What is Shigellosis (Bacillary Dysentery)?
Shigellosis is an infectious disease caused by a group of bacteria called Shigella that causes bacterial dysentery. These bacterium cause disease by penetrating the lining of the large intestine, causing swelling and sores. This causes diarrhoea, fever, and stomach cramps 1-2 days after initial exposure.
Pathogenesis of shigella
The Shigella germ is actually a family of bacteria that can cause diarrhoea in humans. They are microscopic living creatures that pass from person to person. There are several different kinds of Shigella bacteria: Shigella sonnei, accounts for over two-thirds of the shigellosis in the United States. A second type, Shigella flexneri, accounts for almost all of the rest. Other types of Shigella (such as Shigella dysenteriae and Shigella boydii.
Shigella in stool sample
On a global scale, of the estimated 165 million Shigella diarrhoeal episodes estimated to occur each year, 99% occur in developing countries, mainly in children. In 1999, a systematic review reported Shigella to be responsible for 1.1 million deaths per year, 61% of which in children less than 5 years of age, based on prevalence in diarrhoea cases and limited data on case-fatality rates amongst hospitalised children.
In 2013, these estimates were revised using a similar modelling strategy, but with updated mortality risk data, suggesting between 28,000 and 48,000 deaths annually amongst children under 5 years due to Shigellosis. In 2016, a quantitative molecular analysis from the Global Enteric Multicentre Study (GEMS) identified an increased burden of Shigellosis and reported it as the leading pathogen among the top six attributable pathogens causing childhood diarrhoea.
The GEMS data and consideration of the indirect risks of malnutrition arising in relation to diarrhoeal episodes may lead to further revisions of Shigella-attributable mortality estimates. Shigellosis occurs predominantly in developing countries due to overcrowding and poor sanitation. Infants, non-breast fed children, children recovering from measles, malnourished children, and adults older than 50 years have a more severe illness and a greater risk of death.
Medical writers have described dysentery or “the flux” since ancient times, but the bacterial form of the disease was not clearly distinguished until late in the nineteenth century. Dysentery ravaged Persian armies invading Greece in 480 B.C., and the disease has always been a companion of armies, often proving more destructive than enemy action. This disease was, and remains, common among both rural and urban poor people around the world. An epidemic of what must have been shigellosis swept France in 1779, causing especially severe damage in some rural areas of the western part of the country. Troop movements for a planned invasion of England helped spread the disease. At least 175,000 people died, with some 45,000 deaths in Brittany alone. Children constituted the majority of the fatalities.
During the U.S. Civil War, Union soldiers had annual morbidity rates of 876 per 1,000 from dysentery, and annual mortality rates of 10 per 1,000. Dysentery outbreaks were problems for all belligerents in World War I, especially in the Gallipoli and Mesopotamian campaigns.
Japanese bacteriologist Kiyoshi Shiga isolated S. dysenteriae in 1898 and confirmed its role as a pathogen. The other species were discovered early in the twentieth century, and much re-search has been directed to immunologic studies of various strains. The role of Campylobacter species as common human pathogens has been recognized only since the 1970’s.
What Causes Bacillary Dysentery (Shigellosis)?
- The shigella bacillus, a bacterium that invades the lining of the colon, is one of several infections that can cause dysentery.
- Other causes of dysentery include the parasite amoeba and the bacteria coli, Yersinia, and others.
- The shigella bacillus is typically spread via contact with the fecal matter of an infected person.
- Failure to wash the hands thoroughly after a bowel movement may help to transmit shigellosis.
- Flies may spread the bacteria from feces (more common in areas with poor sanitation.)
- Contaminated food or water may spread infection.
- Being a toddler. Shigella infection is most common in children between the ages of 2 and 4.
- Living in group housing or participating in group activities. Close contact with other people spreads the bacteria from person to person. Shigella outbreaks are more common in child care centers, community wading pools, nursing homes, jails and military barracks.
- Living or traveling in areas that lack sanitation. People who live or travel in developing countries are more likely to contract shigella infection.
- Being a sexually active gay male. Men who have sex with men are at higher risk because of direct or indirect oral-anal contact.
The main symptom of dysentery is frequent near-liquid diarrhea flecked with blood, mucus, or pus. Other symptoms include:
- Sudden onset of high fever and chills
- Abdominal pain
- Cramps and bloating
- Flatulence (passing gas)
- Urgency to pass stool
- Feeling of incomplete emptying
- Loss of appetite
- Weight loss
- Other symptoms may be intermittent and may include recurring low fevers, abdominal cramps, increased gas, and milder and firmer diarrhea
- You may feel weak and anemic, or lose weight over a prolonged period
Bacillary dysentery symptoms begin within 2 to 10 days of infection. In children, the illness starts with fever, nausea, vomiting, abdominal cramps, and diarrhea. Episodes of diarrhea may increase to as much as once an hour with blood, mucus, and pus in the child’s stool. Vomiting may result in rapid and severe dehydration, which may lead to shock and death if not treated.
