Malaria (Cambridge (CIE) IGCSE Environmental Management): Revision Note

How is malaria spread?

• Malaria is a serious disease caused by a parasite called Plasmodium

  • It is not spread by dirty water itself, but by mosquitoes that breed in stagnant water

• The disease is transmitted through the bite of specific mosquitoes, making it a vector-borne disease

Female Anopheles mosquitoes as the vector

• A vector is an organism that transmits a disease from one host to another

• Malaria is spread by female Anopheles mosquitoes

  • They feed on blood to obtain protein for their eggs

Transmission from infected mosquito to human

• When an infected female Anopheles mosquito bites a human, it passes the Plasmodium parasite into the person’s bloodstream

  • The parasite travels to the liver, where it multiplies

  • It then infects red blood cells, causing symptoms such as fever, chills and fatigue

Transmission from infected human to mosquito

• If a mosquito bites a human who already has malaria, it takes in Plasmodium parasites along with the blood

  • The parasites develop inside the mosquito’s gut

• After developing, the parasites move to the mosquito’s salivary glands

  • The mosquito can now infect the next person it bites

Strategies to control malaria

• Malaria is controlled by breaking the cycle of mosquito-to-human transmission

• Strategies focus on:

  • Protecting people and preventing bites

  • Reducing mosquito populations

Personal protection

Mosquito nets

• Sleeping under insecticide-treated nets reduces bites during the night

  • Most Anopheles mosquitoes bite between dusk and dawn

Insect repellent

• Repellent applied to skin or clothing keeps mosquitoes away

  • Reduces the chance of being bitten outdoors

Vaccination

• Vaccines help the immune system recognise and fight the Plasmodium parasite

  • This can reduce the severity of malaria if someone gets infected

  • They do not give complete protection but can reduce infection rates and severe illness, especially in children

Antimalarial drugs

• Drugs that prevent parasites from multiplying in the body

  • Can be used to protect people who live in high-risk areas or those visiting high-risk areas (e.g. tourists) if taken before or during travel

Vector control

Cover or drain breeding areas

• Mosquitoes lay eggs in stagnant water, such as puddles, buckets or ponds

  • Draining or covering these areas reduces breeding

  • This can help keep population numbers under control

• Clearing blocked drains or gutters helps remove water where mosquitoes could develop

Spraying insecticides

• Large areas can be sprayed with insecticides to kill adult mosquitoes

  • This method reduces mosquito populations quickly

• Indoor residual spraying involves coating walls with insecticide

  • This method kills mosquitoes that land on surfaces

Sterilising male mosquitoes

• Releasing large numbers of sterile male mosquitoes reduces reproduction

• Females that mate with sterile males produce no offspring

• This helps reduce mosquito numbers over time

Biological control

• Introducing natural predators to eat mosquito larvae can help reduce mosquito populations

  • Fish, such as guppies, can be added to ponds or water tanks

• This method reduces mosquito populations without using chemicals