Shigella is a group of germs that can cause gastroenteritis with dysentery. Dysentery is the name used when diarrhoea is accompanied by blood and mucus.
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. 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. One group of people found to be at risk of shigella are men who have sex with men when contact with the back passage (anus) is involved.
What are the symptoms of shigella?
Some people with shigella infection actually have no symptoms. However, the germs (bacteria) will still be present in their stools (faeces) and they can still pass on the infection to other people.
But most people with shigella infection develop symptoms. Symptoms tend to come on within one to seven days of contact with the bacteria (for example, 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 tummy (abdominal) cramps.
- High temperature (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 lack of fluid in the body (dehydration). 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.
How is shigella diagnosed?
Shigella infection is usually diagnosed after a sample of your stools (faeces) is sent to the laboratory for testing. If you have a gastroenteritis infection with blood and mucus in your diarrhoea, you should see a doctor who can arrange for a sample of your stools to be tested.
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What is the treatment of shigella in children?
Symptoms often settle within a few days or so as a child's immune system is usually able to clear the infection. Children can usually be treated at home. Occasionally, admission to hospital is needed if symptoms are severe or if complications such as severe dehydration develop.
Introduce food once any dehydration has been treated.
Medication is not usually needed
You should not give medicines to stop diarrhoea to children under 12 years old. They sound attractive remedies but are unsafe to give to children, due to possible serious complications. Also in shigella, they may make the condition worse. However, you can give paracetamol or ibuprofen to ease a high temperature (fever) or headache.
If symptoms are severe or persist for several days or more, or there is blood in the stools (faeces), a doctor may ask for a sample of the diarrhoea. If shigella is confirmed, in some cases an antibiotic medication may be needed. Your child is likely to need an antibiotic if there is blood in their diarrhoea. An antibiotic may also be prescribed if your child has a condition where their immune system is not working as well as normal - for example due to chemotherapy or an illness such as AIDS
What is the treatment of shigella in adults?
Symptoms often settle within a few days or so as your immune system usually clears the infection. Occasionally, admission to hospital is needed if symptoms are severe, or if complications develop (see below).
You should follow the advice about food and liquid given for all causes of traveller's diarrhoea.
.A course of antibiotic medicine is sometimes needed. You may need antibiotics if your symptoms are severe, or if you have blood in your diarrhoea. You may also need antibiotics if you have a condition where the immune system is not working as well as normal - for example, due to chemotherapy or an illness such as AIDS. Where an antibiotic is needed, usually one called ciprofloxacin is used.
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 sickness (vomiting).
- If you are worried that you may be dehydrated, or are becoming dehydrated.
- If you have a persistent high temperature (fever).
- If you develop abdominal swelling (distension).
- If you develop blood in your stools.
The same applies for your child.
Are there any complications that can develop?
Complications are similar to those for other causes of traveller's diarrhoea.
Reporting the food poisoning episode
Any suspected case of food poisoning from eating takeaway or restaurant food should be reported to the local Environmental Health Office. This is so that the business can be investigated by environmental health officers. Further actions may be taken if there is a problem with their food hygiene practices. It is hoped that this will help to reduce the chance that other people will get food poisoning. You can find your local food standards enforcer from the Food Standards Agency's 'Report a food problem' service. If your doctor suspects or confirms that your child has food poisoning, they are also required by law to report this.
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. Hand washing is the most important thing that you and your child can do. You should also take the same precautions regarding food and drink as other causes of traveller's diarrhoea.
Men who have sex with men should wash their hands after touching a partner's back passage (anus) or coming into contact with a condom used during anal sex. Condoms should be changed between anal sex and oral sex. Mouth to anus contact (also known as 'rimming') is very high-risk and should be avoided.
Studies are underway throughout the world, looking at developing a vaccine that may be able to prevent shigella infection.
Further reading and references
Acute diarrhoea in children: racecadotril as an adjunct to oral rehydration; NICE Evidence summary, March 2013
Bourgeois AL, Wierzba TF, Walker RI; Status of vaccine research and development for enterotoxigenic Escherichia coli. Vaccine. 2016 Mar 15. pii: S0264-410X(16)00287-5. doi: 10.1016/j.vaccine.2016.02.076.
Travellers' diarrhoea; Fitfortravel
Riddle MS, Connor BA, Beeching NJ, et al; Guidelines for the prevention and treatment of travelers' diarrhea: a graded expert panel report. J Travel Med. 2017 Apr 124(suppl_1):S57-S74. doi: 10.1093/jtm/tax026.
Giddings SL, Stevens AM, Leung DT; Traveler's Diarrhea. Med Clin North Am. 2016 Mar100(2):317-30. doi: 10.1016/j.mcna.2015.08.017.