Food poisonisng

 Food poisoning is suspected when there is a sudden onset of stomach cramps, vomiting and diarrhoea, following the consumption of food or drink, which may have been contaminated with viruses, bacteria or parasites.

 Food poisoning is most often suspected when large groups of people, who ate the same meal, fall ill simultaneously.

 When someone has eaten food contaminated with bacteria, the bacteria start to multiply in the stomach and bowels.

Vomiting and diarrhoea are the commonest symptoms of food poisoning, and are due either to the presence of a toxin or to the organism itself.

  Food poisoning can be fatal in certain cases, if appropriate treatment is not given immediately.

Bacterial contamination is most often the cause of food poisoning, followed by viruses and parasites.

 The severity of the symptoms experienced is usually closely related to the victim's age, medical history and general state of health.

 Basic health precautions can prevent the majority of food poisoning cases.

What is food poisoning?

Food poisoning is suspected when people fall ill (usually with nausea, vomiting and/or diarrhoea), following the consumption of the same food or drink which may have been contaminated with viruses, bacteria or parasites. In most cases, where there is bloody diarrhoea, the large intestine has been infected.

Food poisoning is most often suspected when large groups of people, who ate the same meal, fall ill simultaneously. The food may be contaminated with bacteria that have produced a toxin in the food, or else will produce a toxin in the body. Other types of bacteria multiply in the gut, and act directly on the gut to cause the symptoms.

The onset of these symptoms can be sudden, but can also take a few days, depending on the type of contamination involved, often complicating diagnosis. Food poisoning can be fatal in certain cases, if appropriate treatment is not given immediately.

There are more than 250 foodborne diseases, many of which cause other symptoms beside vomiting and diarrhoea. Bacterial contamination is most often the cause of food poisoning, followed by viruses and parasites. Chemicals and toxins can also cause food poisoning. In all of these cases of contamination, symptoms can manifest within a few hours or days, so diagnosis and identification of the source can sometimes be difficult. (Look under Cholera for waterborne infections and under Gastroenteritis for inflammation of the intestines often caused by Salmonella bacteria).

The similarity of the symptoms, which usually includes abdominal cramps, nausea, vomiting and diarrhoea, often complicates diagnosis. A thorough look at a patient's medical history and an investigation of recent foodstuffs consumed, will often assist the medical practitioner in making the correct diagnosis. It is important to do this, as different infections may require different treatments.

The severity of the symptoms experienced is usually closely related to the victim's age, medical history and general state of health. It can happen that two people who ingest the same infected foodstuff may be affected in very different ways. In severe cases of food poisoning, dehydration and kidney damage could occur.

What causes food poisoning?

The most common cause of food poisoning is bacteria, followed by viruses, parasites, chemicals and toxins.

Bacteria

Microbes, such as viruses and bacteria, that cause illness, are generally known as ‘germs’. These microbes can infect food or drink at any time from cultivation, to storage to preparation of the different foodstuffs. There are more than 20 organisms that can cause food poisoning. Of these, Campylobacter, Salmonella, E. coli, Staphylococcus aureus, Shigella, Clostridium perfringens, Botulism and Bacillus Cereus are encountered most frequently.

Several bacteria, such as certain strains of E. coli, Salmonella, Shigella and Campylobacter get into the lining of the intestine, causing secretion of fluid, and sometimes bleeding. The loss of fluid, if severe, and especially in the very young and very old, can be fatal.

Improper cooking, handling and storage of foods give bacteria an ideal opportunity to get into the food and to multiply. Bacteria are responsible for the vast majority of food poisoning cases. Bacteria multiply fast – all they need is warmth, moisture, food and time. Once inside the stomach, they have all four and continue to multiply at an alarming rate – given the right conditions one bacterium can multiply to 4 million in just eight hours.

Bacteria that cause food poisoning

Campylobacter. This is the most common cause of food poisoning. These bacteria are found in meat and undercooked poultry, untreated water and unpasteurised milk. Poultry and cattle faeces as well as pets with diarrhoea can be a source of these bacteria.

Thorough cooking of food and pasteurisation of milk will destroy campylobacter bacteria. It is also important to steer clear of having direct contact with animal wastes and to wash hands thoroughly after coming into contact with animals or animal wastes. The washing of hands before preparation of food and after handling of raw meat, is essential.

