Foodborne illnesses
Foodborne illness (also
foodborne disease and colloquially referred to as food poisoning) is any
illness resulting from the consumption of food that is contaminated by
pathogenic bacteria, viruses, or parasites.
Causes
Foodborne illness
usually arises from improper handling, preparation, or food storage.
Good hygiene practices before, during, and after food preparation can
reduce the chances of contracting an illness. There is a consensus in
the public health community that regular hand-washing is one of the most
effective defenses against the spread of foodborne illness. The action
of monitoring food to ensure that it will not cause foodborne illness is
known as food safety. Foodborne disease can also be caused by a large
variety of toxins that affect the environment. For foodborne illness
caused by chemicals, see Food contaminants. Foodborne illness can also
be caused by pesticides or medicines in food and naturally toxic
substances like poisonous mushrooms or reef fish.
Common Foodborne Illness
Bacteria
- Campylobacter jejuni
- Clostridium perfringens
- Salmonella spp. – its S. typhimurium infection is caused by consumption of eggs or poultry that are not adequately cooked
- Salmonella Escherichia coli O157:H7 enterohemorrhagic (EHEC) which causes hemolytic-uremic syndrome
- Bacillus cereus
- Listeria monocytogenes
- Shigella spp.
- Staphylococcus aureus
- Streptococcus
- Vibrio cholerae, including O1 and non-O1
- Vibrio parahaemolyticus
- Vibrio vulnificus
- Yersinia enterocolitica
- Yersinia pseudotuberculosis
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 24 hours
depending on the amount of toxin ingested.
- Clostridium botulinum
- Clostridium perfringens
- Staphylococcus aureus
- Bacillus cereus
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 and noroviruses are the most
common foodborne illness, causing 57% of outbreaks in 2004. Foodborne
viral infection are usually of intermediate (1–3 days) incubation
period, causing illnesses which are self-limited in otherwise healthy
individuals, and are similar to the bacterial forms described above.
- Enterovirus
- 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.
The virus has been found to cause the infection due to the consumption
of fresh-cut produce which has fecal contamination.
- Norovirus
- Rotavirus
Parasites
Most foodborne parasites are zoonoses.
- Platyhelminthes:
- Diphyllobothrium sp.
- Nanophyetussp.
- Taenia saginata
- Taenia solium
- 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
Natural toxins
Several foods can
naturally contain toxins, many of which are not produced by bacteria.
Plants in particular may be toxic; animals which are naturally poisonous
to eat are rare. In evolutionary terms, animals can escape being eaten
by fleeing; plants can use only passive defenses such as poisons and
distasteful substances, for example capsaicin in chili peppers and
pungent sulfur compounds in garlic and onions. Most animal poisons are
not synthesised by the animal, but acquired by eating poisonous plants
to which the animal is immune, or by bacterial action.
- Alkaloids
- Ciguatera poisoning
- Grayanotoxin (honey intoxication)
- Mushroom toxins
- Phytohaemagglutinin (red kidney bean poisoning; destroyed by boiling)
- Pyrrolizidine alkaloids
- Shellfish toxin, including paralytic shellfish poisoning,
diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, amnesic
shellfish poisoning and ciguatera fish poisoning
- Scombrotoxin
- Tetrodotoxin (fugu fish poisoning)
- Some plants contain substances which are toxic in large doses, but have therapeutic properties in appropriate dosages.
- Foxglove contains cardiac glycosides
- Poisonous hemlock (conium) has medicinal uses.
Mechanism
The delay between
consumption of a contaminated food and the 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.
The long incubation period of many foodborne illnesses tends to cause sufferers to attribute their symptoms to "stomach flu".
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.
Infectious dose
The infectious dose is
the amount of agent that must be consumed to give rise to symptoms of
foodborne illness, and varies according to the agent and the consumer's
age and overall health. In the case of Salmonella a relatively large
inoculum of 1 million to 1 billion organisms is necessary to produce
symptoms in healthy human volunteers, as Salmonellae are very sensitive
to acid. An unusually high stomach pH level (low acidity) greatly
reduces the number of bacteria required to cause symptoms by a factor of
between 10 and 100.
Epidemiology team or EPI Team
Rockingham County has a
Multi-disciplinary team always ready to investigate any communicable
disease outbreaks within the county. This team consists of nurses,
public information officer, environmental health specialists, lab
technicians and administrative staff.