Shigella are a group of bacteria that can cause gastroenteritis with dysentery. Diarrhoea is one of the symptoms of gastroenteritis. If the diarrhoea contains blood and mucus, this is known as 'dysentery'. If someone is infected with shigella, the bacteria can pass out in their stools (faeces). Infection with shigella may be caught by drinking water contaminated with infected faeces, eating food prepared using contaminated water or by close contact with someone who has the infection. Infection may occur in people who have travelled to countries with poor sanitation but infection can also be caught in the UK. Treatment is with antibiotics and fluids to prevent or treat dehydration.
What is gastroenteritis and what is dysentery?
Gastroenteritis is an infection of the gut (intestines). The severity can range from a mild tummy upset for a day or two with some mild diarrhoea, to severe diarrhoea and vomiting for several days or longer. Many viruses, bacteria and other microbes (germs) can cause gastroenteritis.
Diarrhoea is defined as 'loose or watery stools (faeces), usually at least three times in 24 hours'. Diarrhoea is one of the symptoms of gastroenteritis. If the diarrhoea contains blood and mucus, this is known as 'dysentery'.
Most cases of gastroenteritis do not lead to bloody diarrhoea and so are not dysentery. However, there are a number of microbes that can cause dysentery. These include Campylobacter, Entamoeba histolytica, Escherichia coli (E. coli), Salmonella and Shigella.
See separate leaflets called 'Campylobacter', 'Amoebiasis', 'E. coli and VTEC O157' and 'Salmonella' that give further details. The rest of this leaflet is just about dysentery caused by Shigella infection.
What is shigella and how do you get it?
Shigella are a group of bacteria that can cause gastroenteritis with dysentery. Dysentery caused by shigella is also known as bacillary dysentery. There are four different species of shigella: Shigella dysenteriae, Shigella flexneri, Shigella boydii and Shigella sonnei.
If someone is infected with shigella, the bacteria can pass out in their stools (faeces). Infection may be passed on to others if drinking water is contaminated with infected faeces or if food is washed in contaminated water and then eaten. Because shigella infection can be passed on by drinking contaminated water or eating contaminated food, shigella can be a cause of food poisoning.
If you have shigella, you may also spread the infection to your close contacts if you do not follow strict hygiene measures to prevent the spread of infection to others (see below).
How common is shigella and who gets it?
Anyone can get shigella infection. However, infection is more common in young children. Commonly, people with shigella infection have travelled to a country where sanitation and hygiene is poor. However, infection can also be caught in the UK. Shigella sonnei is the most common species found in the UK. It tends to cause a mild illness.
What are the symptoms of shigella?
Some people with shigella infection actually have no symptoms. However, the bacteria will still be present in their stools and they can still pass on the infection to other people.
But most people with shigella develop symptoms. Symptoms tend to come on within one to seven days of contact with the bacteria (eg, drinking contaminated water, eating contaminated food). This time period before symptoms appear is known as the 'incubation period'. The usual symptoms are diarrhoea (which will often contain blood and mucus - dysentery), painful abdominal cramps and fever. The symptoms tend to last for around five to seven days.
Symptoms can be severe in some people, particularly the young and the elderly. The diarrhoea can be so bad that it can lead to dehydration. Dehydration is when there is a lack of fluid in the body. You should consult a doctor quickly if you suspect that you or your child are becoming dehydrated. Mild dehydration is common and is usually easily reversed by drinking lots of fluids. Severe dehydration can be fatal unless quickly treated because the organs of your body need a certain amount of fluid to function.
Symptoms of dehydration in children
- Symptoms of dehydration in children include: passing little urine, a dry mouth, a dry tongue and lips, fewer tears when crying, sunken eyes, weakness, being irritable or lethargic.
- Symptoms of severe dehydration in children include: drowsiness, pale or mottled skin, cold hands or feet, very few wet nappies, fast (but often shallow) breathing. This is a medical emergency and immediate medical attention is needed.
Dehydration is more likely to occur in:
- Children under the age of one year (and particularly those under six months old). This is because babies don't need to lose much fluid to lose a significant proportion of their total body fluid.
- Children under the age of one year who were a low birthweight and who have not 'caught up' with their weight.
- An infant that has stopped breast-feeding during their illness.
- Any child who does not drink much when they have shigella infection.
