Lecture notes Biodiversity: Exploiters and Exploited Malaria (BI2EEE4)

22.10.19

L4 – Malaria
Keywords:
Quartan fever, cyclical fever, polymorphic (multiple life stages)

Lecture:
 Claims 1mil lives
 Parasite (Plasmodium) – Protozoan (Euk)
 Members of phylum = all intracellular parasites
o Main – P. vivax (Europe), P. falciparum (90% deaths – not well adapted to humans
so always kills instead of keeping hosts), P. ovale and P. malariaae (rare), P. knowlesi
(monkey malaria – evolving to human
malaria)
o Lifecycle:
 10 lifecycle phases
 In mosquito (sexual repo)
 Replication 1 – amplification
(mitosis)
 Gametocytes
o Macrogametocytes =
female (not broken
down)
o Microgametocytes = male (not broken down by mosquito)
o Ingested and egg/sperm fuse in mosquito gut to form zygote
 Diploid zygote performs meiosis to form haploid
ookinete cells
 The cells form oocysts (seen on EM) – amplification
 Cyst bursts to release sporozoites and then they
travel to salivary glands (w/anaesthetic) to pass
onto next host
 Sporozoite injected by mosquito -blood/lymphatics→ liver
 Merozoites and RBCs broken down
 Takes 2 weeks for readministration/reinfection of mosquito (gets
colder = stops)
 In human liver
 Replication 2 – amplification (merozoites released to RBCs)
 Sporozoite becomes a less invasive hepatic trophozoite cell
 Sporozoite’s infect cell to become a hepatic schizont cell
 Merozoites (1.2um) released into blood
o P. vivax and P. ovale have resting periods in liver as
hypnozoites
 In human RBC
 Amplification in RBC
 Merozoite becomes trophozoite or gametocytes (ingested→repo)
 Merozoites make pocket in RBC and feed on Hb in RBC
 Granules on outside of RBCs = falciparum waste
 Gets cells stuck in caps so that not consumed by liver

, 22.10.19

 16 new merozoites in RBC and bursts
 Infection builds up (synchronized bursting = fevers)
o Staining RBCs show merozoites stages in the RBC
 Mosquito (Anopheles)
o Female (suck blood), Anopheles genus = transmitting vector
 5 bites required to ensure infection
o Lifecycle
 Blood meal from host to rear batches of eggs
 Rest and digest meal to mature eggs
 Lays 50-150 eggs in water and hatch in 2-3 days
 Larval stages in top of water (at an angle flat to surface)
 Pupates in water with breathing tube
 Leaves water when adult (3 days after hatching)
o Unknown how many species (morph similar but behaviour/requirements different)
 Malaria effects
o 2018
 435,000 deaths/year (61% < 5 years old bc ↓ innate immunity)
 Young adult in malaria area = infect/survive bc repeated infection
o Lost immunity by leaving malaria area/when pregnant
 3.4 billion people at risk of malaria
 Malaria symptoms
o After synchronised bursting of RBCs
o Stage 1 = headache, cold, shivering
o Stage 2 (1 hour later) = 41֯C w/↑ sweating
o Stage 3 (8-9 hours later) = normal temp but exhausted
o P vivax and P. ovale = cyclical fever 1 day of fever and 3 days off
 P vivax = anaemia, lung issues and rarely coma
 ↑∆ relapse bc fast production of sporozoites in mosquitoes at low
temps
o P. malariae = quartan fever 1 day on and 1 day off
 Causes kidney disease (occurs decades later if in resting phase)
o P. falcipaeum = cyclical fever w/ coma, fits and death
 Bc ↑# of infected RBCs
 Sequestration
 Endemic to Saharan Africa (natural immunity – breast milk?)
 Natural immunity for being infected for 10-15 years 5x/year
 Immunosuppression in preg = ↑ susceptibility
 Malaria control
o Move out of malaria areas (low-lying areas/Southern lowlands were infected in
summer, two house – one for winter too)
o Quinine
 Bark of cinchona tree
 South America/Andes (high humidity and altitude)
 Discovered in 1632 (locals used beforehand)
 Reduce symptoms and kill blood stage of bacterium
 Europeans introduced malaria as not native to SA looking for malaria cure
 Dried samples sent back and ground up bark = Jesuit’s powder