Protist diseases: The pathogens that cause malaria are protists.

The idea

This statement identifies the type of pathogen responsible for malaria. Malaria is caused by single-celled eukaryotic organisms called protists, specifically species of Plasmodium. A protist is not a bacterium, virus or fungus; it is a eukaryotic microorganism, so it has a nucleus and other membrane-bound organelles. The malarial protist enters the human blood when an infected mosquito bites and feeds. Inside the human body it invades red blood cells, multiplies and causes the recurring fever and other symptoms of malaria. Because the pathogen is a protist, antibiotics that target bacteria are not effective against it. Recognising the pathogen type helps explain transmission, symptoms and why control focuses on mosquitoes and protective drugs.

What earns the marks

• Malaria is caused by a protist pathogen, for example Plasmodium.
• Protists are eukaryotic, single-celled organisms with a nucleus.
• The malarial protist is transmitted to humans by mosquitoes and infects red blood cells.
• Because the pathogen is a protist, antibacterial antibiotics are not an effective treatment.
• Identifying the pathogen type helps explain the disease symptoms and the methods used to control it.

Common mistakes and how to put them right

• Naming a virus or bacterium as the cause of malaria.

  Put it right: The pathogen is a protist.

• Thinking that the mosquito is the pathogen.

  Put it right: The mosquito is the vector that transmits the protist.

• Assuming antibiotics cure malaria.

  Put it right: Antibiotics act on bacteria, so they do not kill the malarial protist.

Exam tips

• Write 'protist' clearly and, if asked for an example, name Plasmodium.
• Distinguish the pathogen from the vector by using the terms correctly in the same answer.
• Link the pathogen type to treatment, noting that antibiotics are ineffective against protists.