foodborne illness

Transmission

Ill food handlers are one of the most common sources of foodborne illnesses. Some common diseases are occasionally transmitted to food through the water vector. These include infections caused by Shigella, Hepatitis A and the parasites Giardia lamblia and Cryptosporidium parvum. Contact between food and pests, especially flies, rodents and cockroaches, are other food contamination vectors.

Foodborne illness can also be caused by the presence of pesticides or medicines in food, or by unintentionally consuming naturally toxic substances like poisonous mushrooms or reef fish.

Symptoms and mortality

Symptoms typically begin several hours to several days after ingestion and depending on the agent involved, can include one or more of the following: nausea, abdominal pain, vomiting, diarrhoea, gastroenteritis, fever, headache or fatigue. 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. Foodborne illness is a major cause of reactive arthritis, which typically occurs 1–3 weeks afterward. Similarly, people with liver disease are especially susceptible to infections from Vibrio vulnificus, which can be found in oysters or crabs.

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 months or even years, such as in the case of Listeriosis or Creutzfeldt-Jacob disease), depending on the agent, and on how much was consumed. If symptoms occur within 1–6 hours after eating the food, it suggests that it is caused by a bacterial toxin or a chemical rather than live bacteria.

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. [1]

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 overall health. In the case of Salmonella, in healthy human volunteers, a relatively large inoculum of 10 million to 100 million organisms is necessary to produce symptoms[2], as Salmonellae are very acid sensitive. So, an artificially higher stomach pH level greatly reduces the number of bacteria required to cause symptoms (by 10- to a 100-fold).

Pathogenic agents

See also: Pathogen

An early theory on the causes of food poisoning involved ptomaines, alkaloids found in decaying animal and vegetable matter. While some poisonous alkaloids are the cause of poisoning, the discovery of bacteria left the ptomaine theory obsolete.

Bacteria

Bacteria are a common cause of foodborne illness. 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% [3]. In the United States, noroviruses are the most common cause of foodborne illness, causing 57% of outbreaks in 2004. In the past, bacterial infections were thought to be more prevalent because few places had the capability to test for norovirus and no active surveillance was being done for this particular organism. Symptoms for bacterial infections are delayed because the bacteria need time to multiply. They are usually not seen until 12–72 hours or more after eating contaminated food.

Common bacterial foodborne pathogens are:

• Bacillus cereus
• Campylobacter jejuni which can lead to secondary Guillain-Barré syndrome

• Escherichia coli O157:H7 enterohemorrhagic (EHEC) which causes hemolytic-uremic syndrome
• Escherichia coli - enteroinvasive (EIEC)
• Escherichia coli - enteropathogenic (EPEC)
• Escherichia coli - enterotoxigenic (ETEC)
• Escherichia coli - enteroaggregative (EAEC or EAgEC)

• Listeria monocytogenes
• Salmonella spp.
• Shigella spp.
• Streptococcus
• Vibrio cholerae, including O1 and non-O1
• Vibrio parahaemolyticus
• Vibrio vulnificus
• Yersinia enterocolitica and Yersinia pseudotuberculosis

Less common bacterial agents:

• Brucella spp.
• Corynebacterium ulcerans
• Coxiella burnetii or Q fever
• Plesiomonas shigelloides

Exotoxins

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.

• Clostridium botulinum
• Clostridium perfringens
• Staphylococcus aureus
• Bacillus cereus

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 botulin, a powerful paralytic toxin.

Emerging foodborne pathogens

Much is still not known about foodborne illness. Approximately sixty percent of outbreaks are still caused by unknown sources.

• Aeromonas hydrophila, Aeromonas caviae, Aeromonas sobria

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 good food safety practices.

In August 2006, the United States Food and Drug Administration approved Phage therapy which involves spraying meat with viruses that infect bacteria, and thus prevents infection with bacteria. This has raised concerns since without mandatory labelling consumers won't be aware that meat and poultry products have been treated with the spray. [4]

Viruses

Viral infections make up perhaps one third of cases of food poisoning in developed countries (In the US more than 50% of cases are viral). 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.

• Rotavirus
• Hepatitis A is distinguished from other viral causes by its prolonged (2–6 week) incubation period and its ability to spread beyond the stomach and intestines, into the liver. It often induces jaundice, or yellowing of the skin, and rarely leads to chronic liver dysfunction.
• Hepatitis E

Parasites

Most foodborne parasites are zoonoses.

Platyhelminthes:

• Diphyllobothrium sp.

• Nanophyetus sp.
• Taenia saginata
• Taenia solium
• Fasciola hepatica

See also: Tapeworm and Flatworm

Nematode:

• Anisakis sp.
• Ascaris lumbricoides
• Eustrongylides sp.
• Trichinella spiralis
• Trichuris trichiura

Protozoa:

• Acanthamoeba and other free-living amoebae
• Cryptosporidium parvum
• Cyclospora cayetanensis
• Entamoeba histolytica
• Giardia lamblia
• Sarcocystis hominis
• Sarcocystis suihominis
• Toxoplasma gondii

Natural toxins

In contrast several foods can naturally contain toxins that are not produced by bacteria and occur naturally in foods, these include:

• Aflatoxins
• Alkaloids
• Ciguatera poisoning
• Grayanotoxin (honey intoxication)
• Mushroom toxins
• Phytohaemagglutinin (Red kidney bean poisoning)
• Pyrrolizidine alkaloid
• Shellfish toxin, including Paralytic shellfish poisoning, Diarrhetic shellfish poisoning, Neurotoxic shellfish poisoning, Amnesic shellfish poisoning and Ciguatera fish poisoning
• Scombrotoxin
• Tetrodotoxin (Fugu fish poisoning)

Other pathogenic agents

• Prions, resulting in Creutzfeldt-Jakob disease

Global Impact

Nowadays, rapid globalization of food production and trade has increased the potential likelihood of food contamination. Many outbreaks of foodborne diseases that were once contained within a small community may now take place on global dimensions. Food safety authorities all over the world have acknowledged that ensuring food safety must not only be tackled at the national level but also through closer linkages among food safety authorities at the international level. This is important for exchanging routine information on food safety issues and to have rapid access to information in case of food safety emergencies."

It is difficult to estimate the global incidence of foodbourne disease, but it has been reported that in the year 2000 about 2.1 million people died from diarrhoeal diseases. Many of these cases have been attributed to contamination of food and drinking water. Additionally, diarrhoea is a major cause of malnutrition in infants and young children.

Even in industrialized countries, up to 30% of the population of people have been reported to suffer from foodborne diseases every year. In the U.S, around 76 million cases of foodborne diseases, which resulted in 325,000 hospitalizations and 5,000 deaths, are estimated to occur each year. Developing countries in particular,are worst affected by Foodborne illnesses due to the presence of a wide range of dieases, including those caused by parasites. Foodborne illnesses can and did inflict serious and extensive harm on society. In 1994, an outbreak of salmonellosis due to contaminated ice cream occurred in the USA, affecting an estimated 224,000 persons. In 1988, an outbreak of hepatitis A, resulting from the consumption of contaminated clams, affected some 300,000 individuals in China.

Food contamination creates an enormous social and economic strain on societies. In the U.S., diseases caused by the major pathogens alone are estimated to cost up to US $35 billion annually (1997) in medical costs and lost productivity. The re-emergence of cholera in Peru in 1991 resulted in the loss of US $500 million in fish and fishery product exports that year.

Statistics

Every year there are about 76 million foodborne illnesses in the United States (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, there are approximately 76 million foodborne illnesses (26,000 cases for 100,000 inhab.):

• 325,000 were hospitalized (111 per 100,000 inhab.);
• 5,000 people died (1.7 per 100,000 inhab.).
• Major pathogens from food borne illness in the United States cost upwards of US $35 billion dollars in medical costs and lost productivity (1997)

Source:

• Food safety and foodborne illness, WHO

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 hospitalized (24 per 100,000 inhab.);
• 400 people died (0.9 per 100,000 inhab.).

The causes of the illness (toxic factor) are:

The causes of death by foodborne illness are:

Source:

• Report of the French sanitary agencies INVS/Afssa (PDF file, 192p, 660 KB, in French)
• Sumup of the report (PDF file, 5p, 60 KB, in French)

Outbreaks

The vast majority of reported cases of foodborne illness occur as individual or sporadic cases. The origin of most sporadic cases is undetermined. In the United States, where people eat outside the home frequently, most outbreaks (58%) originate from commercial food facilities (2004 FoodNet data). An outbreak is defined as occurring when two or more people experience similar illness after consuming food from a common source.

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, more and more, outbreaks are identified by public health staff from unexpected increases in laboratory results for certain strains of bacteria. Outbreak detection and investigation in the United States is primarily handled by local health jurisdictions and is inconsistent from district to district. It is estimated that 1–2 % of outbreaks are detected.

Ptomaine

"Ptomaine" is a former name for a supposed group of chemical substances that were theorized to cause food poisoning. The word "ptomaine" is no longer used scientifically.

Political issues

United Kingdom

Since the 1970's, key changes in UK food safety law have taken place following serious outbreaks of foodborne illness. These included the death of 19 patients in the Stanley Royd Hospital outbreak [5]; and the death of 17 people in the 1996 Wishaw outbreak of E.coli O157 [6], which was a precursor to the establishment of the Food Standards Agency which, according to Tony Blair in the 1998 white paper A Force for Change Cm 3830 "would be powerful, open and 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].

Organizations

World Health Organization Food Safety Department The WHO provides scientific advice for organizations and the public on issues concerning the safety of food. It serves as a medium linking the food safety systems in countries around the world. Food safety is currently one of WHO's top ten priorities.Food Safety is one of the major issues in our world today, and the Organization calls for more systematic and aggressive steps to be taken to significantly reduce the risk of foodborne diseases.

The Department of Food Safety, Zoonoses and Foodborne Diseases The Department of Food Safety, Zoonoses and Foodborne Diseases is a department under the WHO. Its mission is to: to reduce the serious negative impact of foodborne diseases worldwide. According to the WHO website, Food and waterborne diarrhoeal diseases are leading causes of illness and death in less developed countries, killing approximately 1.8 million people annually, most of whom are children "WHO works closely with the Food and Agriculture Organization of the United Nations (FAO) to address food safety issues along the entire food production chain--from production to consumption--using new methods of risk analysis. These methods provide efficient, science-based tools to improve food safety, thereby benefiting both public health and economic development."

The International Food Safety Authorities Network (INFOSAN) This Network is is intended to complement and support the existing WHO Global Outbreak Alert and Response Network (GOARN) which includes a Chemical Alert and Response component.