- Any child with severe diarrhoea and vomiting (particularly if they have passed six or more diarrhoeal stools and/or vomited three or more times in the previous 24 hours).
Symptoms of dehydration in adults
- Symptoms of dehydration in adults include: tiredness, dizziness or light-headedness, headache, muscular cramps, sunken eyes, passing little urine, a dry mouth and tongue, weakness, and becoming irritable.
- Symptoms of severe dehydration in adults include: profound apathy, weakness, confusion, rapid heart rate, coma, and producing very little urine. This is a medical emergency.
Dehydration in adults is more likely to occur in:
- Elderly or frail people.
- Pregnant women.
- People with severe diarrhoea and vomiting. In particular, if you are not able to replace the fluid lost with sufficient drinks.
How is shigella diagnosed?
Shigella is usually diagnosed after a sample of your stool is sent to the laboratory for testing. If you have gastroenteritis with blood and mucus in your diarrhoea, you should see a doctor who can arrange for a sample of your stools to be tested.
What is the treatment of shigella in children?
Antibiotics are used to treat shigella infection in children. This is one of the few times that antibiotics are used to treat gastroenteritis infections. It may help to reduce the chance that your child passes on shigella infection to someone else and also may help to reduce the number of days that your child suffers from their symptoms.
The usual antibiotic used is ciprofloxacin. However, the antibiotic may vary depending on advice that your doctor has received from the laboratory specialist who has performed tests on your stool sample.
Fluids to prevent dehydration
You should also encourage your child to take plenty of fluids. The aim is to prevent dehydration (low body fluid). The fluid lost in their vomit and/or diarrhoea needs to be replaced. Your child should continue with their normal diet and usual drinks. In addition, they should also be encouraged to drink extra fluids. However, avoid fruit juices or fizzy drinks as these can make diarrhoea worse.
Babies under six months old are at increased risk of dehydration. Breast- or bottle-feeds should be encouraged as normal. You may find that your baby's demand for feeds increases. You may also be advised to give extra fluids (either water or rehydration drinks) in between feeds.
Rehydration drinks may be suggested by a healthcare professional for children at increased risk of dehydration (see above for whom this may be). They are made from sachets available from pharmacies and on prescription. You should be given instructions about how much to give. Rehydration drinks provide a perfect balance of water, salts, and sugar. The small amount of sugar and salt helps the water to be absorbed better from the gut into the body. Do not use home-made salt/sugar drinks as the quantity of salt and sugar has to be exact.
If your child vomits, wait 5-10 minutes and then start giving drinks again, but more slowly (for example, a spoonful every 2-3 minutes). Use of a syringe can help in younger children who may not be able to take sips.
Note: if you suspect that your child is dehydrated, or is becoming dehydrated, you should seek medical advice.
Fluids to treat dehydration
If your child is mildly dehydrated, this may be treated by giving them rehydration drinks. Your doctor or nurse will advise about how to make up the drinks and about how much to give. This can depend on the age and the weight of your child. If you are breast-feeding, you should continue with this during this time. Otherwise, don't give your child any other drinks unless the doctor or nurse has said that this is OK. It is important that your child should be rehydrated before they have any solid food.
Sometimes a child may need to be admitted to hospital for treatment if they are dehydrated. Treatment in hospital usually involves giving rehydration solution via a special tube called a 'nasogastric tube'. This tube passes through your child's nose, down their throat and directly into their stomach. An alternative treatment is with intravenous fluids (fluids given directly into a vein).
Eat as normally as possible once any dehydration has been treated
Correcting any dehydration is the first priority. However, if your child is not dehydrated (most cases), or once any dehydration has been corrected, then encourage your child to have their normal diet. Do not 'starve' a child with shigella infection. This used to be advised but is now known to be wrong. So:
- Breast-fed babies should continue to be breast-fed if they will take it. This will usually be in addition to extra rehydration drinks (described above).
- Bottle-fed babies should be fed with their normal full-strength feeds if they will take them. Again, this will usually be in addition to extra rehydration drinks (described above).
- Older children - offer them some food every now and then. However, if he or she does not want to eat, that is fine. Drinks are the most important, and food can wait until their appetite returns.
