Malaria is a communicable disease caused by the protist Plasmodium, which is spread to humans through the bite of infected female Anopheles mosquitoes. Explain how the spread of malaria can be reduced, and describe the non-specific defences the human body uses if Plasmodium enters the bloodstream.

Pearson Edexcel A-Level Biology A (9BI0) — 5.2 Pathogens and infection · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Malaria kills over 600,000 people worldwide each year, predominantly in tropical regions where the Anopheles mosquito is found. Unlike bacterial or viral diseases, malaria is caused by a protist pathogen transmitted by an animal vector.

Model answer (5 marks)

1. Reduce the mosquito vector – drain standing water, use insecticides and insecticide‑treated nets to stop bites.
2. The skin is a physical barrier that prevents Plasmodium from entering the body.
3. If Plasmodium enters the blood, phagocytic white blood cells engulf and destroy it by phagocytosis.
4. B‑lymphocytes recognise Plasmodium antigens and produce specific antibodies.
5. Antibodies bind to the antigens on Plasmodium, neutralising it or marking it for destruction and triggering further immune responses.

Examiner tips

  • Use the exact terminology (phagocytosis, B‑lymphocytes, antibodies).
  • Show the causal link between vector control and reduced transmission.
  • Include both physical and cellular immune defences.
  • Keep each point brief and separate with numbers.

Mark scheme (5 marks)

  1. Controlling the mosquito vector reduces spread — e.g. draining standing water / using insecticides / mosquito nets to prevent bites
  2. The skin acts as a physical barrier preventing Plasmodium from entering the body
  3. If Plasmodium enters the blood, white blood cells (phagocytes) engulf and destroy the pathogen by phagocytosis
  4. B-lymphocytes detect the antigens on the surface of Plasmodium and produce specific antibodies
  5. Antibodies bind to the antigens on Plasmodium, neutralising or marking it for destruction / triggering an immune response

Key terms in this question

communicable disease · protist · non-specific defence

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