Vector and Fluid-borne Pathogens: Malaria and Ebola

Worked Example: Explaining Malaria Prevention

Explain how the use of insecticide-treated mosquito nets can reduce the spread of malaria. (3 marks)

Step 1: Identify the role of the insect.

• Mosquitoes act as vectors that carry the malarial protist.

Step 2: Explain the physical mechanism.

• The nets provide a physical barrier that prevents the mosquito from biting humans, while the insecticide kills any mosquitoes that land on it.

Step 3: Link back to the transmission cycle.

• Because the mosquito cannot bite, the protist cannot be injected into the human's bloodstream, breaking the chain of infection.

Ebola: Pathogen and Transmission

• Unlike airborne diseases that spread easily through coughs and sneezes, some viruses require a much closer physical exchange to infect a new host.
• Ebola is caused by the Ebola virus and is spread through direct contact with infected body fluids.
• These infectious fluids include blood, vomit, faeces, saliva, sweat, and semen from an infected person or animal.
• The virus enters a new host through broken skin or mucous membranes (such as the eyes, nose, or mouth).
• It can also survive for several days on contaminated objects (like bedding or medical needles), meaning physical contact with these items can cause infection.

The Mechanism of Ebola Infection

• Once inside the human body, the Ebola virus targets and destroys liver cells, white blood cells, and the cells lining blood vessels.
• It reproduces using the lytic cycle, where the virus replicates rapidly inside host cells until they burst open.
• The severe destruction of blood vessel linings leads to haemorrhagic fever, characterised by massive internal and external bleeding, alongside a high temperature and severe vomiting.

Preventing the Spread of Ebola

• Because there is a high risk of transmission from fluids, preventing Ebola requires strict hygiene protocols.
• Isolation: Infected patients must be quarantined (physically separated) from healthy individuals to prevent any direct contact with their fluids.
• Sterilisation: Areas, surfaces, and medical equipment must be rigorously cleaned using high temperatures or strong disinfectants (like bleach) to destroy the virus.
• Personal Protective Equipment (PPE): Medical staff must wear full-body protective clothing—including gloves, gowns, masks, and goggles—to create a complete, impermeable barrier against fluid transfer.
• Safe burial: The virus remains highly active even after a patient has died, so deceased victims must be handled with extreme care to prevent contact with infectious remains.