Other medication is not usually needed
You should not give medicines to stop diarrhoea to any child under 12 years old. They sound attractive remedies, but are unsafe to give to children due to possible serious complications. Also, children over 12 with shigella should not be given these medicines. This is because they may make symptoms worse. However, you can give paracetamol or ibuprofen to ease a high temperature or abdominal pains.
Probiotics are generally not recommended for children with gastroenteritis or food poisoning from any cause. This may change if further research shows that they are helpful.
What is the treatment of shigella in adults?
Antibiotics are used to treat shigella infection in adults. The usual antibiotic that is used is ciprofloxacin. However, the antibiotic may vary depending on advice that your doctor has received from the laboratory specialist who has performed tests on your stool sample.
Fluids - have lots to drink
The aim is to prevent dehydration, or to treat dehydration if it has developed. (Note: if you suspect that you are dehydrated, you should contact a doctor.)
- As a rough guide, drink at least 200 mls after each bout of diarrhoea (after each watery stool).
- This extra fluid is in addition to what you would normally drink. For example, an adult will normally drink about two litres a day, but more in hot countries. The above '200 mls after each bout of diarrhoea' is in addition to this usual amount that you would drink.
- If you vomit, wait 5-10 minutes and then start drinking again, but more slowly. For example, a sip every 2-3 minutes, but making sure that your total intake is as described above.
- You will need to drink even more if you are dehydrated. A doctor will advise on how much to drink if you are dehydrated.
For most adults, fluids drunk to keep hydrated should include water, fruit juice and soups. It is best not to have drinks that contain a lot of sugar, such as cola or pop, as they can sometimes make diarrhoea worse.
Rehydration drinks are recommended in people who are frail, or over the age of 60, or who have underlying health problems. They are made from sachets that you can buy from pharmacies. (The sachets are also available on prescription.) You add the contents of the sachet to water. Rehydration drinks provide a good balance of water, salts, and sugar. The small amount of sugar and salt helps the water to be absorbed better from the gut into the body. They do not stop or reduce diarrhoea. Do not use home-made salt/sugar drinks, as the quantity of salt and sugar has to be exact.
Eat as normally as possible
It used to be advised to 'starve' for a while if you had gastroenteritis. However, now it is advised to eat small, light meals if you can. Be guided by your appetite. You may not feel like food and most adults can do without food for a few days. Eat as soon as you are able but don't stop drinking. If you do feel like eating, avoid fatty, spicy or heavy food. Plain foods such as wholemeal bread and rice are good foods to try eating.
Antidiarrhoeal drugs should not be used if you have confirmed shigella infection or if you are passing blood and mucus in your stools. Paracetamol or ibuprofen are useful to ease a high temperature, headache or abdominal cramps.
Note: if you are receiving treatment for shigella infection and your condition is not improving within 48 hours, or if your condition worsens, you should contact your doctor or arrange for urgent medical review as needed. You should also urgently see a doctor:
- If you develop severe vomiting.
- If you are worried that you may be dehydrated, or are becoming dehydrated.
- If you have a persistent fever.
- If you develop abdominal distension.
- If you develop frank blood in your stools.
The same applies for your child.
Preventing the spread of shigella to others
If you or your child have shigella, the following are recommended to prevent the spread of infection to others:
- Wash your hands thoroughly after going to the toilet. Ideally, use liquid soap in warm running water, but any soap is better than none. Dry properly after washing. If your child wears nappies, be especially careful to wash your hands after changing nappies and before preparing, serving, or eating food.
- If a potty has to be used, wear gloves when you handle it, dispose of the contents into a toilet, then wash the potty with hot water and detergent and leave it to dry.
- Don't share towels and flannels.
- Don't prepare or serve food for others.
- If clothing or bedding is soiled, first remove any faeces into the toilet. Then wash in a separate wash at as high a temperature as possible.
- Regularly clean with disinfectant the toilets that you use. With hot water and detergent, wipe the flush handle, toilet seat, bathroom taps, surfaces and door handles at least once a day. Keep a cloth just for cleaning the toilet (or use a disposable one each time).
- Stay off work, school, college, etc, until at least 48 hours after the last episode of diarrhoea or vomiting. Avoid contact with other people as far as possible during this time.
- Food handlers: if you work with food and develop diarrhoea or vomiting, you must inform your employer and immediately leave the food-handling area. If shigella is confirmed, you should inform your employer and stay away from work until your doctor advises you when it is safe to return.
