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44 Cards in this Set

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What are protozoas?
-Single celled organisms
-Move by a variety of forms
-Amoebas move by throwing pieces of cytoplasm into the environment
-Some have flagella
-Sometimes they follow gradients of nutrients or chemical trails to an organism
What are the important malarias in humans?
Plasmodium falciparum (most deadly)
Plasmodium vivax
Plasmodium malariae
Plasmodium ovale
What makes a person more susceptible to malaria?
Having their spleen removed
Where is Plasmodium falciparum found?
Tropical regions of the world: SubSaharian Africa, India, SE Asia, parts of South America
Where is Plasmodium vivax found?
East Africa, Parts of South America, India, SE Asia
Where is Plasmodium ovale found?
West Africa
Describe most people who die from malaria
Children living in Sub-Saharian Africa.
What is the relationship between malaria outbreaks and water?
-Malaria is transmitted by mosquitoes
-In droughts malaria does not spread because the mosquitoes cant breed.
Why is malaria a problem in SubSaharian Africa?
There are alot of river systems that have been damed up and there is alot of irrigation. A lot of people are near water.
Describe what mosquitoes do with blood?
-Female mosquitoes suck blood
-The serum goes through the mosquito and the RBCs are collected
-Proteins from RBCs used to make eggs
-Eggs are released 1 week after the blood meal
Describe the world situation with regards to malaria
-Approx. 2 billion infections/yr
-Economic and social development reduced
-27% of the world lies within the malaria transmission zone
-New unstable transmission area: Bangladesh
What is the definitive host for malaria?
Mosquito
What does the definitive host do?
Hosts the sexual stages
Describe malaria in people
Malaria is an intracellular parasite living in RBCs only
How do you differentiate malaria strains in a human infection?
By the morphology of the infected RBC
Describe the life cycle of Plasmodium falciparum
-Begins with the bite of an infected mosquito
-Mosquito bites, transmitting sporozoite stage
-Sporozoites disseminate
-Encounters receptors on the sinusoids of the liver that allow for production of blood proteins
-Attach and actively penetrate the vessel until they encounter the parenchymal cell
-Reproduces in the parenchymal cell, producing haploids
-After a week it goes from cryptozoite to merozoite (still a haploid)
-Merozoite distributed throughout body
-Encounters RBCs
-Recognized by certain RBC receptors
-RBC membrane invaginates and creates a vacuole
-Feeds on Hb
-Transduces a signal on the RBC that causes it to stick to endothelial cells
-Sticks to precapillaries and lowers blood O2 tension
-RBCs fill with parasite and it infects more RBCs
-Differentiates into either macrogametocyte and microgametocyte.
-Produces presexual infectious stages in circulating blood
-Mosquito bites and acquires these stages
How are malaria infections transmitted?
Horizontally, not vertically
How many mosquitoes take 2 blood meals before dying?
~1%
Describe the sporozoite stage of Plasmodium falciparum
Haploid
Describe the life cycle of Plasmodium falciparum in the mosquito
-The two presexual stages are released from the membrane of the RBC on which they sdie by digestive juices of the mosquito's stomach
-Parasite differentiates into makes and females
-Males produce sperm and fertilize females
-Female produces a zygote
-Zugoe micrigrates through cell conntections of stomach and resides in some membrane
-Develops into an oocyst
-Oocyst produces sprozoites
-Organism goes froma diploid to a haploid
-Sporozoite is infectious to humans
-Sporozoite enters hemalymph of mosquito
-Sporozoite ends up in the salivary glands of the female
How are mosquitoes attracted to humans?
-Chemical signature (odor)
-CO2
-Body Heat
Ex-flagellation of the microgametocyte of a malaria parasite in mosquito stomach
Exo-erythrocytic stages of malaria in liver parenchymal cell
Merozoite entering a red cell
Describe the erythrocytic stages of malaria
-They all begin with a ring stage
-They then differentiate based on species
-3-5 days to complete a round of infection in a given red cell
Describe the Pathogenesis of malaria
-Anemia
-Liberation of material from RBCs includes cellular material and parasite waste products
-Those products elicit fever every time a cycle occurs in RBCs
-Immune system kicks in
-Spleen enlarges but liver stays the same size
-Spleen can rupture in first time malaria patient
-Classic signs include chills, fever, sweats
-Chills are from lack of O2
-Fever is due to pyogenic material
-Sweats are from diminishing pyogenic effects and fever.
-Feel good after sweats but then the whole cycle starts again
-Symptoms more pronounced with each round
What causes cerebral malaria? Describe cerebral malaria
P. falciparum only
. It is the one that sticks inside the precapillary vessels and lowers the oxygen. It induces TNF on the brain side of the tissue. TNF results in NO production. When you are exposed to NO you go to sleep. You can go into a coma. Cerebral malaria can lead ot a coma and if untreated patients die. Metabolic acidosis is a hallmark for cerebral malaria.
What are the long term effects of repeated malaria infection?
-Learning deficit
-Reduced growth rate
-Spontaneous abortion
-All may be due to prolonged metabolic acidosis
What are the clinical signs and symptoms of malaria?
-Fever, paroxysms of shaking chills
-Tertian vs quartan fever pattern
-Symptoms when other organs involved
-Hemolysis: icterus, jaundice, enlarged spleen
-Cognitive deficit over time

-Antigenic changes prevent memory immune attack
What pathogenesis is limited to P. falciparum?
-Cerebral malaria
-Retinopathy
What is unique to the P.vivax life cycle?
-Some sporozoites get into the liver and dont reproduce
-This is the hypozoite stage
-The parasite sits and waits
-This causes relapsing malaria
-Can lie in wait up to 5 years
-Must cure liver stages if you want to fully cure disease
When does most death from malaria occur?
Between 8 months and 5 years of age
EM of RBC infected with P. falciparum. Surface has little histadine rich nobs that it uses to attach to the surface of endothelial cells
This is a monkey with cerebral malaria from P. falciparum. The parasite is inside the vessel in the precapillary area.
How do you diagnose malaria?
-Blood smear
-Stain
-Look under microscope
-Look every 6 hours for malaria
-Treat for 3 days

-Can also detect by circulating antibodies
-We can create a buffy coat by centrifuging blood and then looking for malaria pigment in the neutrophils.
What does the treatment depend on?
-Type of malaria
-Knowledge of regional resistance
-Severity of illness (oral vs IV)
-Age of patient
Where is drug resistance malaria located?
Africa, S. Amoeria, China and South Asia, SE Asia
Why is P. falciparum the strain with the most resistance?
It grows faster thus develops resistance faster
What is the parent compound for most antimalarial drugs?
Quinine
Esp. good against P. falciparum
Describe chloriquine
It is an older quinine derivative to which there is must resistance
Describe mefloquine
It is a newer quinine derivative used for resistance strains of P. falciparum
What are the current drugs of choice for malaria?
Atovoquan
Proguanil
Describe antifolate treatment
Sulfonamides/Dapsone inhibits Dihydropteroate Synthetase

Pyrimethamine/Proguanil inhibits Dihydrofolate reductase
Describe antimalarial prophylaxis
-NA travelers lack immunity to malaria
-Risk of acquiring malaria depends on rural travel, altitude, season of travel
-Highest risk of low lying areas during rainy seasons
-Personal protection measures against mosquitoes are important as drugs
-Insect repellants, mosquito nets, clothing covering body
-Antimalarial drugs do not prevent infection and initial liver stage