Is malaria a protist?

AQA's GCSE Biology specification uses malaria as its example of a protist disease: malaria is caused by a protist, the malarial protist has a life cycle that includes the mosquito, and the disease causes recurrent episodes of fever and can be fatal.

What is a protist?

Protists are a varied group of mostly single-celled organisms with a nucleus, so they are eukaryotes, like plant and animal cells, not prokaryotes like bacteria. They don't fit into the plant, animal or fungus kingdoms. Some, like algae, photosynthesise. Others, like amoebas, feed on other organisms. A few are parasites that cause disease, and Plasmodium is the most important of these.

How is malaria spread?

Malaria spreads mainly through the bites of infected female Anopheles mosquitoes, according to the World Health Organization. The mosquito is a vector: an organism that carries a pathogen from one host to another without getting the disease itself. Only female mosquitoes bite, because they need blood to develop their eggs. Much more rarely, malaria can also pass on through blood transfusions and shared needles.

The malaria life cycle

1. An infected mosquito bites a person and injects Plasmodium along with its saliva.
2. The parasites travel in the blood to the liver, where they multiply.
3. They then invade red blood cells, multiply again and burst out, destroying the cells. Each burst releases more parasites, which infect more red blood cells. These cycles cause the repeated bouts of fever.
4. Some parasites develop into forms that a mosquito picks up when it bites the infected person.
5. Inside the mosquito, the parasites reproduce and move to its salivary glands, ready to infect the next person it bites.

So the protist needs both hosts, human and mosquito, to complete its life cycle. That is why controlling mosquitoes controls malaria.

Symptoms of malaria

Symptoms usually start 10 to 15 days after an infected bite, the WHO says, and early ones include fever, headache and chills, which can be mild and hard to recognise. Without treatment, the most dangerous species, P. falciparum, can become severe and cause death within 24 hours.

How serious is malaria?

Very. The WHO estimates there were 282 million malaria cases and 610,000 malaria deaths worldwide in 2024. About 95% of both were in the WHO African Region, and children under 5 accounted for about 75% of malaria deaths there. Five species of Plasmodium infect humans. P. falciparum is the deadliest and most common in Africa, and P. vivax is the most common in most countries outside sub-Saharan Africa.

How is malaria controlled?

Because the protist needs the mosquito, most control targets the vector. AQA's specification names two key methods: stopping mosquitoes from breeding, and using mosquito nets to avoid being bitten.

• Insecticide-treated bed nets: Anopheles mosquitoes often bite at night, so sleeping under a treated net protects people and kills mosquitoes.
• Removing breeding sites: mosquito larvae develop in still water, so draining it or treating it with insecticide cuts mosquito numbers.
• Indoor spraying: insecticide on the inside walls of homes kills mosquitoes that rest there.
• Antimalarial drugs: to treat infected people quickly, which also stops mosquitoes picking up the parasite from them, and to protect travellers.
• Vaccines: the WHO recommends two malaria vaccines for young children in areas with moderate to high transmission, RTS,S and, since October 2023, R21. They are now being rolled out across Africa.

Exam tips

• Name the right things: the pathogen is a protist (Plasmodium), the vector is the mosquito, and the symptom AQA names is recurrent fever.
• Don't call the mosquito the pathogen. It carries the protist but doesn't cause the disease itself.
• Link control to the life cycle: nets and stopping breeding work because the protist must pass through mosquitoes.
• Malaria isn't spread person to person directly, through coughs or touch, so isolating patients isn't the main control method.

Our Human Physiology course covers how the body defends itself against pathogens, and our guide to antibodies explains how the immune system fights them. Daily GCSE Biology Higher papers give short timed practice on questions like these.

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