Blood and Tissue Parasites 1: Malaria

Question 1

Of the 4 Plasmodium strains, which one is most lethal and which is most common (both in the world and in the U.S.)?

Answer 1

P. falciparum is most lethal; P. vivax is the most common both worldwide and in the U.S.

Question 2

Where in the U.S. are Anopheles mosquitos capable of transmitting malaria found?

Answer 2

In all 48 contiguous states

Question 3

What genetic trait confers complete resistance to P. vivax malaria, and in which area of the world is this trait most common?

Answer 3

The absence of Duffy antigen in RBCs; West Africa

Question 4

List 3 genetic traits that provide some protection against all malaria infections.

Answer 4

Sickle cell (Hb S) trait, Hb C trait, and Thalassemias (other less important traits include G6PD deficiency, glycophorin C deficiency/Leach phenotype, and hereditary elliptocytosis)

Question 5

What genetic trait is most strongly implicated in the development of P. vivax resistance and P. falciparum increase in West Africa, and what is the main effect of carrying this trait?

Answer 5

Duffy antigen (-); vivax merozoites can’t find and invade erythrocytes if the Duffy antigen is missing

Question 6

The malaria paroxysm is a characteristic pattern of illness that appears after a period of constitutional symptoms in the infected host. What are the 3 stages of this paroxysm and how long does each stage typically last?

Answer 6

Cold stage: 15-60 min
Hot stage: 2-6 hours
Sweating stage: 2-4 hours

Question 7

Correlate the changes in a patient’s body temperature with what the patient subjectively experiences throughout the 3 stages of the malaria paroxysm.

Answer 7

Cold stage - patient has fever but feels cold, vigorous shivering
Hot stage - temperature stays steady, patient feels intense heat and throbbing headache
Sweating stage - temperature declines, profuse sweating, patient feels exhausted and sleeps

Question 8

In which Plasmodium species does the patient’s body temperature drop instead of rise during the malaria paroxysm?

Answer 8

P. falciparum

Question 9

During what stage of the malaria paroxysm are Plasmodium protozoa released from lysed RBCs?

Answer 9

Cold stage

Question 10

Where in the body are the Plasmodium parasites during the hot stage of the malaria paroxysm?

Answer 10

In the bloodstream/circulation

Question 11

What Plasmodium behavior causes the return to normal body temperature during the sweating stage of the malaria paroxysm?

Answer 11

The merozoites re-enter new RBCs

Question 12

What term describes the situation in which parasitemia temporarily falls below detectable levels? Where in the human body do Plasmodium sporozoites go during this time?

Answer 12

Recrudescence; sporozoites are in the liver / hepatocytes

Question 13

Which Plasmodium species has the shortest incubation period before malaria symptoms begin to appear?

Answer 13

P. falciparum

Question 14

Give 5 potentially lethal manifestations of P. falciparum infection.

Answer 14

Severe anemia, cerebral infection, respiratory failure, renal failure, and severe malaria of preganancy

Question 15

One feature of P. falciparum that makes it particularly nasty is its ability to sequester where in the body? Where else does this P. falciparum hang out, that makes the parasitemia appear falsely low?

Answer 15

In the deep venous vasculature; also adheres to capillary walls (so observed parasitemia of >5% is considered life-threatening)

Question 16

Besides anemia, give 3 effects of P. falciparum in the body.

Answer 16

Pulmonary edema, hypoglycemia, and metabolic acidosis

Question 17

What P. falciparum protein displays 2-18% changes in expression per cell per generation, leading to enormous antigenic variation throughout the course of an infection? To what receptor does this protein bind?

Answer 17

PfEMP-1 (Plasmodium falciparum Erythrocyte Membrane Protein 1); CD36 endothelial receptor

Question 18

What complication of P. falciparum involves ring hemorrhages, perivascular leukocyte infiltrates, endothelial cell activation, inflammatory cytokines and mediators, and functional obstruction that leads to reduced local delivery of oxygen and glucose?

Answer 18

Fatal cerebral malaria

Question 19

What complication of P. falciparum occurs when mature parasites interact with syncytiotrophoblastic chondroitin sulfate A (CSA), hyaluronic acid, and immunoglobulins?

Answer 19

Malaria of pregnancy / placental malaria

Question 20

Give 2 reasons why P. vivax and P. ovale are less deadly than P. falciparum.

Answer 20

They prefer to infect only reticulocytes and do not exhibit sequestration

Question 21

Which Plasmodium species prefers to infect older RBCs, has a 72-hour paroxysmal cycle, and has an incubation period of 40 days (the longest of all the species)?

Answer 21

P. malariae

Question 22

P. malariae patients can remain asymptomatic for many years, after which they typically present with what syndrome?

Answer 22

Nephrotic syndrome (proteinuria)

Question 23

What level of P. falciparum parasitemia is considered life threatening? What level is considered fatal unless exchange transfusion occurs?

Answer 23

5%, 15%

Question 24

How long does it take to check for chloroquine resistance in a Plasmodium?

Answer 24

Effects should start at 6 hours and be complete by 24 hours