Signs of dehydration include an extremely dry mouth, sunken eyes, and poor skin tone. Children and infants will be thirsty, restless, irritable, and possibly lethargic. Children may also have sunken eyes and may not be able to produce tears or urine, the latter appearing very dark and concentrated.
Complications are uncommon but may include the following:
- Dehydration and electrolyte disturbance may occur. Occasionally where not rectified, this can have fatal consequences. Infants, the elderly and those with immunological compromise are more likely to have more severe disease and to require admission to hospital for rehydration. Pregnant women are also more at risk of dehydration.
- Bacteraemia is more common in malnourished children and carries a high mortality.
- Seizures may occur in young children and are common where there is fever.
- Rectal prolapse. In this condition, straining during bowel movements may cause the mucous membrane or lining of the rectum to move out through the anus.
- Haemolytic uraemic syndrome may (rarely) complicate infections, usually those with dysenteriae and mostly affecting young children or the elderly. It is more commonly a complication of E. coli O157 and leads to haemolytic anaemia, thrombocytopenia and acute kidney injury.
- Reactive arthritis (or Reiter’s syndrome when arthritis is combined with uveitis and urethritis) can occur. It is most common in men aged 20-40 and with the HLA-B27 antigen. This is most often associated with flexneri infection.
- Toxic megacolon is occasionally a complication of dysenteriae.
Diagnosis of Bacillary Dysentery (Shigellosis)
- Dysentery is distinguished from more routine causes of infectious diarrhea by the presence of blood.
- Physical examination and patient history are needed.
- Stool samples are taken for examination under a microscope and for a laboratory culture to confirm the presence of the shigella
- Colonoscopy to examine the bowels may be performed.
- Blood tests may be taken to look for electrolyte (essential mineral salt) abnormalities or anemia.
How to Treat Bacillary Dysentery (Shigellosis)
- A solution of electrolytes (such as sodium and potassium) and fluids may be administered to treat dehydration, although water or other beverages are usually sufficient. In severe cases, fluids must be replaced intravenously.
- While waiting to see a doctor, prevent dehydration by drinking sports drinks, like Gatorade, or a solution of one teaspoon salt and four teaspoons sugar in one quart of water. It is important to measure accurately: Too much salt may worsen dehydration. Drink one pint each hour while diarrhea persists.
- The following antibiotics are used to treat Shigella dysentery:
- Beta-lactams: Ampicillin, amoxicillin, third-generation cephalosporins (ceﬁxime, ceftriaxone), and pivmecillinam (not available in the United States)
- Quinolones: Nalidixic acid, ciproﬂoxacin, norﬂoxacin, and oﬂoxacin
- Macrolides: Azithromycin
- Others: sulfonamides, tetracycline, cotrimoxazole, and furazolidone.
- Do not take over-the-counter antidiarrheal medications unless otherwise instructed by your doctor. Diarrhea helps rid the body of infectious organisms.
- Although the infection often clears on its own, antibiotics are often given to limit its transmission. These must be taken for the full term prescribed.
- Isolation from others is required to prevent spread of the disease.
- Ensuring the availability of safe drinking water
- Protect drinking water or boil drinking water for 20 minutes if it is suspected to be a source of infection.
- Control flies by screening of doorways and windows, by eliminating fly breeding areas, and by the proper use of insecticides.
- Safe handling and processing of food, including appropriate refrigeration and proper cooking of potentially infected foods
- Control of flies in food handling areas
- Encouragement of breastfeeding of infants
- Hand washing with soap and water
- Safely disposing of human waste
- Voluntary removal of persons with diarrhea from roles as food handlers
- For symptomatic patients, not using recreational water venues (e.g., swimming pools, water parks) or sharing a bath with others until 48 hours after symptoms resolve
- The most important prevention measure in child care facilities is supervised hand washing after toileting and before eating/preparing food. Hand washing upon arrival provides additional protection
- Education about how enteric bacteria are spread, including practices to avoid or reduce the risk for sexual transmission of enteric infections
- Cases abstaining from sexual behavior that is likely to transmit infection during their illness. MSM should avoid direct oral-anal sexual contact especially if sex partners are ill or if there are community outbreaks of enteric infection