Micro- Malaria

Question 1

What is algid malaria?

Answer 1

Complication of falciparum malaria where there is:

1. vascular collapse
2. shock
3. drop in body temperature

Question 2

What is bilious remittent fever?

Answer 2

Impairment of liver function an marked jaundice associated with falciparum malaria

Question 3

What is “blackwater” fever?

Answer 3

Complication of falciparum malaria where there is massive hemolysis and hemoglobinuria.

Question 4

What is cerebral malaria?

Answer 4

Complication of falciparum malaria where there is:

1. cerebral capillary obstruction
2. brain congestion
3. brain swelling

Question 5

What form of the malaria parasite is responsible for infecting more mosquitoes?

Answer 5

Gametocyte [male or female] in the RBC

*females are called macrogametocytes, males are called microgametocytes

Question 6

What 2 strains of malaria have hypnozoites?

Answer 6

Hypnozoite is a dormant form of malaria in liver cells

1. Plasmodium vivax
2. plasmodium ovale

Question 7

What is a merozoite?

Answer 7

form of the malaria parasite that results from asexual multiplication within the RBC
It is released from the mature schizont to infect other RBCs

Question 8

What is the ring stage?

Answer 8

First stage of development of malaria parasites in the RBC.

It consists of a ring of cytoplasm and a dot of nuclear material surrounding a vacuole

Question 9

What area is considered to be a zone of chloroquine-resistant P. falciparum?

Answer 9

at the present time, nearly ALL P. falciparum are chloroquine resistant except in:

1. Haiti
2. Central America north of the Panama Canal

Question 10

What are the 5 species that can cause malaria in humans?

Answer 10

P. falciparum
P. vivax
P. ovale
P. knowlesi [S.E. Asia--Malaysia] 
P. malariae

Question 11

P. knowlesi was prior thought to only be a primate pathogen but now it has been shown to infect humans in what area?
What does P. knowlesi resemble microscopically? How does it different from this strain clinically?

Answer 11

It infects humans in Southeast Asia, specifically Malaysia

Microscopically it resembles P. malariae but it has a MUCH more severe disease

Question 12

Describe the pathogenesis of malaria protozoa parasites.

What vector transits the plasmodium to humans?

Answer 12

1. Plasmodium sporozoites are transmitted to humans via Anopheles mosquitos that take a blood meal
2. In liver cells, sporozoites mature into schizonts and mature into merozoites.
3. Merozoites released from the liver invade RBCs and attach themselves to specific binding sites on RBC
4. in RBC, merozoites feed on Hb and other proteins and mature into trophozoites
5. Trophozoites undergo nuclear division [without cell division] to form 16-32 parasite nuclei [Schizonts] in a single RBC
6. RBC ruptures, and schizonts release merozoites to infect new RBCs

Question 13

What are the 4 developmental stages of malaria apparent in peripheral blood?

Answer 13

1. ring stage - early, asexual stage in RBC, ring-shaped
2. Trophozoites- further development asexual stage that is larger, less ring-shaped, with accumulation of malarial pigment [hemozoin]
3. Schizonts- late asexual stage where the parasite has divided into merozoites each containing chromatin.
4. Gametocytes- sexual stage. The forms have no relevance to disease, but are necessary for infection of mosquitos

Question 14

Describe the appearance of P. vivax in trophozoite stage blood smears.

1. RBC appearance
2. trophozoite appearance

Answer 14

1. Erythrocyte it lives in is usually younger and thus LARGER than other RBCs
2. amoeboid appearance
3. Schuffner’s dots = inclusion of RBC [little pink dots]

Question 15

Describe the appearance of P. ovale in trophozoite stage blood smears.

Answer 15

1. oval, tear drop or elongated RBC with “pulled out” fimbriated cell membranes
2. James dots= inclusion bodies

Question 16

What can the number of merozoites in the schizonts clue you in to?

Answer 16

identification of the plasmodial species

Question 17

Which peripheral blood stage is NOT important for disease pathogenesis, but is crucial for infection of mosquitoes?

Answer 17

gametocytes

Question 18

For what 2 species of plasmodium is it important to treat for the peripheral blood stages AND with primaquine to eradicate hypnozoites from the liver?

Answer 18

ovale and vivax

Question 19

Describe thick blood film for malarial detection.

Answer 19

1. Lyse RBCs with distilled water or saponin to leave WBC, parasite, platelets
   - more sensitive than thin film because it has larger volume of sample
2. stain with Giemsa or pH 7.2-7.4 stain
   - usually hematologic stains are lower pH but if you use these for malarial suspicion, you may not see Schuffners dots

Question 20

What are the 3 main things the thin blood film allows you to do?

