Parasitology 05 Intro. To Protozoa; Malaria

Front 1

What are protozoas?

Back 1

-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

Front 2

What are the important malarias in humans?

Back 2

Plasmodium falciparum (most deadly)
Plasmodium vivax
Plasmodium malariae
Plasmodium ovale

Front 3

What makes a person more susceptible to malaria?

Back 3

Having their spleen removed

Front 4

Where is Plasmodium falciparum found?

Back 4

Tropical regions of the world: SubSaharian Africa, India, SE Asia, parts of South America

Front 5

Where is Plasmodium vivax found?

Back 5

East Africa, Parts of South America, India, SE Asia

Front 6

Where is Plasmodium ovale found?

Back 6

West Africa

Front 7

Describe most people who die from malaria

Back 7

Children living in Sub-Saharian Africa.

Front 8

What is the relationship between malaria outbreaks and water?

Back 8

-Malaria is transmitted by mosquitoes
-In droughts malaria does not spread because the mosquitoes cant breed.

Front 9

Why is malaria a problem in SubSaharian Africa?

Back 9

There are alot of river systems that have been damed up and there is alot of irrigation. A lot of people are near water.

Front 10

Describe what mosquitoes do with blood?

Back 10

-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

Front 11

Describe the world situation with regards to malaria

Back 11

-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

Front 12

What is the definitive host for malaria?

Back 12

Mosquito

Front 13

What does the definitive host do?

Back 13

Hosts the sexual stages

Front 14

Describe malaria in people

Back 14

Malaria is an intracellular parasite living in RBCs only

Front 15

How do you differentiate malaria strains in a human infection?

Back 15

By the morphology of the infected RBC

Front 16

Describe the life cycle of Plasmodium falciparum

Back 16

-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

Front 17

How are malaria infections transmitted?

Back 17

Horizontally, not vertically

Front 18

How many mosquitoes take 2 blood meals before dying?

Back 18

~1%

Front 19

Describe the sporozoite stage of Plasmodium falciparum

Back 19

Haploid

Front 20

Describe the life cycle of Plasmodium falciparum in the mosquito

Back 20

-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

Front 21

How are mosquitoes attracted to humans?

Back 21

-Chemical signature (odor)
-CO2
-Body Heat

Front 22

Back 22

Ex-flagellation of the microgametocyte of a malaria parasite in mosquito stomach

Front 23

Back 23

Exo-erythrocytic stages of malaria in liver parenchymal cell

Front 24

Back 24

Merozoite entering a red cell

Front 25

Describe the erythrocytic stages of malaria

Back 25

-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

Front 26

Describe the Pathogenesis of malaria

Back 26

-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

Front 27

What causes cerebral malaria? Describe cerebral malaria

Back 27

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.

Front 28

What are the long term effects of repeated malaria infection?

Back 28

-Learning deficit
-Reduced growth rate
-Spontaneous abortion
-All may be due to prolonged metabolic acidosis

Front 29

What are the clinical signs and symptoms of malaria?

Back 29

-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

Front 30

What pathogenesis is limited to P. falciparum?

Back 30

-Cerebral malaria
-Retinopathy

Front 31

What is unique to the P.vivax life cycle?

Back 31

-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

Front 32

When does most death from malaria occur?

Back 32

Between 8 months and 5 years of age

Front 33

Back 33

EM of RBC infected with P. falciparum. Surface has little histadine rich nobs that it uses to attach to the surface of endothelial cells

Front 34

Back 34

This is a monkey with cerebral malaria from P. falciparum. The parasite is inside the vessel in the precapillary area.

Front 35

How do you diagnose malaria?

Back 35

-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.

Front 36

What does the treatment depend on?

Back 36

-Type of malaria
-Knowledge of regional resistance
-Severity of illness (oral vs IV)
-Age of patient

Front 37

Where is drug resistance malaria located?

Back 37

Africa, S. Amoeria, China and South Asia, SE Asia

Front 38

Why is P. falciparum the strain with the most resistance?

Back 38

It grows faster thus develops resistance faster

Front 39

What is the parent compound for most antimalarial drugs?

Back 39

Quinine
Esp. good against P. falciparum

Front 40

Describe chloriquine

Back 40

It is an older quinine derivative to which there is must resistance

Front 41

Describe mefloquine

Back 41

It is a newer quinine derivative used for resistance strains of P. falciparum

Front 42

What are the current drugs of choice for malaria?

Back 42

Atovoquan
Proguanil

Front 43

Describe antifolate treatment

Back 43

Sulfonamides/Dapsone inhibits Dihydropteroate Synthetase

Pyrimethamine/Proguanil inhibits Dihydrofolate reductase

Front 44

Describe antimalarial prophylaxis

Back 44

-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