare cases, an individual may fail to clear the bacteria from the intestinal tract; the result is a persistent carrier state. This may be more frequent in patients with acquired immune deficiency syndrome (AIDS ). Antibiotics are about 90 percent effective in eliminating these chronic infections.
In patients who have suffered particularly severe attacks, some degree of cramping and diarrhea can last for several weeks. This is usually due to damage to the intestinal tract, which requires some time to heal. Since antibiotics can also produce a form of colitis, which may cause persistent or recurrent symptoms.
Prevention
Shigellosis is an extremely contagious disease; good hand washing techniques (especially after toileting young children or changing diapers) and proper precautions in food handling help in avoiding the spread of infection. Children in daycare centers need to be reminded about hand washing during an outbreak to minimize contagion. Shigellosis in schools or daycare settings almost always disappears when holiday breaks occur, which severs the chain of transmission.
Traveler's diarrhea (TD)
Shigella accounts for about 10 percent of diarrhea illness in travelers to Mexico, South America, and the tropics. Most cases of TD are more of a nuisance than a life-threatening disease.
In some cases, though, aside from ruining vacation plans, these infections can interrupt business conference schedules and, in the worst instances, lead to a life-threatening illness. Therefore, researchers have tried to find a safe, yet effective, way of preventing TD. Of course the best prevention is to follow closely the rules outlined by the WHO and other groups regarding eating fresh fruits, vegetables, and other foods.
One safe and effective method of preventing TD is the use of large doses of Pepto Bismol. Tablets are easier for use during travel; usage must start a few days before departure. Patients should be aware that bismuth turns bowel movements black.
Antibiotics have also proven highly effective in preventing TD. They can also produce significant side effects. Therefore, a physician should be consulted before use. Like Pepto Bismol, antibiotics need to be started before beginning travel.
KEY TERMS
Antibiotics —Drugs that are designed to kill or inhibit the growth of the bacteria that cause infections.
Antimotility drug —A medication, such as loperamide (Imodium), dephenoxylate (Lomotil), or medications containing codeine or narcotics that decrease the ability of the intestine to contract.
Carrier state —The continued presence of an organism (bacteria, virus, or parasite) in the body that does not cause symptoms, but is able to be transmitted and infect other persons.
Colitis —Inflammation of the colon (large intestine).
Dialysis —A process of filtering and removing waste products from the bloodstream, it is used as a treatment for patients whose kidneys do not function properly. Two main types are hemodialysis and peritoneal dialysis. In hemodialysis, the blood flows out of the body into a machine that filters out the waste products and routes the cleansed blood back into the body. In peritoneal dialysis, the cleansing occurs inside the body. Dialysis fluid is injected into the peritoneal cavity and wastes are filtered through the peritoneum, the thin membrane that surrounds the abdominal organs.
Dysentery —A disease marked by frequent watery bowel movements, often with blood and mucus, and characterized by pain, urgency to have a bowel movement, fever, and dehydration.
Fluoroquinolones —A relatively new group of antibiotics used to treat infections with many gramnegative bacteria, such as Shigella . One drawback is that they should not be used in children under 17 years of age, because of possible effect on bone or cartilage growth.
Food-borne illness —A disease that is transmitted by eating or handling contaminated food.
Meninges —The three-layer membranous covering of the brain and spinal cord, composed of the dura mater, arachnoid, and pia mater. It provides protection for the brain and spinal cord, as well as housing many blood vessels and participating in the appropriate flow of cerebrospinal fluid.
Oral rehydration solution (ORS) —A liquid preparation of electrolytes and glucose developed by the World Health Organization that can decrease fluid loss in persons with diarrhea. Originally developed to be prepared with materials available in the home, commercial preparations have recently come into use.
Stool —The solid waste that is left after food is digested. Stool forms in the intestines and passes out of the body through the anus.
Traveler's diarrhea —An illness due to infection from a bacteria or parasite that occurs in persons traveling to areas where there is a high frequency of the illness. The disease is usually spread by contaminated food or water.
Parental concerns
Parents of children suffering from shigellosis need to follow closely their healthcare provider's directions for preventing dehydration. Excellent hand washing is crucial to prevent the spread of the infection throughoutfamily members. This is particularly important while helping to toilet train a child or while changing diapers.
Resources
BOOKS
Cleary, Thomas G. "Shigella." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2004.
WEB SITES
Kroser, Joyann A. "Shigellosis." eMedicine, May 17, 2002. Available online at <www.emedicine.com/med/topic2112.htm> (accessed December 30, 2004).
"Shigellosis." New York State Info for Consumers. Available online at <www.health.state.ny.us/nysdoh/Communicable_diseases/en/shig.htm> (accessed December 30, 2004).
David Kaminstein, MD Rosalyn Carson-DeWitt, MD
Shigellosis
Shigellosis
Disease History, Characteristics, and Transmission
Introduction
Shigellosis is an infection of the gastrointestinal tract that arises when a person is infected with bacteria in the genus Shigella. These bacteria are transmitted among a human population when people ingest food or drink contaminated with fecal matter from an infected person. Following a 24-hour incubation period, most patients experience nausea, diarrhea, fever, and stomach cramps. While most people recover from shigellosis within a week without treatment, severe cases require antibiotics in order to recover.
