Malaria (Cambridge International IGCSE Environmental Management)

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

Infected mosquitos can transmit malaria when they bite human skin (Dunpharlain, CC BY-SA 4.0, via Wikimedia Commons)

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

Exam Hint Students often think, 'mosquitoes cause malaria,' but examiners want the wording that mosquitoes are just the vectors that carry the Plasmodium parasite. This distinction is crucial.

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

Exam Hint Combining multiple methods (personal protection and vector control) gives the strongest protection—you may be able to gain extra marks in some exam questions for stating this.