| Foodborne illness or food poisoning is caused by consuming food contaminated with pathogenic bacteria, toxins, viruses, prions or parasites.
Such contamination usually arises from improper handling, preparation or storage of food. Foodborne illness can also be caused by
adding pesticides or medicines to
food, or by accidentally consuming naturally poisonous substances like poisonous mushrooms or reef fish. Contact between food and pests, especially flies, rodents and cockroaches, is a further cause of
contamination of food.
Some common diseases are occasionally foodborne mainly through the water vector, even though they are usually transmitted by other routes. These include infections caused by
Shigella, Hepatitis A, and the
parasites Giardia lamblia and Cryptosporidium parvum.
World Health Organisation definition
Foodborne illnesses are defined by the World Health Organization as diseases, usually either infectious or toxic in nature, caused by
agents that enter the body through the ingestion of food. Every person is at risk of foodborne illness[1] (http://www.who.int/mediacentre/factsheets/fs237/en/).
Statistics
There are every year about 76 million foodborne illnesses in the United
States (i.e. 26,000 cases for 100,000 inhabitants), 2 million in the United Kingdom (3,400 cases for 100,000 inhabitants) and 750,000 in France (1,210 cases for 100,000 inhabitants).
In the United States
In the United States, for 76 million foodborne illnesses (26,000 cases for 100,000 inhab.):
- 325,000 were hospitalised (111 per 100,000 inhab.);
- 5,000 people died (1.7 per 100,000 inhab.).
Source:
In France
In France, for 750,000 cases (1,210 per 100,000 inhab.):
- 70,000 people consulted in the emergency department of an hospital (113 per 100,000 inhab.);
- 113,000 people were hospitalised (24 per 100,000 inhab.);
- 400 people died (0.1 per 100,000 inhab.).
The causes of the illness (toxic factor) are:
Causes of foodborne illness in France
|
Cause |
cases per year |
| 1 |
salmonella |
~8,000 cases (13 per 100,000 inhab.) |
| 2 |
campylobacter |
~3,000 cases (4.8 per 100,000 inhab.) |
| 3 |
parasite
incl. toxoplasma |
~500 cases (0.8 per 100,000 inhab.)
~400 cases (0.65 per 100,000 inhab.) |
| 4 |
listeria |
~300 cases (0.5 per 100,000 inhab.) |
| 5 |
hepatitis A |
~60 cases (0.1 per 100,000 inhab.) |
The causes of death by foodborne illness are:
Causes of death by foodborne illness in France
|
Cause |
cases per year |
| 1 |
salmonella |
~300 cases (0.5 per 100,000 inhab.) |
| 2 |
listeria |
~80 cases (0.13 per 100,000 inhab.) |
| 3 |
parasite |
~37 cases (0.06 per 100,000 inhab.)
(toxoplasma in 95% of the cases) |
| 4 |
campylobacter |
~15 cases (0.02 per 100,000 inhab.) |
| 5 |
hepatitis A |
~2 cases (0.003 per 100,000 inhab.) |
Source:
- Report of the French
sanitary agencies (http://www.invs.sante.fr/publications/2004/inf_origine_alimentaire/inf_origine_alimentaire.pdf)
INVS/Afssa (PDF file, 192p, 660 KB, in French)
- Sumup of the report (http://www.invs.sante.fr/publications/2004/inf_origine_alimentaire/grilleLecture.pdf)
(PDF file, 5p, 60 KB, in French)
Symptoms typically begin several hours after ingestion and depending on the agent involved, can include one or more of the following: nausea, abdominal pain, vomiting, diarrhea, fever,
headache or tiredness. In most cases the body is able to permanently recover after a short period of acute discomfort and illness. However, foodborne illness can result in permanent health problems
or even death, especially in babies, pregnant
women (and their fetuses), elderly people, sick people and others with weak
immune systems. Similarly, people with liver disease are especially susceptible to infections from Vibrio vulnificus, which can be found in oysters.
Incubation period
The delay between consumption of a contaminated food and appearance of the first symptoms of illness is called the incubation
period. This ranges from hours to days (and rarely years), depending on the agent, and on how much was consumed.
During the incubation period, microbes pass through the stomach into the intestine, attach to the cells lining the intestinal walls, and begin to multiply there. Some types
of microbes stay in the intestine, some produce a toxin that is absorbed into the
bloodstream, and some can directly invade the deeper body tissues. The symptoms produced
depend on the type of microbe. [2] (http://www.cdc.gov/ncidod/dbmd/outbreak/guide_fd.htm)
Infectious dose
The infectious dose is
the amount of agent that must be consumed to give rise to symptoms of foodborne illness. The infective dose varies according to
the agent and consumer's age and health. In the case of Salmonella, as few as
15-20 cells may suffice [3] (http://www-micro.msb.le.ac.uk/video/Salmonella.html).
Pathogenic agents
Bacterial infection is the most common cause of food poisoning. In the United Kingdom during 2000 the individual bacteria involved were as
follows: Campylobacter jejuni 77.3%, Salmonella 20.9%, Escherichia coli O157:H7 1.4%, and all others less than 0.1% [4] (http://www.food.gov.uk/science/sciencetopics/microbiology/58736).
Symptoms for bacterial infections are delayed because the bacteria need time to multiply. They are usually not seen until
12-36 hours after eating contaminated food.