Shigellosis occurs worldwide. It is most prevalent in developing nations in which epidemics often occur. Anyone can get shigellosis, but it is more common among people with poor hygiene, such as young children, as well as people living or traveling through areas with dense living conditions and poor sanitation. Since there is no vaccine against shigellosis, prevention is achieved through improving sanitation and hygiene, washing hands prior to handling food, washing food prior to eating, and boiling drinking water. Shigellosis can become a major issue during emergency situations, such as mass evacuations when many people temporarily live together in poor conditions. There is also potential for Shigella bacteria to be used for biological warfare.
Disease History, Characteristics, and Transmission
Shigellosis is a gastrointestinal infection caused by bacteria from the genus Shigella. There are four species of Shigella, S. dysenteriae, S. flexneri, S. boydii, and S. sonnei. Shigella infect humans and other primates. Bacteria from this genus were first identified by the Japanese scientist Kiyoshi Shiga (1871–1957) in 1897 after he isolated S. dysenteriae, which was causing dysentery, a gastrointestinal disease, in infected people.
Shigellosis is usually transmitted via the fecal-oral route, that is, people become infected after ingesting food or water contaminated with infected feces. Inadequate handwashing after using the toilet, or changing a baby diaper, followed by food or water handling leads to contamination of food and drink. This is a very common method for person-to-person transmission of the Shigella bacteria. Flies are also a source of transmission as they travel between infected fecal matter and food or drink. Food and water may also become contaminated when vegetables are grown in soil containing sewage, or when people defecate in bodies of water.
Shigellosis leads to the development of gastrointestinal symptoms, such as dysentery. Symptoms include diarrhea, fever, stomach cramps, and nausea. Symptoms generally begin a day or two after the bacteria is contracted, although it may take up to a week for a person to fall ill. Although recovery is usual in most cases, infection with S. flexneri may result in long-term problems such as arthritis, eye irritation, and painful urination. This is known as Reiter's syndrome and may continue for months to years.
Scope and Distribution
Shigellosis occurs worldwide. It is particularly common in developing countries in which the bacteria are present in almost all communities most of the time. Furthermore, S. dysenteriae type 1, although rare in the United States, is a major health concern for many developing countries. In the United States, the most common forms of Shigella are S. sonnei, which causes over two-thirds of shigellosis infections, and S. flexneri, which causes most of the remaining cases. The annual number of cases of shigellosis in the United States ranges from as few as 1,000 to as many as 18,000, although this number is likely to be underestimated, since many mild cases go undiagnosed.
Although anyone is capable of contracting shigellosis, some people are more susceptible. This includes toddlers who usually aren't fully toilet trained. In addition, childcare facilities provide a setting in which the bacteria can spread through a number of children in a short period of time. Foreign travelers are also more susceptible to infection, if they travel through regions in which the disease is prevalent and sanitation methods are poor. Persons living together in crowded conditions or institutions, such as prisons, are also more susceptible to developing the disease, most likely as a result of poor hygiene.
WORDS TO KNOW
BIOLOGICAL WEAPON: A weapon that contains or disperses a biological toxin, disease-causing microorganism, or other biological agent intended to harm or kill plants, animals, or humans.
DYSENTERY: Dysentery is an infectious disease that has ravaged armies, refugee camps, and prisonerof-war camps throughout history. The disease still is a major problem in developing countries with primitive sanitary facilities.
FECAL-ORAL TRANSMISSION: The spread of disease through the transmission of minute particles of fecal material from one organism to the mouth of another organisms. This can occur by drinking contaminated water, eating food that was exposed to animal or human feces (perhaps by watering plants with unclean water), or by the poor hygiene practices of those preparing food.
REITER'S SYNDROME: Reiter's syndrome (also called Reiter syndrome, Reiter disease, or reactive arthritis), named after German doctor Hans Reiter (1881–1969), is form of arthritis (joint inflammation) that appears in response to bacterial infection in some other part of the body.
The transmission of shigellosis is enhanced in conditions of poor sanitation and close human contact. These conditions are common in developing countries where funding for sanitation may be lacking and residents may not be educated about the need for hygiene. In addition, these conditions are also common in emergency situations, for example, after a hurricane or earthquake, when many people are often housed together temporarily.
Treatment and Prevention
Shigellosis is a bacterial disease and is treated with anti-biotics. However, mild cases of shigellosis do not require antibiotics, since a full recovery usually occurs within a week. However, people suffering from severe infections, or those who have a compromised immune system that prevents them fighting the infection themselves, usually require a course of antibiotics. The most common anti-biotics used are ampicillin, trimethoprim/sulfamethoxazole, nalidixic acid, or ciprofloxacin. However, Shigella bacteria are beginning to develop resistance to antibiotics, which reduces the effectiveness of treatment. In order to combat this problem, health officials are trying to reduce the reliance on antibiotics by limiting their use.
