Malaria Pathogenesis

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Questions and Answers

The bradysporozoites in the liver spend a rest and sleeping ______ of months or even years

times

The serious complication of P.f. involves ______ malaria (involving the brain)

cerebral

Malaria caused by P.f. is more ______ than that caused by other plasmodia

severe

Relapse only occurs in ______

P.v. Signup and view all the answers

Massive haemoglobinuria (blackwater fever) in which the ______ becomes dark incolor

urine Signup and view all the answers

The mosquito bites and ______ sporozoites into the blood.

inject Signup and view all the answers

There are two forms of sporozoites: ______ and bradysporozoite.

tachysporozoite Signup and view all the answers

The process from trophozoite to merozoite is called ______.

schizogony Signup and view all the answers

The ______ stage is the diagnostic stage in human blood.

erythrocytic Signup and view all the answers

Malaria parasites such as Plasmodium falciparum infect ______ blood cells.

red Signup and view all the answers

The pathogen of malaria is _______________.

Plasmodium Signup and view all the answers

Malaria transmission will not occur at very high _______________.

altitudes Signup and view all the answers

The highest transmission of malaria is found in _______________ and in parts of Oceania such as Papua New Guinea.

Africa South of the Sahara Signup and view all the answers

Naturally acquired infections are via the bite of infected female _______________ mosquitoes.

Anopheles Signup and view all the answers

P.vivax and P.falciparum are more common species of _______________.

Plasmodium Signup and view all the answers

Plasmodium falciparum contain fine granules with ______ margins.

Maurer's Signup and view all the answers

Some Plasmodium species show ______ stippling.

basophilic Signup and view all the answers

The ring form of Plasmodium vivax has a ______ of cytoplasm.

crescent Signup and view all the answers

Plasmodium malariae has a solid ______ staining.

blue Signup and view all the answers

The trophozoite of Plasmodium falciparum has a ______ red staining nuclear dot.

brick Signup and view all the answers

Plasmodium falciparum trophozoite has a ______ form.

compact Signup and view all the answers

The infected RBC in Plasmodium malariae is ______ in size.

not enlarged Signup and view all the answers

The schizonts in Plasmodium falciparum contain ______ merozoites.

12 - 24 Signup and view all the answers

The trophozoite of Plasmodium vivax has an ______ amoeboid form.

irregular Signup and view all the answers

The infected RBC in Plasmodium ovale is ______ in shape.

oval Signup and view all the answers

Study Notes

Malaria

Malaria is caused by Plasmodium parasites, specifically P.vivax, P.falciparum, P.malariae, P.ovale, and P.knowlesi.
P.vivax and P.falciparum are more common and cause more severe infections.

Distribution

Plasmodium is widely distributed in tropical and subtropical regions of the world.
Transmission is less likely to occur in:
- Very high altitudes
- Colder seasons in some areas (P.vivax is more tolerant of lower ambient temperatures)
- Deserts (excluding oases)
- Countries with successful control/elimination programs (e.g. Western Europe and the US)
In warmer regions closer to the equator, transmission is more intense, and the highest transmission rates are found in:
- Africa South of the Sahara
- Parts of Oceania, such as Papua New Guinea

Route of Transmission

Malaria is transmitted through the bite of infected female Anopheles mosquitoes.
The parasite's life cycle involves two stages:
- Exoerythrocytic stage: Sporozoites from the mosquito bite inject into the blood and enter hepatic cells, where they multiply and form exoerythrocytic schizonts.
- Erythrocytic stage: The exoerythrocytic schizonts rupture, releasing merozoites into the blood, which then invade red blood cells and produce malaria.

Life Cycle

There are two forms of sporozoites: tachysporozoites and bradysporozoites.
Tachysporozoites grow in hepatic cells, multiply, and form exoerythrocytic schizonts, which then invade red blood cells and produce malaria.
Bradysporozoites cause relapses of malaria and stay in the hepatic cells, multiplying later.
The life cycle involves three stages:
- Exoerythrocytic stage
- Erythrocytic stage (diagnostic stage)
- Gametogenesis (formation of sexual cells, male and female gametocytes, which develop in the mosquito)

Morphology

Infected red blood cells:
- P.falciparum: Same size and shape as non-parasitized RBCs, with 6-12 coarse brick-red dots.
- P.vivax: Larger than non-parasitized RBCs, with red granules (Schuffner's dots).
- P.malariae: Same size as non-parasitized RBCs, with fine stippling (Ziemann's stippling).
- P.ovale: Enlarged and oval in shape, with fimbriated margins (Maurer's cleft) and fine stippling.
Trophozoite (ring form):
- P.falciparum: Small rings with a red staining nuclear dot and a small amount of blue-staining cytoplasm.
- P.vivax: Ring form with a nuclear dot and a crescent of cytoplasm.
- P.malariae: Ring form resembles P.vivax, but with a thicker and more intensely stained cytoplasm.
- P.ovale: Ring form with a nuclear dot and a crescent of cytoplasm.
Trophozoite (developing):
- P.falciparum: Pigments group together in a compact form, rarely amoeboid.
- P.vivax: Larger and more irregular, with an amoeboid form.
- P.malariae: Solid blue cytoplasm with a band across the RBC.
- P.ovale: Resembles P.vivax, but more compact and less amoeboid.
Schizonts:
- P.falciparum: Only present in blood in pre-terminal phase of infection, containing 12-24 merozoites.
- P.vivax: Contains 12-24 merozoites, with an enlarged infected RBC.
- P.malariae: Contains 6-12 merozoites, with an infected RBC that is not enlarged.
- P.ovale: Contains 6-12 merozoites, with an infected RBC that is enlarged and oval in shape.