Day 11: Malaria and Microscopy Malaria Flashcards
HC 25, 26
HC25: Malaria/ Plasmodium life cycle
Sporozoites are injected by female mosquitos with blood meal
> Sporozoites go to the liver > liver stages > parasite will adapt to form for inside human host (other environment)
> In the liver, hepatocytes are infected > formation schizonts (cells with many parasite cells in it) > rupture (exo-erythrocytic cycle)
> Iron in heme from hemoglobin is needed by malaria schizonts for development: move to blood
> Erythrocyte infected: blood stages
> Immature trophozoite made (ring stage): make clones
> In erythrocytic cycle: trophozoite develops to schizont and ruptures and re-infects other erythrocytes (no recombination, asexual)
> sometimes: maturation trophozoite of the asexual stages not chosen to become gametocyte instead of mature trophozoite
> gametocytes can are taken up by mosquito and can adapt to sexual stage
Mosquito stages of Plasmodium
Gametocytes are taken up and sexual reproduction
> microgametes and macrogametes develop
> sexual recombination between one micro- and macrogamete
> reproduction to ookinetes > development to oocyst and rupture to release sporozoites
Mosquito in Plasmodium is the ..
Final host and vector
> human is intermediate host
Relevance Plasmodium
> Children susceptible
Travelers without immunity and pregnant women susceptible
Disease and high mortality: also disability and loss of economic value
Plasmodium falciparum hosts
- Heteroxenous: both human and Anopheles host (mosquito)
> intermediate host: asexual reproduction: human
> definitive host: sexual reproduction: Anopheles
Human malaria species
- Plasmodium falciparum
- Plasmodium vivac
- Plasmodium malariae
- Plasmodium ovale
- Plasmodium knowlesi (zoonosis)
» difference in morphology, although knowlesi hard to distinguish
Incubation period malaria
The hepatic stage, exo-erythrocytic cycle
> when schizonts mature until rupture
Symptoms malaria after incubation period
Flu like (aspecific) symptoms like fever, myalgia, headache
Typical malaria attacks following synchronization cycle in blood stage
Fever, anemia, enlarged spleen
Incubation period for types of malaria
vivax and ovale: 10-17 days, sometimes months to years
malariaeL 18-40 days, sometimes months to years
falciparum: 8-11 days
» can sometimes hide in liver and cause disease after being ‘cured’
Three stages of attack malaria
- Cold stage, hot stage, sweating stages
> erythrocyte ruptures, release contents and parasites, inflammation, fever peak
Infection P. vivax/ovale/malariae
Patients can be most ill but infection mostly not lethal
P. falciparum infection
Most serious disease with often lethal outcome and requires immediate treatment
> short period: organ failures
» brain, kidneys, lungs, liver, intestine
Most spread Plasmodium species
falciparum
P. vivax and P. ovale strategy
Dormancy for survival
> can make hypnozoites which can hide and survive in the liver and activate after a silent period
> after new infection with parasite (can be other malaria infection) > come into liver > old infections can re-activate
> development to more severe or milder infection (because parasite recognized earlier)
> can also re-activate without new mosquito sting
Diagnosis malaria
- direct detection parasite
- Microscopy: thin and thick smear, QBC
- Indirect detection: detection of immune responses or biomarkers with PCR, rapid tests or serology
Minimal requirements malaria
- Anopheles mosquito must be present, which are in contact with humans and in which the parasites can complete the invertebrate host part of life cycle
- Malaria parasites must be present
- Humans must be present, in contact with Anopheles mosquitos and in whom the parasites can complete the vertebrate host part of the life cycle
Prevention malaria
Interrupt one of their requirements, treating and vaccination
Quinine
Old treatment for malaria, derived from bark
> also a bit in tonic soda
> against severe malaria effective when no ACT available
> administration IV
Chloroquine
Malaria drug which is not used anymore
> it was very cheap, unfortunate
> resistance
> works against heme production so that nutrients are depleted for parasite
Sulphadoxine + Pyrimethamine
First combination therapy for malaria
> Long half life
> to fight antimicrobial resistance
> IPT for pregnant women > in all countries with high malaria prevalence, regular doses
> Also for prevention in children
> also resistance against this, so only used for prevention programs and not as treatment
Artemisinin
From a plant, which was used in tea in Asia
> Synthetic variants all derived from artemisinin, similar modes of action
> Artemisinins (an endoperoxide molecule) are activated by ferrous iron Fe2+ which creates free radicals by breaking endoperoxide ring
> endoperoxide activated by iron groups in heme to create free radicals > destroy a lot of proteins inside parasite
> parasite can adapt, by partly upregulating other proteins and bypassing: drug will work slower, parasite less sensitive
Avoiding resistance against artemisinin
Combination therapy
> with fast acting aremisia component
> long acting partner component
> combining drugs to prevent development of resistance
> parasites now need multiple routes of resistance to become insensitive
Drugs against P. vivax and ovale
- Pamaquine: prevent recurrent episodes of malarial fever
- And replaced by Primaquine: antimalarial with lower grade of toxicity
- exo-erythrocytic, because hypnozoites in liver need to be attacked
