Transcript Plasmodium spp.

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
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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