Diarrhoea

Diarrhoea can be acute or chronic and can have a wide range of causes, including infectious diseases. Viral, bacterial, and parasitic infections can cause diarrhoea that lasts several days to a few weeks. Sometimes the symptoms may linger, causing chronic diarrhoea , particularly in those with suppressed immune systems (such as those with HIV/AIDS, cancer or organ transplantation). The person experiencing the diarrhoea is likely to be infectious to others. The virus, bacteria, or parasite is shed into the stool and can therefore be passed from person to person. Inadequately treated sewage can result in food or drinking water that are contaminated with faecal matter and thus diarrhoeal diseases. Also people in close contact with someone with diarrhoea can pick it up through contaminated hands or surfaces.

Once a person is infected, they may then pass the infection on to others around them unless careful hygiene practices (especially thorough hand washing) are followed. This route for the spread of infection presents a challenge in households with infected infants, in day care centres and in nursing homes. Sometimes an outbreak of bacterial or parasitic infection can be traced back to a particular restaurant or a single food item.

Some viral, bacterial and parasitic infections which cause diarrhoea are more common in low income countries with a tropical climate. So, visitors can be at risk of exposure when traveling for work or on holiday. Things as simple as contaminated ice cubes, a fresh fruit salad, or food from an open market can cause illness.

Common causes of acute diarrhoea:

Parasites: The most common faecal parasites in the UK are Giardia (Giardia duodenalis) Entamoeba (Entamoeba histolytica) and Cryptosporidium (Cryptosporidium parvum/ Cryptosporidium hominis). These single cell parasites are found in mountain streams and lakes throughout the world and may infect swimming pools and occasionally public water supplies. Other more worm-like parasites, such as roundworms or tapeworms, may also occasionally cause infections.

In other parts of the world, especially in low income countries and in warm climates, a much wider range of parasites may be encountered. These parasites include flat worms, roundworms, hookworms and flukes. Visitors usually become infected by eating or drinking something that has been contaminated with the parasite but some infectious agents can get into people through the skin.

Viruses: Rotavirus is a common cause of severe diarrhoea among young children and the elderly. Although there is a vaccine against rotavirus offered to children, it is still the leading cause of death from diarrhoea world wide. Outbreaks of diarrhoeal illness in hospitals, care homes and on cruise ships are often caused by norovirus.

Bacteria: Bacteria can cause diarrhoea in three different ways, depending on the type of organism. Some bacteria grow in the body causing illness themselves, some produce a toxin while in the body and others grow in contaminated food and produce a toxin which people may then consume

Bacteria that can infect the gastrointestinal tract include:

• Salmonella, often found in raw eggs and poultry and may be carried by reptiles kept as pets
• Campylobacter, from raw or undercooked poultry.
• Vibrio cholerae which causes cholera

Bacteria that produce a toxin in infected food that can persist after cooking include:

• Staphylococcus aureus
• Bacillus cereus

Bacteria from food that produce a toxin after multiplying in the gastrointestinal tract include: Shigella, which causes dysentery and can be picked up from food and water contaminated with faeces, particularly in tropical countries

• Types of Escherichia coli such as E.coli 0157:H7 . This is commonly associated with raw or undercooked beef, but also with a wide variety of prepared foods. Hamburgers made at home and inadequate hand washing by food preparers have been shown to be particular risk factors. After an incubation period of 1 to 10 days it causes diarrhoea which contains blood in over 70% of cases. This bacterium can to lead to red blood cell destruction and kidney failure (the haemolytic uraemic syndrome).

Acute diarrhoea may also be due to treatment with broad-spectrum antibiotics, or to other medications that cause diarrhoea as a side effect. Antibiotic treatment can decrease the normal flora which are the “good” bacteria that live in the gastrointestinal tract, help digest our food, and provide a protective barrier against the “bad” bacteria (pathogens). When the growth of the normal flora is prevented , it is easier for a pathogen to grow and multiply. Toxins produced by the bacterium Clostridium difficile are often the culprit in antibiotic related diarrhoea.

Common causes of chronic diarrhoea:

Chronic diarrhoea (diarrhoea that lasts for more than a few weeks), sporadic diarrhoea, and diarrhoea that alternates with constipation are most frequently associated with non-infectious causes. These may include:

• Inflammatory bowel conditions such as Crohn’s disease
• Bowel dysfunction as seen in the irritable bowel syndrome (IBS)
• Malabsorption diseases such as cystic fibrosis
• Stomach or gallbladder surgery (the rate at which the food travels through the digestive tract may change)
• Food intolerance such as lactose intolerance or coeliac disease
• Chemotherapy or radiotherapy affecting gastrointestinal tract
• Endocrine problems such as diabetes and thyroid disease
• Bowel cancer and polyps
• Self-induced with laxatives
• Psychological causes such as stress

Your doctor will want to ask you about your diarrhoea. The frequency, quantity, and consistency of normal bowel movements are very individual. They depend on your metabolism, the foods you eat, your activity level, the amount of fluids you drink, the medicines you take, and even any stress that you are experiencing. Your doctor will be looking for changes from your normal bowel habits. The doctor will look for alterations that are commonly associated with diarrhoea-causing conditions. Your doctor will be asking you a series of questions that help choose which laboratory tests will be the most useful. These questions may include:

• What is the frequency of your stools?
• How long you have been experiencing diarrhoea?
• What are the consistency, colour, and approximate volume of the stools?
• Is there blood or mucus in the stool?
• What other symptoms are you having: abdominal pain, nausea, fever, headache, fatigue?
• What and where have you eaten recently?
• Have you travelled outside the UK recently?
• Are any of your family members, close acquaintances or co-workers ill?
• Have you been on antibiotics lately?
• If your diarrhoea is persistent or alternates with constipation, have you had any unexpected weight loss?

