Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.

Briefly describe the important roles that water plays in the human body

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    Water plays the following roles in the human body

For which of the following diseases will the construction and appropriate utilisation of latrines (instead of open defecation) reduce transmission? Give reasons for your choice.

  1. amoebiasis
  2. dracunculiasis
  3. schistosomiasis
  4. malaria
  5. giardiasis.

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1. amoebiasis, 3. schistosomiasis and 5. giardiasis can be transmitted through faecal matter from infected persons entering water sources, hence the construction and use of latrines would help to reduce their transmission.

2. dracunculiasis is caused by consuming water that contains copepods and is not related to human faecal contamination; d. malaria is transmitted by the Anopheles mosquito, which breeds in stagnant water. Latrines would not have any impact on these two diseases.

Read Case Study 2.1 and answer the questions that follow.

Case Study 2.1

Abebe is a 25-year-old man originally from Zegie, Lake Tana. He lives on the outskirts of the city of Bahir Dar in a single room together with his two friends. He is a daily labourer. In the compound of the house where they live, there is no space to construct a latrine. Thus, all the people in the compound defecate in the open area nearby.

Because of the long journey home from Bahir Dar to Zegie, he seldom visits his family. The family grows and sells coffee and khat for their living. Abebe’s family does not have a latrine either and uses an open field. During a recent visit to his family, he swam in Lake Tana and washed his clothes there. Upon returning to Bahir Dar, Abebe became sick, having severe abdominal pain, diarrhoea, joint pain, headache, and fever. The next morning, his friends took him to the nearest health centre and he got some medication.

  1. What is the most important public health issue you see in this case study?
  2. What specific water-associated diseases do you expect Abebe might have?
  3. What do you think are the causes of these problems?

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  1. The issue of open defecation is the most important public health issue as this leads to disease.
  2. Abebe may have caught a waterborne disease (e.g. diarrhoeal disease such as cholera or typhoid), a water-based disease (e.g. bilharzia), or a water-related disease (e.g. malaria).
  3. Open defecation may have contaminated the water in Lake Tana, making anyone using the water vulnerable to disease. The lake could also be a breeding ground for mosquitoes that cause malaria, or snails that carry bilharzia.

Which of the following statements is false? In each case explain why it is incorrect.

  1. E. coli is a type of virus found in faeces.
  2. Faecal coliforms are typically found in human and animal faeces.
  3. The presence of E. coli in a water sample means the water is safe to drink.
  4. The absence of E. coli in a water sample means the water is safe to drink.

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1 is false. E. coli is a type of bacterium, not a type of virus.

3 is false. If a water sample is positive for E. coli this indicates faecal contamination, which means it is likely that pathogens are present in the water.

4 is also false. The absence of E. coli indicates the water is not contaminated with bacteria of faecal origin but it does not mean the water is necessarily safe to drink because it may still contain pathogens.