Abdominal cramping and pain, diarrhoea, which is sometimes bloody, nausea and vomiting, as well as fever are all symptoms of this kind of bacterial infection.

Usually no special treatment is needed. Usually people recover with no treatment in two to five days. Laboratory tests on the stool of an infected person will determine the presence of campylobacter bacteria. In severe cases, a health care professional can prescribe an antibiotic. It is very important to prevent dehydration in the case of patients who suffer from diarrhoea. Very few people die from a campylobacter infection.

Salmonella. Salmonella has been found in many different types of food, such as poultry and eggs, raw meat, and sometimes on unwashed vegetables or fruit, unpasteurised milk and other dairy products. It can also be spread by means of food that has been prepared on surfaces that previously contained raw meat, such as cutting boards. These bacteria are found in the gut and faeces of humans and animals. Salmonella survive refrigeration and are the second most common cause of food poisoning.

Proper cleaning of foodstuffs and cooking utensils and proper cooking of food will destroy salmonella. It is also important that people who have handled any foodstuffs that fall into the risk group mentioned above, wash their hands properly before continuing with food preparation.

The symptoms of salmonella poisoning are headaches, a fever, diarrhoea and abdominal cramps.

Cases of salmonella poisoning mostly clear up by themselves and do not require special treatment. It is nevertheless wise to consult a doctor if the diarrhoea becomes severe, as dehydration may result.

Typhoid is caused by one of the salmonella bacteria and is a more serious infection than the other salmonella infections and requires antibiotic treatment. (See the article on typhoid fever)

E. coli. The full name of this bacterium is Escherichia coli (E. coli). Both harmless and disease-causing strains of this organism are found in the intestinal tracts of animals and humans. It thrives in raw or undercooked meat (especially beef products), unpasteurised milk dairy products and has also been found in raw vegetables and apple juice. It is also very often called 'the traveller's bug' - it often affects people who are visiting foreign countries, as it also found in untreated water. Swimming in water that is sewage-infected could also result in an E. coli infection.

There is a particular strain of E. coli that is called enterohaemorrhagic E. coli or EHEC, which can lead to bloody diarrhoea and kidney failure in children. It is also dangerous to people whose immune-systems are compromised in some way.

The E. coli bacteria will be destroyed if beef products are properly cooked. Fruit and vegetables must be properly washed before eating and travellers must only drink bottled water when in a country where the cleanliness of the tap water is questionable. It is best not to swim in rivers in these countries and people should stay away from underchlorinated swimming pools.

The symptoms of E. coli are similar to the symptoms of other bacterial infections, and include exhaustion, occasional vomiting, watery and sometimes bloody diarrhoea, abdominal cramps and severe nausea.

In most cases, treatment is not needed. The infection usually clears up within five to ten days by itself. Health care professionals advise against the taking of diarrhoea medication. Although the symptoms will often resolve spontaneously, taking antibiotics may reduce the symptoms slightly. If you are on holiday, this could be quite important.

Staphylococcus aureus. These bacteria are present on the human skin, in cuts on the skin, in people's noses and in boils. It is also found in unpasteurised milk. It contaminates food via droplets from the nose, or through touch by unwashed hands. People who have boils or impetigo should not prepare food for others until the infection has cleared.

The danger of these bacteria, is that they could survive both refrigeration and the cooking process. These bacteria, though they can survive the refrigeration process, do not multiply at such low temperatures. They are usually destroyed by pasteurisation and cooking, but not always. These bacteria are often found in cooked meats, in poultry, both cooked and undercooked, and in many different types of foods which are prepared, but not cooked immediately. They are especially fond of creamy, dairy foods (such as potato salads). Foods left at room temperatures provide ideal breeding grounds for this type of bacteria. The organism produces toxin while the food is cooling down, and the ingestion of this toxin is what causes the symptoms. Since the toxin is already present, symptoms usually start very quickly.

A person who has been infected with staphylococcus aureus, usually starts vomiting between two to six hours after ingestion. Vomiting is severe, as are abdominal pains. Sometimes headaches and fevers are also symptoms. Dehydration and loss of electrolytes could also be severe. Symptoms usually do not last long and can be over in as little as twelve hours.

