Malaria Flashcards
Vectors
biological (more efficient) or mechanical. Many insects, esp mosquitoes. Controlling vector = controlling disease. Introducing a new vector somewhere can result in a new outbreak
How to tell which mosquito is which
Anopheles: resting position is pointing up, vector for malaria. Culex: resting position is more parallel, vector for west nile virus
Distribution of malaria
Generally closer to the equator. Some strains are resistant to certain drugs. Affects 40% of world pop, 3 million deaths/year. 90% in sub-saharan Africa.
Malaria fatalities in travellers
usually 1-5%, >20% in severe (can occur within 36-48 hours). Usually death results when people don’t recognize it’s malaria.
P faciparum
infects all RBC stages. High mortality in non immune. Cannot relapse after treatment.
P vivax
Only reticulocytes. relapses due to residual hepatic phase (an adaption for transmission in temperate climates)
Life cycle of malaria**
Sexual reproduction in mosquito. Enters human bloodstream, goes to liver, reproduces asexually and progeny infect RBC. P. falciparum infects young and old RBC and causes lysis with its asexual reproduction (note there is no liver stage after this). P vivax infects young RBC (reticulocytes) and because it has a hypnozoite liver phase after the RBC phase (falciparum does NOT have this stage), relapses are possible after weeks/months symptom free.
Genetic immunity to malaria
People with sickle cell anemia are less likely to get malaria. Thallasemia diseases and G6PD deficiency are also protective
Malaria in pregnancy
Usually fatal to fetus. Parasite evade immune system in placenta. AB transfered to child (if it survives) only last so long too.
Categories of malaria vaccine
Classify by parasite stages that are targeted: 1. pre-erythrocytic. 2. asexual blood stages. 3. mosquito stages
Clinical effects of malaria
Asymptomatic or intermittently symptomatic in “immune” hosts. Febrile illness with temporary disability. Anemia, multiple mechanisms. Adverse pregnancy outcomes. Effects on other diseases (Burkitt’s lymphoma, HIV). *Organ failure b/c RBC get stuck (brain, kidney, lung etc.). *mortality 20% in severe malaria, even with optimal treatment. *Death (stars indicate falciparum)
Common symptoms
Fever, chills, sweats, headaches, nausea, vomiting, malaise. Fairly non-specific, can be confused for other things.
Severe malaria
Caused by P falciparum. Can cause RBCs to stick to endothelium, block small vessels, and cause organ damage. Life-threatening!
Diagnosing malaria
Travel Hx! Lots of non specific symptoms, fever, spelenomegaly, thrombocytopenia. Look under microscope at blood smear. Hematuria, signs of anemia or hemolysis. PCR
How to treat malaria
If unsure which species, assume the worst! Treat with atovaquone proguanil or if the symptoms are severe (unconscious, severe anemia, kidney failure, respiratory distress, acidosis, seizures, parasitemia >5%), use artesunate or quinine. For P. vivax, do follow up therapy with primaquine for hypnozoite stage
