(11) Example of a protist pathogen communicable diseases

Malaria is caused by a protist (a type of unicellular eukaryote cell).

Malaria causes damage to red blood cells and in severe cases, the liver.

Malaria causes repeated episodes of fever which can overwhelm the bodies defences and prove fatal.

The symptoms of malaria include fever (raised temperature above normal), sweats and chills, headaches, muscle pain, diarrhoea and a cough.

Part of the malarial protist's life cycle is inside an animal - including us!

The mosquito is an animal vector - a 'carrier' - a means of spreading a disease - it conveys the protist without any ill-effect to itself - it just passes the protist on without developing the disease!

In this case the mosquito insect is the animal vector.

The female mosquito feeds by sucking blood from warm-blooded animals - if the animal is infected with malaria, the protist is spread when the same mosquito feeds on another animal.

When the mosquito does feed on another animal, it infects it by inadvertently passing the malarial protist into the blood stream when feeding - the mosquito's mouthparts are adapted to break through skin and suck out blood, but the act of feeding inserts the malaria protist at the same time.

Malaria is still a common infection in many parts of the world but you can do some things to combat it.

The mosquito's life cycle is complicated.

Mosquitoes breed on standing water where the eggs hatch and the larvae develop into pupas in the water.

You can reduce the spread of malaria by stopping the mosquitoes from breeding e.g. affecting their breeding grounds by draining swamps in various ways e.g.

You can spray swamps with insecticide (biodegradable I hope).

You can spray oil on the water to stop the larvae breathing.

As a precaution, people living in areas with malaria risk should make sure any containers of standing water from rain are got rid of to minimise risk of mosquitoes breeding on the surface of the water.

For your own personal protection strategies from insect bites and reduce the chance of spreading malarial disease you can ...

(i) use insecticide sprays to kill the mosquitoes,

(ii) treat any exposed skin with insect repellent,

(iii) employ mosquito nets over your bed at night to stop getting bitten while sleeping,

 - all of which are designed to stop mosquitoes biting you and passing the malaria disease on!

If infected, you can take an antimalarial drugs to kill the specific harmful protist in your bloodstream.

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Key points Source of information is based on textbooks & syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Key points about malaria

Revision notes on protist pathogen communicable diseases.

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Protist Pathogen Disease: Malaria

1. What Are Protists?

• Protists are eukaryotic, mostly single-celled organisms.

• Some are pathogenic, meaning they cause disease.

• Unlike bacteria and viruses, protists often have complex life cycles and may require a vector to spread.

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2. What Is Malaria?

• Malaria is a communicable disease caused by a protist pathogen from the Plasmodium genus.

• It is transmitted to humans by the female Anopheles mosquito, which acts as a vector.

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3. Transmission of Malaria

• When an infected mosquito bites a person, it injects the Plasmodium protist into the bloodstream.

• The protist travels to the liver, multiplies, and then infects red blood cells.

• When red blood cells burst, the protists are released, causing symptoms and allowing further spread.

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4. Symptoms of Malaria

• Recurrent fever (comes and goes in cycles)

• Chills and sweating

• Headaches

• Muscle aches

• Vomiting and diarrhoea

• In severe cases: organ failure, coma, or death

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5. Effects on the Body

• Destroys red blood cells, leading to anaemia

• Damages the liver and kidneys

• Weakens the immune system

• Can be fatal, especially in young children and pregnant women

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6. Treatment of Malaria

• Antimalarial drugs (e.g. chloroquine, artemisinin-based combination therapies)

• Treatment depends on:

  • The Plasmodium species

  • Drug resistance in the region

  • Severity of symptoms

• Early diagnosis is crucial for effective treatment

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7. Prevention of Malaria

• Insecticide-treated mosquito nets (ITNs) – prevent bites during sleep

• Insect repellents and protective clothing

• Draining standing water – reduces mosquito breeding

• Indoor spraying with insecticides

• Antimalarial tablets for travellers

• Vaccination – a malaria vaccine (e.g. RTS,S) is now available in some countries

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Why Is This Important in Human Biology?

• Demonstrates how protists differ from bacteria and viruses

• Highlights the role of vectors in disease transmission

• Reinforces the importance of public health strategies in disease control

• Links to immune response, global health, and epidemiology

• Encourages understanding of preventative medicine and drug resistance

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Quick Summary Table

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Keywords, phrases and learning objectives for this part on malaria

Know that malaria is an example of a protist pathogen communicable disease.

Be able to understand the life cycle of the mosquito insect in terms of a vector.

Know the malaria infection symptoms e.g. fever, how malaria infection can be treated, methods of protection and strategies to avoid mosquito bites.

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