Dysentery: Causes, Symptoms and Treatments
Dysentery is an intestinal inflammation, especially in the colon, that can lead to severe diarrhea with mucus or blood in the feces.
Patients typically experience mild to severe abdominal pain or stomach cramps. In some cases, untreated dysentery can be life-threatening, especially if the infected person cannot replace lost fluids fast enough.
When people in industrialized nations have dysentery, signs and symptoms tend to be mild. Many won’t even see their doctor, and the problem resolves in a few days. Even so, if a doctor in Western Europe, North America and many other countries comes across a case of dysentery, local authorities need to be told – it is a notifiable disease.
The World Health Organization1 says there are two main types of dysentery:
- Bacillary dysentery, caused by Shigella, a bacterium. In Western Europe and the USA it is the most common type of dysentery among people who have not recently been to the tropics.
- Amoebic dysentery (amoebiasis) This is caused by Entamoeba histolytica, a type of amoeba, and is more common in the tropics. An amoeba is a protozoan (single-celled) organism that constantly changes shape.
The World Health Organization estimates that shigellosis accounts for about 120 million cases of severe dysentery2 with blood and mucus in stools worldwide. The vast majority of cases occur in developing nations among children aged less than five years.
Approximately 1.1 million people are thought to die from Shigella infection globally each year. Sixty percent of these deaths are among very young children.
Causes of dysentery
Sir Francis Drake died of dysentery in 1596 while attacking San Juan, Puerto Rico
Dysentery is mainly caused by a bacterial or protozoan (one cell organism, such as an amoeba) infection. It can also be caused by a parasitic worm infestation. More rarely, a chemical irritant or viral infection can also be a cause.
Causes of bacillary dysentery
An infection with a bacillus of the Shigella group is the most common type of dysentery. According to the National Health Service (NHS), UK, Shigella sonnei is the most common, followed by Shigella flexneri, Shigella boydii and Shigella dysenteriae, the last one listed produces the most severe symptoms.
Poor hygiene is the main cause of bacillary dysentery infection. However, it can also spread because of tainted food.
Causes of amoebic dysentery
Amoebic dysentery is usually caused by infection with the Entamoeba histolytica amoeba.
Amoebic dysentery is more common in the tropics while bacillary dysentery is more common elsewhere. However, parts of rural Canada do get reports of amoebic dysentery.
The amoeba group together and form a cyst, the cysts come out of the body in human feces. In areas of poor sanitation, these cysts (which can survive for a long time), can contaminate food and water, and infect other humans. The cysts can also linger in infected people’s hands after going to the toilet. Good hygiene practice reduces the risk of infecting other people.
Symptoms of dysentery
A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor notice. For example, pain may be a symptom while a rash may be a sign.
Abdominal pain, diarrhea and fatigue are possible symptoms of dysentery.
In developed countries signs and symptoms of dysentery tend to be much milder than in developing nations or tropical areas. Patients with mild symptoms will have a slight stomach ache (cramping), and will frequently go to the toilet because of diarrhea.
Symptoms usually appear from one to three days after the person has become infected – this is called the incubation period. In most cases the patient recovers completely within a week. How often the individual goes to the toilet and has mucus or blood in feces usually depend on what is causing the disease.
In some cases people who get dysentery also develop lactose intolerance, which can take a long time to go away, sometimes even years.
Symptoms of amoebic dysentery include:
- abdominal pain
- fever and chills
- nausea and vomiting
- watery diarrhea, which can contain blood, mucus or pus
- painful passing of stools
- intermittent constipation.
The amoeba can tunnel through the intestinal wall and spread into the bloodstream and infect other organs; ulcers can develop, these ulcers may bleed, causing blood in stools.
In some cases symptoms may persist for several weeks, but usually only last a few days. The amoebas may continue living within the host (the human) even after symptoms have gone, increasing the likelihood of a recurrence when the person’s defenses are down. The amoebas are less likely to survive if the patient receives treatment.
Signs and symptoms of bacillary dysentery – as in other types, symptoms tend to appear from one to three days after the person has been infected. Most typically, there is just mild stomachache and diarrhea, and no blood or mucus in the feces. For many, symptoms are so mild they do not even bother going to the doctor, and the problem resolves in a few days. Initially, the infected person goes to the toilet frequently with diarrhea.
Although much less common, some people with bacillary dysentery may have blood or mucus in their feces, abdominal pain may be intense, there may be an elevated body temperature (fever), nausea and vomiting.
On the next page we look at how dysentery is diagnosed, plus the treatment options and how dysentery can be prevented.
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Diagnosis of dysentery
The doctor, initially usually a GP (general practitioner, primary care physician) will ask the patient about symptoms and carry out a physical examination. A stool sample may be ordered, especially if the patient has been abroad in the tropics.
In rare cases, if symptoms are severe, other diagnostic tests may be recommended, such as an ultrasound scan or an endoscopy.
Treatments for dysentery
Rehydration therapy – initially this is done using oral rehydration; the patient is encouraged to drink plenty of liquids. Diarrhea, as well as vomiting results in loss of fluids that have to be replaced to prevent dehydration. If the diarrhea and/or vomiting is profuse the medical team may recommend intravenous fluid replacement – the patient will be on a drip.
Antibiotics and amoebicidal drugs – experts say that if possible, the administration of medications to kill the cause of the dysentery should be held back until lab tests determine whether the illness is being caused by a bacterium or amoeba. If this is not possible, depending on the severity of symptoms, the patient may be given a combinations of antibiotic and amoebicidal medication.
If symptoms are not severe and the doctor determines it is Bacillary dysentery (Shigella), the patient most likely will receive no medication – in the vast majority of cases the illness will resolve within a week. Oral rehydration is important.
If amoebic dysentery is diagnosed the patient will probably start with a 10-day course of an antimicrobial medication, such as Flagyl (metronidazole). Diloxanide furoate, paromomycin (Humatin), or iodoquinol (Yodoxin) may also be prescribed to make sure the amoeba does not survive inside the body after symptoms have gone.
Antirheumatic drug Ridaura (auranofin) may offer a cheap, low-dose treatment for the amoebic infections that cause dysentery in humans globally. The drug has only been tested in the laboratory and in animal studies, researchers from the University of California in San Diego and the University of California in San Francisco reported in Nature Medicine (May 2012 issue).
Prof. James McKerrow and team had been screening already approved medications to see whether any of them could be used in the developing world when they made their discovery.
Prof McKerrow said “When we’re looking for new treatments for the developing world, we start with drugs that have already been approved.”
They found that auranofin, which is already FDA-approved for the treatment of arthritis, was ten times more potent than metronidazole against the parasite Entamoeba histolytica.
According to the researchers, the combination of an off-patent medication plus many years of clinical safety data means we may well have a worldwide lower-cost solution, with fewer side effects or risk of drug resistance than the therapies currently available.
Complications of dysentery
Dehydration – diarrhea and vomiting can quickly lead to dehydration. This can happen especially quickly with infants and young children. Dehydration can be life-threatening.
Liver abscess – if the amoeba spreads to the liver.
Prevention of dysentery
In most cases, dysentery is caused by poor hygiene. Individuals can take measures to reduce their risk of infection by regularly washing their hands, especially before and after going to the toilet and preparing food.
If you are in an area where the risk of dysentery is higher, only drink water from reliable sources (bottled water). If you drink from the bottle, make sure it is opened in front of you and clean the top of the rim. Make sure the food you eat is thoroughly cooked and beware of ice cubes; you may not know what type of water was used to make them. Use purified water to clean your teeth.