Water
& Disease 3:
Parasitic diseases
Parasitic
diseases
Parasitic worms (helminths)
cause many diseases in developing countries. These include ascaris,
whipworm and thread worm, but it is bilharzia, hookworm and guinea worm
that are the most dangerous. As with diarrhoeal diseases these can also
be ____1____ through safe water, effective sanitation and good
____2____.
Bilharzia is a disease
caused by a small flat worm which lives in the veins of pelvic organs.
Over 200 million people are ____3____ across 74 countries and the
disease causes 20,000 deaths a year.
The worm lives in blood
vessels where they excrete between 300 and 3000 ____4____ into the
bloodstream. Some of these eggs then bore into the intestine and are
passed out when people go to the ____5____. If the eggs reach a lake or
stream they hatch into larvea, which are then eaten by snails living in
the water. After developing inside the snails the larvea are eventually
passed back in to the stream or lake where they can ____6____ the skin
of a new person and enter their bloodstream.
Effect on health: Once in the
bloodstream the eggs form clusters on blood vessels damaging the blood
vessel walls. They can also damage the bladder, large intestine, liver
and kidneys. Some eggs can be carried to other parts of the body,
especially the lungs and nervous system, ____7____ these too. They can
also cause chronic diarrhoea.
Prevention: Bilharzia can be
prevented through the use of latrines which stop the eggs getting into
water sources, discouraging people from bathing in infected lakes or
streams, using a safe drinking water supply and snail eradication
programmes.
Guinea worm is a ____8____
disease that enters the human body through ____9____ water. The guinea
worm is a long worm (up to one metre) that lives under the skin. It can
be spread when the sufferer puts the infected area of skin in water,
allowing larvae back in to the drinking water cycle.
The disease has been conquered
in a number of countries and ____10____ the number of cases has fallen
by 97% from 3.5 million to 150,000 during the past ten years. The
United Nations has set a goal for its final eradication. However, the
disease persists in many areas that lack access to adequate water and
____11____.
Effect on health: The worm
causes severe ____12____ and eventually emerges through the skin
leading to ulcers, fevers and other ailments. Guinea worm often
afflicts the most productive family members, especially women, which in
turn leads to childcare and nutritional problems.
Prevention: Guinea worm can be
prevented through safe drinking water and hygiene education.
Hookworms are a very common
example of intestinal parasites which can grow up to 1cm long and 4mm
wide. They are spread when larvea enter the skin, typically through the
soles of feet when people walk ____13___. 900 million people are
affected worldwide. The eggs, which are passed out in human faeces, can
survive for up to three months in the soil.
Effect on health: The worm
lives in the small intestine and attaches itself to the intestine walls
using hooks on its head. One sufferer can carry up to 100 worms at any
time. The hooks pierce the intestine walls allowing the worms to suck
nutrient-rich blood. Each worm can take up to 0.1ml of blood a day,
damaging the intestine wall and reducing the body's ability to absorb
food. Hookworms result in stunted growth in children, loss of blood and
anaemia. In severe cases ____14 ___ can cause heart failure.
Prevention: Hookworms can be
prevented by the use of sanitary latrines. Wearing shoes or sandals to
prevent the worms from penetrating the skin is also very important.
Task
1, Vocabulary: Read the passage and put the words in the box below in
the correct space.
Word
|
Space
in text
|
Word |
Space
in text |
globally
|
|
barefoot |
|
toilet
|
|
hygiene |
|
prevented |
|
damaging |
|
anaemia |
|
infected |
|
pain |
|
eggs |
|
contaminated |
|
parasitic |
|
sanitation |
|
penetrate |
|
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