GradeGen.AI

Malaria: The Pathogen and Its Vector

Every time you get an itchy mosquito bite, it is usually just a minor annoyance. However, in many parts of the world, mosquitoes carry deadly pathogens.
Malaria is a communicable disease caused by a protist (a type of eukaryotic microorganism) from the genus Plasmodium.
The disease is spread by female Anopheles mosquitoes, which act as an animal vector.
An animal vector carries the pathogen and passes it from one host to another, but it does not suffer from the disease itself.

The Malaria Transmission Cycle

To understand how to stop malaria, we must first look at the transmission of the protist through its lifecycle.
An infected mosquito bites a human and injects the Plasmodium protist into their bloodstream via its saliva.
The protists travel directly to the human liver, where they multiply asexually.
They then enter red blood cells, continuing to multiply until the cells burst (lyse), releasing more protists and toxins.
This bursting of red blood cells causes severe symptoms, including recurrent fever, chills, and fatigue.
If a healthy mosquito bites this infected person, it ingests the protists, which then reproduce sexually inside the mosquito before migrating to its salivary glands.

Preventing the Spread of Malaria

Because mosquitoes are the vectors, preventing malaria relies heavily on disrupting their lifecycle or stopping them from biting humans.
Stop breeding: Mosquitoes lay their eggs in stagnant, standing water (such as puddles or old tyres). Draining these water sources prevents them from reproducing.
Kill the vectors: Insecticides can be sprayed inside homes on resting walls to kill adult mosquitoes. Spreading a thin layer of oil or detergent on standing water stops larvae from breathing.
Biological control: Introducing specific predatory fish into ponds can naturally reduce the mosquito larvae population.

Students often state that the mosquito is the pathogen that causes malaria. The mosquito is actually the animal vector; the true pathogen is the Plasmodium protist.

In 'Explain' questions about malaria transmission, examiners specifically look for mentions of the protist replicating in the human liver and bursting red blood cells.

When asked how to prevent the spread of Ebola, always prioritise isolation of patients and sterilisation of areas, as these are frequently the top two marks on Edexcel mark schemes.

Do not confuse Ebola with airborne diseases; Edexcel mark schemes strictly require you to state it is transmitted via body fluids, so wearing a standard surgical mask is not enough without full PPE.

A disease that can be spread from one person or organism to another.

A diverse group of eukaryotic microorganisms, many of which are parasites that require a host to survive.

An animal that carries a pathogen from one host to another without being affected by the disease itself.

The process by which a pathogen is passed from an infected host to a susceptible individual.

Physical touching or exchange of fluids between an infected host and a susceptible individual.

Liquids originating from inside the bodies of living people, such as blood, vomit, or saliva, which can act as a medium for pathogen transmission.

A severe viral illness characterised by internal and external bleeding, caused by the destruction of blood vessel linings.

The complete physical separation of infected patients from healthy individuals to prevent further transmission.

The process of making an object or area entirely free from all living microorganisms and viruses.

Specialised clothing or equipment, such as gloves, gowns, and goggles, worn to create a physical barrier against infectious materials.