Malaria:
➡ Protozoal disease transmitted by female Anopheles mosquitoes.
➡ Caused by the Plasmodium protozoan genus.
➡ Four species affecting humans:
➡ P. falciparum: Malignant malaria (most fatal)
➡ P. vivax: Tertian malaria
➡ P. ovale: Tertian malaria
➡ P. malariae: Quartan malaria
➡ Falciparum malaria is responsible for most deaths.
Transmission:
➡ Transmitted via female Anopheles mosquito bites or blood inoculation.
➡ Female mosquitoes carry Plasmodium parasites and transmit them during
blood meals.
➡ High environmental temperature and stagnant water create ideal mosquito
breeding conditions.
➡ Common in lowlands during the rainy season.
➡ Rare congenital transmission cases known.
Life Cycle:
Plasmodium has a two-part life cycle: asexual and sexual phases.
➡ Asexual Cycle (Human):
➡ Liver Phase: Sporozoites injected by female Anopheles mosquitoes
infect liver cells and multiply, producing thousands of merozoites.
➡ Erythrocytic Phase: Merozoites invade red blood cells (RBCs),
multiply, and rupture RBCs every 48-72 hours. Symptomatic stage begins.
➡ In P. vivax and P. ovale, some liver forms remain dormant as
hypnozoites, causing relapses.
➡ Sexual Cycle (Mosquito):
➡ Occurs inside female Anopheles mosquitoes (definitive host).
, ➡ Male and female gametocytes ingested during mosquito blood
meal.
➡ Gametocytes form zygotes, mature into ookinetes in the mosquito's
midgut, develop into oocysts, and release sporozoites.
Pathogenesis
Liver Phase: Sporozoites invade liver cells, multiply, and release merozoites.
➡ Erythrocytic Phase:
➡ Merozoites invade RBCs, enlarge into trophozoites, develop
pigment, and multiply.
➡ Trophozoites become amoeboid, consume hemoglobin, and develop
into schizonts.
➡ Schizonts release multiple merozoites, which infect new RBCs.
➡ Destruction of RBCs leads to anemia.
➡ Infected RBCs and sometimes uninfected ones are cleared by the
spleen, leading to splenomegaly.
➡ P. falciparum-infected RBCs adhere to blood vessel walls
(cytoadherence) and to uninfected RBCs, leading to RBC sequestration in
vital organs.
➡ This contributes to disease severity and makes detection of mature
forms difficult in P. falciparum.
➡ Gametocyte Formation: After several asexual cycles, some parasites
develop into sexual forms (gametocytes) that can transmit malaria.
➡ Female mosquitoes ingest gametocytes during blood meals.
➡ In the mosquito, gametocytes form zygotes, mature into ookinetes,
develop into oocysts, and release sporozoites.
Clinical Features of Malaria:
➡ Incubation Period:
➡ P. vivax, P. ovale, and P. falciparum: 10-14 days
➡ P. malariae: 18 days to six weeks
➡ Protozoal disease transmitted by female Anopheles mosquitoes.
➡ Caused by the Plasmodium protozoan genus.
➡ Four species affecting humans:
➡ P. falciparum: Malignant malaria (most fatal)
➡ P. vivax: Tertian malaria
➡ P. ovale: Tertian malaria
➡ P. malariae: Quartan malaria
➡ Falciparum malaria is responsible for most deaths.
Transmission:
➡ Transmitted via female Anopheles mosquito bites or blood inoculation.
➡ Female mosquitoes carry Plasmodium parasites and transmit them during
blood meals.
➡ High environmental temperature and stagnant water create ideal mosquito
breeding conditions.
➡ Common in lowlands during the rainy season.
➡ Rare congenital transmission cases known.
Life Cycle:
Plasmodium has a two-part life cycle: asexual and sexual phases.
➡ Asexual Cycle (Human):
➡ Liver Phase: Sporozoites injected by female Anopheles mosquitoes
infect liver cells and multiply, producing thousands of merozoites.
➡ Erythrocytic Phase: Merozoites invade red blood cells (RBCs),
multiply, and rupture RBCs every 48-72 hours. Symptomatic stage begins.
➡ In P. vivax and P. ovale, some liver forms remain dormant as
hypnozoites, causing relapses.
➡ Sexual Cycle (Mosquito):
➡ Occurs inside female Anopheles mosquitoes (definitive host).
, ➡ Male and female gametocytes ingested during mosquito blood
meal.
➡ Gametocytes form zygotes, mature into ookinetes in the mosquito's
midgut, develop into oocysts, and release sporozoites.
Pathogenesis
Liver Phase: Sporozoites invade liver cells, multiply, and release merozoites.
➡ Erythrocytic Phase:
➡ Merozoites invade RBCs, enlarge into trophozoites, develop
pigment, and multiply.
➡ Trophozoites become amoeboid, consume hemoglobin, and develop
into schizonts.
➡ Schizonts release multiple merozoites, which infect new RBCs.
➡ Destruction of RBCs leads to anemia.
➡ Infected RBCs and sometimes uninfected ones are cleared by the
spleen, leading to splenomegaly.
➡ P. falciparum-infected RBCs adhere to blood vessel walls
(cytoadherence) and to uninfected RBCs, leading to RBC sequestration in
vital organs.
➡ This contributes to disease severity and makes detection of mature
forms difficult in P. falciparum.
➡ Gametocyte Formation: After several asexual cycles, some parasites
develop into sexual forms (gametocytes) that can transmit malaria.
➡ Female mosquitoes ingest gametocytes during blood meals.
➡ In the mosquito, gametocytes form zygotes, mature into ookinetes,
develop into oocysts, and release sporozoites.
Clinical Features of Malaria:
➡ Incubation Period:
➡ P. vivax, P. ovale, and P. falciparum: 10-14 days
➡ P. malariae: 18 days to six weeks