If you have shigella infection and you work with vulnerable groups of people such as the elderly, the unwell or the young, you should inform your employer. Your doctor also has the duty of reporting shigella infection to your local public health authority.
Are there any complications that can develop?
- Dehydration and salt (electrolyte) imbalance in your body. This is the most common complication. It occurs if the water and salts that are lost in your stools, or when you vomit, are not replaced by your drinking adequate fluids. If you can manage to drink plenty of fluids then dehydration is unlikely to occur, or is only likely to be mild, and will soon recover as you drink. Severe dehydration can lead to a drop in your blood pressure. This can cause reduced blood flow to your vital organs. If dehydration is not treated, kidney failure may also develop. Some people who become severely dehydrated need a 'drip' of fluid directly into a vein. This requires admission to hospital.
- Reactive complications. Rarely, other parts of your body can 'react' to shigella infection in your gut. This can cause symptoms such as arthritis (joint inflammation), skin inflammation and eye inflammation (either conjunctivitis or uveitis).
- Haemolytic uraemic syndrome. This is a serious condition where there is anaemia, a low platelet count in the blood, and kidney failure. It may be caused by toxins produced by some types of shigella bacteria. It is more common in children. If recognised and treated, most people recover well.
- Irritable bowel syndrome is sometimes triggered by shigella infection.
- Lactose intolerance can sometimes occur for a period of time after gastroenteritis caused by shigella. This is known as 'secondary' or 'acquired' lactose intolerance. Your intestine (gut) lining can be damaged by the episode of gastroenteritis. This leads to lack of an enzyme called lactase that is needed to help your body digest a sugar called lactose in milk. Lactose intolerance leads to bloating, abdominal pain, wind and watery stools after drinking milk. The condition gets better when the infection is over and the intestinal lining heals. It is more common in children.
- Reduced effectiveness of some drugs. During any episode of gastroenteritis, certain drugs that you may be taking for other conditions or reasons may not be as effective. This is because the diarrhoea and/or vomiting means that reduced amounts of the drugs are absorbed (taken up) into your body. Examples of such drugs are drugs for epilepsy, diabetes and contraception. Speak to your doctor or practice nurse if you are unsure of what to do if you are taking other drugs and have gastroenteritis.
Can shigella be prevented?
In general, good hygiene is essential to prevent the spread of many infections to others and to reduce your chance of picking up infections from others. Handwashing is the most important thing that you and your child can do. In particular, always wash your hands and dry them thoroughly, and teach children to wash and dry theirs:
- After going to the toilet (and after changing nappies or helping an older child to go to the toilet).
- Before preparing or touching food or drinks.
- Before eating.
If you smoke, you should also wash your hands before smoking. The simple measure of washing and drying hands regularly and properly is known to make a big difference to the chance of developing many infections.
In addition to this, when travelling to areas with poor sanitation, you should avoid eating or drinking the following to help reduce your chance of getting shigella infection. This is because shigella is often passed on by drinking contaminated water or eating food prepared using contaminated water. Avoid:
- Tap water
- Ice cream
- Ice cubes
- Raw or undercooked meat
- Fruit that has already been peeled
- Mayonnaise or sauces
Sealed bottled water, tea, coffee and alcohol are thought to be safe to drink.
Studies are underway throughout the world, looking at developing a vaccine that may be able to prevent shigella infection.
Further reading & references
- Diarrhoea and vomiting in children under 5, NICE Clinical Guideline (April 2009)
- Gastroenteritis, Clinical Knowledge Summaries (September 2009)
- Levine MM, Kotloff KL, Barry EM, et al; Clinical trials of Shigella vaccines: two steps forward and one step back on a long, hard road. Nat Rev Microbiol. 2007 Jul;5(7):540-53.
- Shigella. Accessed January 2010, Health Protection Agency
- The Second Infectious Intestinal Disease Study; Factsheet. Shigella. 11th January 2008.
- Kaminski RW, Oaks EV; Inactivated and subunit vaccines to prevent shigellosis. Expert Rev Vaccines. 2009 Dec;8(12):1693-704.
|Original Author: Dr Tim Kenny||Current Version: Dr Michelle Wright|
|Last Checked: 24/02/2010||Document ID: 12505 Version: 1||© EMIS|
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