Malaria

• Caused by Plasmodium spp.– Protist

• Female Anopheles mosquito feed on human blood and acts as a ‘vector’ for the parasite– Transfers it between humans

• May also be transferred by:– Blood transfusions– Unsterile needles– Across the placenta from mother to a foetus

Plasmodium life cycle

• Mosquito takes up some of the parasite’s gametes from an infected person

• Pass into the next human with anti-coagulant in saliva of mosquito

• Enters red blood cells of human• Multiplies in human and in mosquito

Life Cycle Plasmodium

Infected Red Blood Cells

Features of Malaria

Occurence

Immunity

• May become immune if continually reinfected– Have to survive first five years of infection

• Epidemics where malaria is not endemic are very dangerous– And where outbreaks after the rainy season

Controlling Malaria

1. Reduce number of mosquitoes

2. Avoid being bitten

3. Drugs to prevent the parasite infecting people

Kill Mosquitoes• Spread oil on water which mosquitoes breed in

– Prevents larvae from getting oxygen from the surface

• Drain marshes• Add fish which eat mosquito larvae to ponds etc.• Spray with bacterium which kills mosquito larvae

Avoid being bitten

• Nets

• Insect repellent

• Soak nets in insecticide

• Cover skin at dusk

• Sleep with a dog or a pig!

Drugs

• Treat infected people and as prophylactic (preventative)

• Quinine• Chloroquine

– Prevents parasite spreading by inhibiting protein synthesis

• Plasmodium may develop resistance– Eg widespread chloroquine resistance– Use Mefloquine instead, but:

• Expensive & side effects: dizziness, vomiting, disturbed sleep

At Risk

• Visitors to countries

• Misdiagnosed in other countries (‘flu)

• Immigrants who visit relatives– Immunity is lost

Eradication Attempt

• 1950’s, World Health Organisation• Unsuccessful, because:

– Resistance by Plasmodium– Resistance by mosquitoes (eg to DDT)

• Immunity lost and resulted in deaths when the disease returned

• Expensive• Insecticides killed wasps which ate caterpillars

which eat thatched roofs• Programme did not involve indigenous people

Concern

• Increase in resistance of Plasmodium

• Increase in worst species, P. falciparum

• Climate change favours outbreaks

• Increased migration (due to wars)

• No vaccine available

• One of world’s biggest health threats

Progress….

• Improve diagnosis eg ‘dipstick’ test

• Supply effective drugs– Eg Genome sequencing

of plasmodium to find vaccine

• Use drug combos to reduce resistance

• Prevent transmission