Treatment usually consists of giving the patient adequate fluids, and administering fluids and electrolytes intravenously, if needed. Fatalities usually only occur in the very young, the very old or in people whose health is compromised by some other condition.

Clostridium perfringens. This type of bacteria can be found in a wide range of animal faeces. It is found in soil, in raw meat and poultry, animal wastes and sewage.

The spores of this organism are very tough, and survive for ages in the environment. The spores can contaminate food if food handling is improper, and the spores of these bacteria are not always killed during the cooking process. It is particularly associated with foods such as gravies, stews, pies, and cooked meat dishes, such as large joints of meat and poultry.

When food is either cooked slowly, or only partially reheated, the spores can germinate and reproduce rapidly. Pies, which are often kept at moderate heat for hours on end before being sold, are often a source of this type of bacteria. Once the bacteria are ingested, they produce a toxin in the gut, which causes the symptoms - predominantly diarrhoea and cramps.

Botulism. The bacterium Clostridium botulinum produces a nerve toxin which causes this relatively rare, but serious, paralytic illness. Foodborne botulism can be fatal and its danger lies in the fact that many people can be infected by eating the same contaminated food. Infant botulism is caused when the spores of the bacteria grow in the intestines and release toxin.

Botulism is most often found in home-canned foods, which have a low acid content. It is also found in fermented fish, and potatoes baked in tin foil, which are not immediately eaten or refrigerated. The spores germinate in certain foods under the right conditions, and then from the toxin. High temperatures destroy the botulism toxin, so it might be advisable to boil home-canned foods for ten minutes before eating them.

The bacterial toxin brings about muscle paralysis, which can cause slurred speech, drooping eyelids, double vision and general muscle weakness. It is a difficult condition to treat, as the muscle paralysis makes it difficult to diagnose. It is a very serious condition, which can be fatal, as it causes respiratory failure in serious cases and can result in someone being put on a respirator. If diagnosed early, foodborne botulism can be treated with an antitoxin, but recovery still takes several weeks.

Bacillus cereus. These bacteria are found in dust and soil, as well as in an astonishingly wide range of foodstuffs. These range from pasta and rice dishes to meat and vegetable dishes, soups, dairy products, sauces and pastries.

These bacteria flourish in all these foods when they are not refrigerated after cooking. The spores of Bacillus Cereus are not easily destroyed by heat and will often survive the cooking and the reheating of food. They germinate when the food is allowed to cool slowly, and can produce two types of toxin. One type of toxin is similar to the toxin of Staph aureus, is produced in the food, and causes severe vomiting. The other toxin is produced by the organisms when they reach the gut, and cause a more predominantly diarrhoeal illness.

Symptoms of this type of food poisoning can take anything from one to five days to develop. Severe diarrhoea, which may be bloody, is a symptom of this type of poisoning. In extremely severe cases, infection may lead to kidney failure in young children, and even death.

Shigella. The Shigella bacteria is spread by people infected with Shigella who prepare food with hands that were not properly washed after a visit to the toilet. It can also be spread when people eat food contaminated by flies bred in infected faeces. Swimming in or drinking infected water can also lead to contamination, as can eating vegetables grown in fields where there was sewage present.

It is often found where people live in crowded and unhygienic conditions and sometimes spreads quickly through whole institutions where hygiene may be inadequate. These bacteria spread extremely easily and can infect large numbers of people in a short space of time.

To prevent shigellosis, the washing of hands after going to the toilet or changing nappies is essential. Hands should always be washed before preparing any food or drinks.

The symptoms include nausea, vomiting, watery and sometimes bloody diarrhoea and abdominal pain.

Usually this infection clears up by itself, but sometimes antibiotics are prescribed. Again, anti-diarrhoea medication is not advised.

Chemicals

Chemicals can also be responsible for food poisoning. The ingestion of certain plants like poisonous mushrooms, potatoes that have gone green, the oleander bush, or foodstuffs that have been excessively sprayed with insecticides can be the source of food poisoning in humans. The ingestion of an animal that contains poison, such as shellfish exposed to red tide, can also lead to food poisoning.

The symptoms of chemical poisoning vary according to the poison that has been ingested. Symptoms can include dizziness, tearing, vomiting, diarrhoea, salivation, sweating, stomach cramps, occasional convulsions, constriction of the pupils, muscle weakness and breathing difficulty. These symptoms can manifest from a few minutes after ingestion of the poison, to a couple of hours, or even days. Chemical poisoning can be fatal and should be treated as a medical emergency.