Laboratory Tests
If your diarrhoea is uncomplicated and goes away within a few days, your doctor may not search for the cause of your gastrointestinal upset. He/she may request one or more of the following tests if your diarrhoea is severe, if there is blood or mucus present or if it is continues for sometime. This is especially true if you have been abroad or have eaten or drunk anything that has also made someone close to you ill.

Tests to identify diarrhoea caused by infection include:

• Ova and parasite (OCP) examination. A microscopic examination of your stool for parasites and the ova (eggs, cysts) of parasites.
• Rapid, 'point of care', lateral flow tests for Giardia, Cryptosporidium and E. histolytica 
• Stool white blood cells. These may be present in the stool when there is a bacterial infection.
• Stool culture to check for diarrhoea-causing  bacteria
• Antibody tests for parasites. These are not as useful to detect current infections but may be requested to check for past or chronic infections, especially if unusual parasitic infections are suspected.
• Multiplex PCR to look for viruses such as norovirus and rotavirus. These tests are often to set up for common diarrhoeal bacteria and parasites as well in a single test.
• Rapid, 'point of care', lateral flow test for norovirus.
• Clostridium difficile toxin,a rapid test used to identify a Clostridium difficile infection by detecting the toxin made by the bacteria.
• Electrolytes including sodium, potassium and urea. If you are dehydrated your doctor may want to do a blood test to determine whether your electrolytes have become imbalanced.
• Biopsy of the small intestine is rarely done to look for signs of parasitic infection

Non-Laboratory Tests
Endoscopy, sigmoidoscopy or colonoscopy are used to look at portions of the gastrointestinal tract.

The best ways to prevent a bacterial, parasitic, or viral gastrointestinal infection are not to drink water or eat food that may be contaminated and to be careful with hygiene measures, such as hand washing. Food that might be contaminated, such as raw meats and eggs, should be cooked thoroughly. Cooked foods and foods that are served raw should not touch any surfaces that may have been contaminated.

If someone in your household has a diarrhoeal infection, careful hand washing by all family members is recommended. It is best if the infected person does not prepare food or drink for others until the infection is over.

When you are travelling in developing countries it is best to drink only boiled or bottled water, carbonated drinks, and hot cooked foods. Avoid fresh fruits and vegetables, limiting yourself to those that you can peel yourself. Food from street food stores is generally not considered safe.

Laboratory confirmation of the cause of diarrhoea can be important for monitoring cases (for example in people who have travelled abroad) and during outbreaks. Each country of the UK has its own centre for reporting infectious diseases, although the UK Health Security Agency does some coordination of information. Other than in travel related cases, public health officials will want to try to determine where your infection came from so that they can address any potential concerns. For instance, if your infection is due to contaminated food served at a restaurant or to a contaminated public water supply, steps will need to be taken to prevent the spread of the infection.

If your diarrhoea is uncomplicated and goes away within a few days, your doctor is unlikely to prescribe any treatment for your gastrointestinal (GI) upset. In healthy people, most bacterial infections of the GI tract resolve by themselves. In some cases, antibiotics actually prolong the infection and may lead to carrying the organisms for months (carrier state). Patients with underlying diseases that impair the immune response, such as cancer or HIV, may be treated with antibiotics since they cannot clear the infection on their own. If the diarrhoea is severe, bloody, includes mucus and/or has lasted for more than three or four days, then your doctor will often request tests to identify the cause of your diarrhoea and treat it accordingly. This is especially true if you have been abroad or if family members, close acquaintances or work colleagues are also ill.

For viral infections and many pathogenic bacterial infections, the main treatment is to make sure that the patient replaces lost fluids and electrolytes. Infants and those with severe dehydration may not be able to drink enough to rehydrate themselves and may have to be taken into hospital for a short period of time. Your doctor will monitor your health, give you advice on preventing the spread of the infection, and watch for any complications.

Most parasitic infections are treated with medicine, although some may resolve on their own. With some bacterial and parasitic infections, your doctor may treat the entire family even if only one member is obviously affected. There is currently no effective treatment for Cryptosporidium. Most people with healthy immune systems will get rid of this infection, but some with poor immune systems (such as those with HIV/AIDS or organ transplantation) may develop a chronic infection.

Talk to your pharmacist before taking an over-the-counter anti-diarrhoea medicine. They relieve symptoms of acute (severe) diarrhoea and can be useful to reduce discomfort and social disruption. Do not take them if there is blood in your stool or you have a raised temperature. Never give anti-diarrhoea medicines to a child. Diarrhoea is one of the methods your body uses to help get rid of the infection. If you slow down or prevent this from happening by taking an anti-diarrhoea medicine you can prolong the time that you are ill.

For diarrhoea caused by a food intolerance such as lactose intolerance, treatment involves avoidance of the cause. A diagnosis of coeliac disease requires avoidance of foods containing gluten.