Food poisoning and meat microbiology - Gracey's Meat Hygiene - page 255

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Food poisoning and meat microbiology*

Part 1: Food poisoning
Types of food poisoning
Food poisoning includes bacterial and viral infections;
chemical contamination of food, plant or animal toxins;
and food allergies.
Food allergies , or hypersensitivity to certain foodstuffs,
are not uncommon and together with other allergic dis-
eases may be increasing. The allergens are generally pro-
tein in nature, for example, milk, eggs, cheese, fish,
shellfish and pork, but also mushrooms, tomatoes, etc.
Hypersensitivities to nuts, such as peanuts, are well docu-
mented, and food ingredients are carefully scrutinised by
susceptible individuals. In some cases, the reaction can be
so acute and severe as to require a few individuals to carry
acute medical supplies. Nuts and cereals are also vehicles
for aflatoxin produced during the growth of fungi, either
before or after harvest. The tendency to sensitivity to cer-
tain foodstuffs may be hereditary, and a documented case
in the literature describes an allergy to hens' eggs which
persisted throughout four generations. As many as 30%
of all people may be allergic to one or more foodstuffs.
Chemical contamination is not common and usually
occurs by accidental contamination, through fraud or per-
haps some unintentional chemical reaction between a
foodstuff and its container. The metals encountered include
copper, lead, arsenic and antimony. In England and Wales,
outbreaks caused by chemical contamination have been
due to the presence of zinc in acid fruits which have been
stored or cooked in galvanised containers. In Germany,
the storage of prepared foodstuffs in zinc containers is
prohibited by law. Water is at particular risk from chemical

contamination (usually accidental) such as by aluminium
or phenols. Lead may, of course, be leached from lead pipes
or even from soldered lead capillary joints. Not only metals
are involved; a large outbreak of illness occurred in Spain
following chemical adulteration of cooking oil.
Inherently poisonous substances can occur in nor-
mally edible plants and animals including certain fungi,
berries, fish and shellfish. This is well recognised in the
case of mushrooms, where some types are toxic. Less
well known are foods that are poisonous unless properly
prepared, for example, red kidney beans. Other foods in
the right circumstances can acquire toxins from the
environment. This is a particular problem with shellfish,
which can filter out the algal toxins that cause paralytic
and diarrhoetic shellfish poisoning in consumers. In
some instances, breakdown products can produce ill-
ness, as in the case of scombrotoxin poisoning when
bacterial action in scromboid fish, such as mackerel
and tuna, converts histidine to histamine. A similar type
of illness has been associated with cheese.

Surveillance of food poisoning
There are several different methods of gathering statis-
tics on food-borne disease, and it is important to recog-
nise the limitations posed by each of these. The three
most important sources of data are:

1 Notifications of food poisoning
2 Surveillance of laboratory-confirmed infections
3 Investigation of outbreaks of food poisoning

Each of these surveillance methods provides valuable,
but incomplete, information, and none on its own will
measure the true extent of all food-borne disease.
Specifically, most of the information gathered relates to

*Additional editing by Malcolm J Taylor, Senior Scientific Officer, Food
Science Branch, Agri-Food-Biosciences Institute, Belfast BT9 5PX, UK.