Where is Malaria most prevalent?
-Africa, Asia, Latin America
How many people are affected by malaria each year?
- 216 million ppl, 655,000 die each year
- 90% of deaths in sub-saharan africa
- 1500 cases in US each year
- one child dies from malaria each minute in Africa
What causes malaria?
- A mystery for many years!
- mal (bad) + aria (air)
- Symptom: weird recurrent fever
Alphonse Laveran:
- Examined unstained, fresh blood smears and found malarial parasite in 1880
- He found it be looking for pigment
- The infected red cell containing parasite forms and hemozoin
Ronald Ross:
-Dissected thousands of mosquitos before finding the malarial parasite in 1897 (won nobel prize in 1902)
What is important about the anopheles mosquito?
-Type of mosquito that transmits malaria!
What is the parasite inside the mosquito?
Plasmodium (Protozoa) 1-50 um in size
What might an infected malarial red cell look like?
-Contains parasite forms & hemozoin (crystals)!
What do plasmodium trophozoites look like under the microscope?
- Ring form of plasmodium
- Gray ring with red dot near the edge
What is important about Plasmodium vivax, P. ovale and P. malariae species?
- Low parasite burden
- mild anemia
- relapses (in P. vivax and P. ovale)
What is important about Plasmodium falciparum?
- High parasite burden
- Severe anemia
- Cerebral and multi-organ symptoms
- High fatality rate
What is the infective stage of malaria?
Sporozoite!
What is the life cycle of plasmodium falciparum?
- Sporozoites go into the liver/hepatic cells first
- Form hepatic schizonts
- Exoerythrocytic cycle in hepatic cells
- Burst open and release merozoites
- Merozoites go into the red blood cell, goes into the ring form, becomes trophozoite
- Forms schizont,
- Cell bursts and releases merozoites –> some are released to infect other red cells and others become macro-gametocytes that go back into mosquito form
What type of organism infects red blood cells?
Merozoites!
What is unique about the life cycle of P. falciparum?
- Trophozoites contain lots of rings!
- Gametocytes are crescent or banana-shaped gametocytes (rather than round)
What does falciparum come from?
- Falci = falx cerebri = sickle-shaped
- Parum = giving birth to
What is unique about P. malariae?
-Forms “rosette” arrangement of merozoites (in schizonts!)
What is unique about P. ovale?
- Enlarged red cells (OVAL SHAPED!) - trophozoites
- Schuffner’s dots - trophozoites
What’s unique about P. vivax?
-Enlarged red cells (schizonts) and Schuffner’s dots (trophozoites)
What is the only parasite that forms rings in RBCS?
MALARIA!!
What are schizonts called when they are released?
Merozoites!!
Why is P. falciparum worse?
- Ability to infect red cell of any age!
- Causes red cell pathology
- -“rosettes”
- -abnormal binding to endothelium
- -blood flow is impeded
- -main cause of death in children: cerebral ischemia
- Stimulates high production of cytokines
- -TNF, INF-gamma, IL-1
- -how do the bugs do that?
- -suppress red cell production, cause fever, tissue damage, and red cell binding to endothelium
What do red blood cells have in P. falciparum?
-“knobs” on RBCs that bind to ligands on vascular endothelial cells (get stuck and make clots)
What happens to the patient with malaria?
- Spleen becomes enlarged (parasites in red cells, super-active macrophages, if chronic: fibrosis, grayish color)
- Liver becomes enlarged and pigmented
- Brain vessels get plugged (red cell rosettes, hypoxia around vessels, eventually, ischemia)
- Heart, lungs may also be involved
