Controlling endemic diseaseEdexcel A-Level Biology B: Subtopic test

1. 1
   In a trial in a malaria-endemic region, researchers gave insecticide-treated bed nets to the families in 20 villages. Another 20 similar villages received no nets during the trial and were given nets afterwards. Before the trial, the average number of malaria cases per 1000 children per year was 310 in the villages that were given nets and 300 in the other villages. One year later it was 140 in the villages with nets and 290 in the other villages.

   (a)

   Which organism must the bed nets protect people against to reduce the transmission of malaria?

   [1 mark]

   • ATsetse fly
   • BHousefly
   • CAphid
   • DFemale Anopheles mosquito

   (b)

   Why did the researchers include 20 villages that were not given nets during the trial?

   [1 mark]

   • ATo provide a supply of mosquitoes
   • BTo make sure all villagers received treatment equally
   • CTo act as a control so that any change can be linked to the nets
   • DTo measure the cost of the nets

   (c)

   Calculate the percentage reduction in malaria cases per 1000 children in the villages that were given nets.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A government decides to spray the inside walls of homes with the insecticide DDT to kill Anopheles mosquitoes. DDT is cheap and very effective at first, but it persists in the environment and accumulates in food chains. In some districts the mosquitoes are no longer killed by it.

   (a)

   Which of these is an environmental implication of using DDT to control malaria?

   [1 mark]

   • AIt persists and accumulates in food chains
   • BIt makes the mosquitoes more resistant to every insecticide in the area
   • CIt raises the cost of treating malaria cases
   • DIt increases the number of people who need antimalarial drugs

   (b)

   Which of these is an economic benefit of reducing the number of malaria cases in a region?

   [1 mark]

   • AChildren miss more days at school
   • BFewer working days are lost, so productivity increases
   • CHealth services have to treat more patients
   • DFewer tourists are willing to visit

   (c)

   Suggest why the spraying programme may become less effective over time.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A pharmaceutical company announces that its new malaria vaccine prevents most cases in children. At the same time, a separate research group proposes releasing genetically modified male mosquitoes whose offspring do not survive, in order to reduce the number of Anopheles mosquitoes in one region.

   (a)

   Describe how the scientific community would validate the claim that the new vaccine is effective.

   [3 marks]

   (b)

   Evaluate the social and ethical issues of releasing the genetically modified mosquitoes.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A national malaria control programme has a limited budget. It is choosing between three methods: giving insecticide-treated bed nets to every household, draining the marshes and pools where mosquitoes breed, and giving antimalarial drugs to the whole population.

   (a)

   Explain the social, economic and ethical implications of the three control methods.

   [6 marks]

   (b)

   Evaluate the role of the scientific community in validating these control methods.

   [6 marks]

   Total for question 4: 12 marks

End of questions