Food poisoning
Practical Action
equipment, and to stop anyone with a stomach complaint from handling processed food.
Personal hygiene of the food handlers must be very high.
The symptoms of Salmonella poisoning are diarrhoea, vomiting and fever and occur 10-24 hours
after eating the poisoned food and last for 48-96 hours. Salmonella poisoning may be fatal to the
very old, very young or the infirm so particular care is needed when making infant foods or
weaning foods.
Shigella
This is a bacterium associated with sewage. Poisoning is caused by direct contact of food with
sewage or by indirect contact (for example by operators' hands, equipment or by contaminated
water). Personal hygiene and correct water treatment are therefore essential to prevent poisoning.
Shigella is found where poor hygiene exists.
The symptoms are diarrhoea, fever and nausea which appear from 7 hours to 7 days after eating
contaminated food. They may last for a week but are rarely fatal. Any food that requires manual
preparation is a potential source.
Escherichia coli
This bacterium is also associated with sewage contamination of foods, water or poor personal
hygiene. The bacteria themselves can cause food poisoning or they can produce a poison in the
gut. The most common food source is red meat which is contaminated at slaughter. Meat
products (for example sausages) as well as dairy products (especially cheese) are also potential
sources of food poisoning. Other sources (for example pasteurised milk, ice cream, cooked
meats) indicate contamination after processing and hence poor hygiene by the food handlers.
Campylobacter fetus
The most common sources of this bacterium are contaminated water and unpasteurised milk,
although poultry and other meats are also important sources. Proper chlorination of water and
heating of foods will destroy these bacteria. Illness occurs 2-5 days after eating contaminated
food and symptoms are diarrhoea, muscle pain and headaches with vomiting. It is usually brief
and not fatal.
Clostridium perfringens
The most frequent cause of this type of poisoning is slow and inadequate cooking of meats. The
bacteria produce spores which rapidly germinate after eating and produce a poison in the gut. It
can be prevented by good sanitation, by heating food adequately and keeping cooked food cool
(below 10°C) or hot (above 60°C).
The symptoms are stomach cramps without vomiting and diarrhoea. They appear within 8-24
hours of eating contaminated food and last for 24 hours. The illness is not fatal.
Clostridium botulinum
Botulism is a rare but serious paralytic illness caused by a nerve toxin that is produced by the bacterium
Clostridium botulinum. There are three main kinds of botulism:
• Food-borne botulism is caused by eating foods that contain the botulism toxin.
• Wound botulism is caused by toxin produced from a Clostridium botulinum -infected wound.
• Infant botulism is caused by consuming the spores of the botulinum bacteria which then grow
in the intestines and release the toxin.
All forms of botulism can be fatal and are considered medical emergencies. This is a serious type of food
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