Answer 20

1. morphological differentiation between plasmodium species
2. differentiate plasmodium from babesia
3. estimate the percentage of parasitemia

Question 21

What plasmodium species is associated with:

1. Schuffner’s dots
2. James dots
3. Maurer’s lefts

Answer 21

1. P. vivax
2. P. ovale
3. P. falciparum

Question 22

In addition to thick and thin blood films, what techniques are used to diagnose malaria?

Answer 22

1. EIA [used mostly outside the US]
   - P. falciparum vs the other species
   - Some can do P vivax
2. PCR
   - used in reference laboratories
   - useful for identifying dual species infections
3. Ab tests
   - reference labs
   - NOT useful for individual cases

Question 23

How many cases of malaria are there worldwide per year?
What age group/area has the highest mortality?
How much of the world’s population lives in an endemic zone?

Answer 23

300-500 million cases/year
Highest mortality in children under 5 in Sub-Saharan Africa
1/2 the word’s population lives in an endemic zone

Question 24

In parts of Africa and Southeast Asia, what drugs are P. falciparum resistant to?

Answer 24

1. chloroquine
2. sulfadoxine/proguanil
3. proguanil
4. mefloquine

Question 25

What is the only location [except for RARE exceptions] where P. ovale occurs?

Answer 25

Central and Western Sub-Saharan Africa

Question 26

What is the specific binding site on P. falciparum and P. vivax that merozoites bind to ?

Answer 26

P. falciparum = glycophorin antigen | P. vivax = Duffy blood group antigen

Question 27

What determines the clinical picture of malaria?

Answer 27

1. age and immune status of the patient 2. species of parasite - falciparum is most virulent

Question 28

One brood of parasites becomes dominant and is responsible for the synchronous nature of the clinical symptoms of malaria [cyclic paroxysms]. How do they elicit symptoms?

Answer 28

1. replicate inside RBC and then induce cytolysis 2. release toxic metabolic byproducts into the bloodstream 3. since many RBCs rupture at the same time, the host experience : - flu like symptoms - anemia

Question 29

What are the 3 things plasmodium species do to cause anemia?

Answer 29

1. RBC lysis 2. suppression of hematopoiesis 3. increased clearance of RBC by the spleen [over time they also cause thrombocytopenia and hepatosplenomegaly]

Question 30

Why is the level of parasitemia higher for P. falciparum then the other plasmodium species? What clinical effects does this lead to?

Answer 30

It infects ALL RBCs [young, middle age, old] This means it makes more merozoites, destroying even more RBCs leading to: lack of O2 to tissues

Question 31

Why does P. falciparum cause hypoglycemia and lactic acidosis?

Answer 31

P. falciparum uses glucose as their energy source and because they metabolize it 70x faster than the RBCs they live in, this causes hypoglycemia/lactic acidosis

Question 32

What 3 factors are considered when deciding treatment options for plasmodium?

Answer 32

1. infecting species 2. geographical area where infection was acquired 3. severity of the disease

Question 33

What are the 3 "r" problems with management of malaria?

Answer 33

1. recrudescence- controllable number of parasites remain latent in RBCs in the blood stream due to inadequate immune response or antimalarial therapy and reactivate with trauma or immunosuppression 2. relapse- hypnozoites [vivax/ovale] in the liver reactivate 3. resistance- anti malarial drugs become ineffective

Question 34

What is the drug of choice for non-resistant strains of Plasmodium? Which plasmodium species does it kill? What 2 situations do you need supplement/ a different drug?

Answer 34

Chloroquine is drug of choice for all 5 species if they are non-resistant. 1. It does NOT kill hypnozoites so you need to use PRIMAQUINE to prevent drug relapse 2. it does NOT kill resistant strains so you need MEFLOQUINE, malarone [atovaquone/proguanil] or quinine

Question 35

In EXTREME cases of falciparum malaria, what technique can be used?

Answer 35

Exchange transfusion to decrease the level of parasitemia

Question 36

What are the 2 reasons morbidity and mortality are greater for P. falciparum?

Answer 36

1. increased parasitemia -- lack of O2 to tissues, lactic acidosis, hypoglycemia 2. cytoadherence- infected RBCs have proteinaceous knobs on the surface of the RBC that stick to endothelial cell lining in microvasculature of the CNS, kidney and lungs. This leads to aggregation [rosetting] of uninfected RBCs sequestering them and resulting in cerebral malaria/kidney failure

Question 37

What is prevention of malaria?

Answer 37

1. DEET insect repellent 2. premethrin-treated clothes and bed nets 3. staying indoors at night/early morning 4. if travelling to endemic areas - chloroquine if not resistant - if resistant area : mefloquine, malarone, proguanil, primaquine, doxy