Common bacterial foodborne pathogens are:
In addition to disease caused by direct bacterial infection, some foodborne illnesses are caused by exotoxins which are
excreted by the cell as the bacterium grows. Exotoxins can produce illness even
when the microbes that produced them have been killed. Symptoms typically appear after 1-6 hours depending on the amount of toxin
ingested.
For example Staphylococcus aureus produces a toxin
that causes intense vomiting. The rare but potentially deadly disease botulism occurs when the anaerobic
bacterium Clostridium botulinum grows in improperly
canned low-acid foods and produces a powerful paralytic toxin.
Preventing bacterial food poisoning
The prevention is mainly the role of the state, through the definition of strict rules of hygiene and a public service of veterinary survey of the food chain, from farming to the transformation industry and the delivery (shops and restaurants). This regulation includes:
- traceability: in a final product, it must be possible to know the
origin of the ingredients (originating farm, identification of the harvesting or of the animal) and where and when it was
processed; the origin of the illness can thus be tracked and solved (and possibly penalized), and the final products can be
removed from the sale if a problem is detected;
- respect of hygiene procedures like HACCP and the "cold chain";
- power of control and of law enforcement of the veterinarians.
At home, the prevention mainly consists of:
- the respect of the food storage and food preservation methods (especially refrigeration), and checking the expiration date;
- washing the hands before preparing the meal and before eating;
- washing the fresh vegetables with clear water, especially when not cooked (e.g. fruits, salads);
- washing the dishes after use;
- keeping the kitchen clean.
Bacteria need warmth, moisture, food and
time to grow. The presence, or absence, of oxygen, salt, sugar and acidity are also important factors for growth. In the right
conditions, one bacterium can multiply using binary fission to become
four million in eight hours. Since bacteria can be neither smelled nor seen, the best way to ensure that
food is safe is to follow principles of good food hygiene. This includes not allowing
raw or partially cooked food to touch dishes, utensils, hands or work surfaces previously used to handle even properly cooked or ready to eat food.
High salt, high sugar or high acid levels keep bacteria from growing, which is why salted meats, jam, and pickled vegetables are traditional preserved foods.
The most frequent causes of bacterial foodborne illness are cross-contamination and inadequate temperature control. Therefore control of these two matters is especially important.
Thoroughly cooking food until it is piping hot, i.e. above 70°C (158°F) will
quickly kill virtually all bacteria, parasites or viruses, except for Clostridium botulinum and Clostridium perfringens, which produces a heat-resistant spore that survives temperatures up to 100°C (212°F). Once cooked, hot foods should be kept hot - above 63°C (145°F)
stops microbial growth.
Cold foods should be kept cold, below 5°C (41°F). However, Listeria monocytogenes and Yersinia enterocolitica can both grow at refrigerator temperatures.
Viral infections make up perhaps one third of cases of food poisoning in developed countries. They are usually of
intermediate (1-3 days) incubation period, cause illnesses which
are self-limited in otherwise healthy individuals, and are similar to the bacterial forms described above.
Most foodborne parasites are zoonoses.
See also: Tapeworm
Other
- Anisakis sp.
- Cyclospora
cayetanensis
- Diphyllobothrium
sp.
- Eustrongylides sp.
- Nanophyetus sp.
Natural toxins
In contrast several foods can naturally contain toxins that are not produced by
bacteria and occur naturally in foods, these include:
Other pathogenic agents
Outbreaks
The vast majority of reported cases of foodborne illness occur as individual or sporadic cases. In most cases these
originate, and occur, in the home. An outbreak occurs when two or more people suffer
foodborne illness after consuming food from a contaminated batch.
Often, a combination of events contributes to an outbreak, for example, food might be left at room temperature for many hours,
allowing bacteria to multiply which is compounded by inadequate cooking
which results in a failure to kill the dangerously elevated bacterial levels.
Outbreaks are usually identified when those affected know each other. However, some are identified by public health staff from unexpected increases in laboratory results for certain
strains of bacteria.
Political issues
United Kingdom
Since the 1970s, key changes in UK food safety law have taken place following serious outbreaks of food poisoning. These
included the death of 19 patients in the Stanley Royd Hospital outbreak [5] (http://briandeer.com/social/stanley-royd.htm); and the death of 17 people in the 1996 Wishaw outbreak of E.coli O157 [6] (http://www.scotland.gov.uk/deleted/library/documents-w4/pgr-00.htm), which was a precursor to
the establishment of the independent Food Standards
Agency which is dedicated to the interests of consumers.
United States
In 2001, the Center for Science in the Public Interest (CSPI) petitioned the United States Department of
Agriculture to require meat packers to remove spinal cords before
processing cattle carcasses for human consumption, a measure designed to lessen the risk of infection by variant Creutzfeldt-Jakob disease. The petition was supported by
the American Public Health Association, the Consumer Federation of America, the Government Accountability Project, the National
Consumers League, and Safe Tables Our Priority. This was opposed by the National Cattlemen's Beef Association, the National
Renderers Association, the National Meat Association, the Pork Producers Council, sheep raisers, milk producers, the Turkey
Federation, and eight other organizations from the animal-derived food industry. This was part of a larger controversy regarding
the United States' violation of World Health
Organization proscriptions to lessen the risk of infection by variant Creutzfeldt-Jakob disease [7] (http://www.rense.com/general46/usfup.html).
External links
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