I
FOOT
astrovirus,
rotavirus,
and
a
small
round-structured virus (SRSV), w hich
affects shellfish. This form of poison-
ing can occur when raw or partly
cooked foods have been in contact
with water that has been contaminated
by human excrement.
OTHER INFECTIVE CAUSES
The protozoan parasite C
r y p t o s p o r i d i u m
(see
cryptosporidiosis
) ,
w hich p rinci-
pally
affects
farm
animals,
can
be
passed on to humans through drinking
water supplies, swim m ing pools, or by
direct contact w ith infected animals.
People w ith
HIV
infection or
AIDS
are
particularly susceptible to contracting
this type of food poisoning.
NONINFECTIVE CAUSES
There are a number of noninfective
causes
of food poisoning including
poisonous mushrooms and toadstools
(see
mushroom poisoning
) ,
fresh fruit
and vegetables contaminated w ith high
doses of insecticide, and chemical poi-
soning from some foods, such as fruit
juice,
that
are
stored in
containers
made partly from zinc.
Certain foods, such as puffer fish,
considered a delicacy in Japan, or cas-
sava, a staple food in many tropical
countries, can also cause moderate to
lethal poisoning if im properly cooked
or prepared.
SYMPTOMS
The onset of symptoms depends on the
cause of poisoning. Symptoms usually
develop w ithin 30 minutes in cases of
chemical poisoning, between one and
1 2
hours in cases of bacterial toxins,
and between
12 and 48 hours with
most bacterial and viral infections.
Symptoms of food poisoning usually
include diarrhoea, nausea and vom it-
ing, stomach pain, and, in severe cases,
shock
and collapse. Botulism affects the
nervous system, causing visual distur-
bances, difficulty with speech, para-
lysis, and vomiting.
DIAGNOSIS
The diagnosis of bacterial food poison-
ing
can usually be
confirmed from
examination
of a sample
of faeces.
Chemical poisoning can often be diag-
nosed from a description of what the
person has eaten, and from analysis of a
sample of the suspect food.
TREATMENT
M ild cases can be treated at home by
replacement of lost fluids (see
rehydra-
tion therapy
) .
In severe cases, or when
the very young or elderly are affected,
hospital treatment may be necessary. If
poisoning by a chemical or bacterial
toxin is suspected, the stomach may be
washed out (see
lavage, gastric).
Except for botulism and some cases
of mushroom poisoning, most food
poisoning is not serious; recovery usu-
ally occurs w ithin about three days.
Some strains of E.
c o i i
can seriously
damage red blood cells, causing
kidney
failure
(see
haemolytic-uraemic syndrome).
(See also
cholera; dysentery; seafood poi-
soning; typhoid fever.)
PREVENTION
Some
simple
measures
can virtually
eliminate the risk of food poisoning.
Hands should always be washed before
food is handled, and fresh fruit and
vegetables should be rinsed in clean
water. Cutting boards and implements
that
have
been
used for
raw
meat
should be washed w ith hot water be-
fore being used for other foods. Meat,
poultry, and eggs must be cooked thor-
oughly. Raw and cooked foods should
be stored well apart in the refrigerator,
and raw meat should be kept in the
coldest part. Advice should be sought
when preparing unfamiliar foods.
foot
The foot has two vital functions. The
first of these functions is to support
the weight of the body in standing or
ANATOMY OF THE FOOT
An adult has
2 6
bones (about one
eighth of the total number in the
entire skeleton) in each foot. The
calcaneus is attached to the talus
above. In front are the navicular,
cuboid, and cuneiform bones, which
are attached to the metatarsals. The
phalanges form the toes.
walking; the second function of the
foot is to act as a lever that propels the
body forwards.
STRUCTURE
The largest bone of the foot, the heel-
bone (see
calcaneus),
is jointed with
the ankle bone (the talus). The tarsal
bones are located in front of the talus
and calcaneus and they are jointed to
the five
metatarsal bones.
The bones of
the toes are called the
phalanges;
the
big toe has two phalanges and all the
remaining toes have three.
Tendons passing around the ankle
connect the muscles that act on the
various bones of the foot and toe. The
main blood vessels and nerves pass in
front of and behind the inside of the
ankle to supply the foot. The under-
surface
of a
norm al
foot forms
a
natural arch that is supported by liga-
ments
and muscles.
Fascia
(fibrous
tissue) and fat form the sole of the
foot, w hich is covered by a layer of
tough skin.
DISORDERS
Injuries to the foot often result in
frac-
ture
of the foot bones (the metatarsals
and
phalanges). The
calcaneus
may
fracture following a fall from a height
on to a hard surface.
Congenital
foot
abnormalities
are
fairly common and include club-foot
(see
talipes), flat-feet,
and
claw-foot.
A
bunion
is a common deformity of the
foot in w hich a thickened
bursa
(fluid-
filled pad) lies over the joint at the base
of the big toe.
Corns
are small areas of thickened
skin that are usually caused by tightly
fitting
shoes.
Verrucas
(see
plantar
warts
) develop on the soles of the feet.
Athlete’s foot
is a fungal infection that
affects
the
skin
between
the
toes,
causing it to become very itchy, sore,
and cracked.
Gout
is a relatively common type of
arthritis that often affects the joint at
the base of the big toe or one of the
joints in the foot. An ingrowing toenail
(see
toenail, ingrowing
) commonly oc-
curs on the big toe and may lead to
inflammation
and
infection
of the
surrounding tissues (see
paronychia).
Foot-drop
is the inability to raise the
foot properly causing it to drag along
the ground when the person is walk-
ing. The
condition may occur as a
result of damage to the muscles in the
leg that are responsible for performing
this movement or, alternatively, to the
nerves that supply these muscles.
F
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