Other treatments are aimed at the symptoms of the infection. These may include administering fluids to prevent or reverse dehydration and medicines to reduce temperature and prevent convulsions. Antidiarrheal agents are not recommended by the Centers for Disease Control and Prevention (CDC), since they are likely to make the illness worse.
While research on the development of a vaccine against shigellosis has been underway since 1940, no vaccine is currently available. As a result, preventative measures center around avoiding ingestion of Shigella bacteria. In developed countries, in which sanitation is usually good and water is clean, prevention is best achieved through handwashing and improving personal hygiene. However, in developing countries, in which sanitation is often poor and clean water is not readily available, improvements in sanitation methods and increased availability of clean water are necessary to prevent community-wide spread of the bacteria. In addition, people with shigellosis can best prevent spreading the disease to others by washing their hands after going to the toilet, avoiding preparing food for others, and avoiding public swimming areas.
Impacts and Issues
Shigellosis is common in developing countries due to poor sanitation and, in some cases, overcrowding. However, situations such as this can arise in developed nations when natural disasters, such as hurricanes, tornadoes, and floods, cause mass evacuation of people. Often mass evacuations result in a large number of people having to live in close quarters. Since these living quarters are often temporary and are usually not made to house large numbers of people, sanitation standards tend to be lower than normal. The combination of high density living with poor sanitation increases the risk of shigellosis within the population.
Another potential issue concerning Shigella bacteria is its use as a biological weapon. Shigella has been considered a potential agent of biological warfare since at least 1932 when the Japanese investigated its potential. Biological warfare involves using pathogens or toxins to cause mass death and disease among humans, animals, or plants during war. Biological terrorism is similar, except the pathogens and toxins are used for terrorist purposes. In addition to Shigella, other bacterial agents, such as Salmonella and Escherichia coli, are considered potential biological threats. Shigella can potentially be spread via a community's water supply, which could cause many cases of shigellosis. In 1996, one case of S. dysenteriae caused an outbreak of shigellosis. A worker from Dallas contaminated muffins and doughnuts with Shigella prior to feeding coworkers. This resulted in a number of the workers developing shigellosis, and the perpetrator was jailed.
See AlsoAntibiotic Resistance; Bacterial Disease; Bioterrorism; Childhood Infectious Diseases, Immunization Impacts; Cohorted Communities and Infectious Disease; Dysentery; Salmonella Infection (Salmonellosis).
BIBLIOGRAPHY
Books
Fong, I. W., and K. Alibek. Bioterrorism and Infectious Agents: A New Dilemma for the 21st Century. New York: Springer Science, 2005.
Mandell, G. L., J. E. Bennett, and R. Dolin. Principles and Practice of Infectious Diseases. 6th ed. Philadelphia: Elsevier, 2004.
Web Sites
Baylor College of Medicine. “Potential Bioterrorism Agents.” July 5, 2006. <http://www.bcm.edu/molvir/eidbt/eidbt-mvm-pbt.htm> (accessed March 12, 2007).
Centers for Disease Control and Prevention. “Hurricane Recovery Information.” September 16, 2005. <http://www.bt.cdc.gov/disasters/hurricanes/katrina/shigella.asp> (accessed March 12, 2007).
Centers for Disease Control and Prevention. “Shigellosis.” October 13, 2005. <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/shigellosis_g.htm> (accessed March 12, 2007).
New York State, Department of Health. “Shigellosis.” June 2004. <http://www.health.state.ny.us/diseases/communicable/shigellosis/fact_sheet.htm> (accessed March 12, 2007).
Shigellosis
SHIGELLOSIS
Shigellosis, also known as bacillary dysentery, is a common food-borne infection that causes diarrhea with fever, toxemia, and general prostration. Blood and mucous are often mixed with the loose, watery stools, indicating severe inflammation of the intestinal lining. The causative organisms are several varieties of the genus Shigella. Infection is transmitted by active or convalescent cases (e.g., person to person). Food handlers working in unhygienic kitchens or restaurants sometimes become the index case for large epidemics. The incubation period is short, from one to three days, so it can be relatively easy to trace the source of an outbreak. The diarrhea and other symptoms usually run their course in a week or so, but the infectious agents can persist in feces for several weeks—which is the reason that food handlers should not be allowed to return to work, preferably for several weeks or until stool examinations for Shigella organisms are negative.
Control of shigella dysentery can be difficult, especially in settings such as military campaigns. Meticulous hygiene in all aspects of food handling and meal preparation are essential; everyone in the kitchen must scrupulously observe the rules for hand washing with warm water and soap after visiting the toilet and before handling food. The use of disposable plastic gloves is desirable, but these must be changed frequently. Flies must be kept out of kitchen areas.
Shigellosis is a notifiable disease in many jurisdictions, so local public health authorities will ensure that suspect premises and all persons working in such premises are inspected. Cases are treated by fluid and salt replacement, and often benefit from antibiotics.
John M. Last
(see also: Communicable Disease Control; Food-Borne Diseases; Regulations Affecting Restaurants )