Medical staff may attempt to remove the toxin either by gastric lavage (stomach pump), or by administering ipecac syrup to induce vomiting, or laxatives to empty the intestine. Intravenous fluids may be necessary if a patient is dehydrated, pain medication may be necessary, and in the case of respiratory failure, a ventilator.

Parasites

Two parasites that can commonly be spread by contaminated water are called Giardia Lamblia and Cryptosporidium and are spread when drinking water is infested with these parasites. Healthy people will mostly recover, but they can be fatal to people whose immunity is compromised in some way.

Signs and symptoms of food poisoning

These vary tremendously depending on which kind of bacteria, virus, parasite or chemical someone has ingested.

General symptoms of food poisoning usually include stomach cramps, vomiting, diarrhoea and fever. For specific symptoms of the main types of bacterial poisoning, see separate listings above. If food poisoning is suspected, it is always better to err on the side of caution, and seek medical treatment, especially if the source of contamination is unknown.

Diagnosis of food poisoning

Identifying the specific source of contamination is not always easy, as several days may have passed between ingestion of the contaminated food and a patient's arrival at a hospital or treatment centre.

Doctors will question a patient closely as to what they have eaten in the preceding days to try and determine what type of infection they are dealing with. Symptoms of different kinds of food poisoning are not dissimilar from each other, complicating diagnosis. They mostly include stomach cramps, diarrhoea, vomiting and often fever.

Blood tests and stool analysis can sometimes be done to get conclusive results.

Treatment of food poisoning

While most types of food poisoning will clear up without treatment within a few days, it is important to seek medical help in the following cases:

  If the source of the contamination is unknown

   If the person has eaten mushrooms or seafood

   If the person develops bloody diarrhoea

  If the person develops breathing problems

  If the vomiting and diarrhoea still persist after 48 hours

  If it is an infant or elderly person

 If the person's immunity is compromised by some other infectious disease

  If the person develops a fever

In cases of ingestion of certain chemicals, medical staff will attempt to remove the toxin from the intestinal tract, either by means of gastric lavage (stomach pump), medication to induce vomiting or laxatives to induce diarrhoea.

Rehydration of a patient is important and is usually done by administering fluids and electrolytes intravenously. Antibiotics are sometimes given if there are signs of infection in the intestinal tract. In certain cases anti-diarrhoeal medication is prescribed, but this is generally not advised in bacterial infections.

In serious cases of chemical poisoning, which may result in respiratory failure, patients may need to be ventilated. If the toxin has been identified, there are antitoxins available in some cases. Food poisoning is a condition which needs to be taken seriously as it could be fatal.

Prevention of food poisoning

There is much that can be done to prevent food poisoning:

 Never drink water that may be contaminated. Boil drinking water first if you are unsure about whether it is safe to drink. Also do not swallow swimming pool water.

Wash hands regularly. This is the most important preventative measure. Hands should be washed after you have been to the toilet, before and after food preparation and after you have touched raw meat, fish or poultry.

 Try and avoid coming into contact with any animal faeces. If you should, wash your hands carefully with anti-bacterial soap.

Cooking utensils and cutting boards should be kept clean by being washed with hot soapy water on a regular basis. Do not reuse utensils that have touched raw meat, fish or chicken. Put kitchen cloths and sponges in the microwave for 60 seconds as this will kill all bacteria present in them.

 All fruit and vegetables should be washed properly before eating.

All food, especially meat, should be cooked thoroughly. Undercooked poultry is a great source of bacteria.

 Food should either be kept hot or cold. After two hours at room temperature, bacteria start multiplying in foodstuffs. Refrigerate leftovers immediately. Throw out any old food in the fridge.

 Once food has thawed, it should not be refrozen.

  Never eat anything from bulging or dented cans.

 Don't eat anything that has passed its expiry date. Don't eat, or even taste anything, that looks suspect. Get into a habit of always checking these dates when buying food.

 Steer clear of home-bottled preservatives.

 Don't eat wild mushrooms, unless you really know which ones are dangerous and which are safe.

  Steer clear of seafood that does not come from a reputable source.