Protist Diseases (AQA GCSE Biology): Revision Note

Protists: Basics

• Protists are a diverse group of eukaryotic and usually unicellular organisms

• Only a small number of protists are pathogenic, but the diseases they cause are often serious

• Pathogenic protists often need a vector to transfer from one host to the next

Malaria

• The pathogens that cause malaria are protists from the Plasmodium genus (four species); they have a complex life cycle but can infect red blood cells in humans

• The malarial protist has a life cycle that includes the mosquito as a vector

• Malaria causes recurrent episodes of fever and can be fatal in certain instances

• The spread of malaria is controlled by preventing the vectors, mosquitoes, from breeding and by using mosquito nets to avoid being bitten

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Symptoms

• Recurrent fever and shaking when the protists are bursting out of the red blood cells.

• These episodes can weaken the host so much it can be fatal.

How is it spread?

• By the mosquito vector – see the lifecycle diagram.

Treatment & prevention

• If diagnosed early, malaria can be treated with a combination of drugs.

• However, the protists that cause malaria have become resistant to most of the drugs that are available to treat it.

• The spread of malaria can be reduced by controlling mosquito populations:

  • Using insecticides (-cide meaning to kill) in buildings.

  • Using insecticide-coated nets to kill the mosquito and prevent them biting.

  • Preventing the mosquitos from breeding by spraying to kill the larvae or removing standing water sources.

  • Use of antimalarials when travellers visiting infected areas.