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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