Blood Born Parasites - Part 1

Question 1

What are the four major species that cause malaria? Which is the most lethal? Which is most common? Vector?

Answer 1

Plasmodium falciparum, vivax, ovale, malaria; Falciparum; Vivax; Anopheles mosquito

Question 2

Distributions of Plasmodium species

Answer 2

Vivax: All malarious areas except sub-Saharan Africa; Malariae: All malarious areas (spotty); Ovale: Western Africa; Falciparum: sub-Saharan Africa, Southeast Asia, South America

Question 3

Conditions that confer resistance

Answer 3

Duff antigen absence on RBCs: vivax; Hereditary elliptocytosis, glycophorin C deficiency, Sickle Cell Trait, Thalassaemias, G6PD deficiency

Question 4

How does Thalassemia prevent malaria infection?

Answer 4

RBC life is shorter and therefore less hospitable to ALL plasmodium species

Question 5

What is the definitive host for plasmodium species? Intermediate host? What is the general cycle of malaria? What cycles do merozoites undergo w/i RBCs?

Answer 5

Mosquito; Humans; Mosquito-> Humans-> Blood-> Liver-> Blood-> Mosquito; Sexual and Asexual

Question 6

Malarial Syx

Answer 6

Anemia, Headache, Fever, Fatigue, Chills, Sweating, Dry cough, Splenomegaly, N/V

Question 7

What is the “Malaria Paroxysm”? Trend for falciparum? Trend for vivax/ovale?

Answer 7

4-8 hr period beginning with sudden onset of chills, followed by intense heat, severe headache, fatigue, dizziness, anorexia, myalgia, nausea. Patient then falls asleep and feels better; Mostly elevated fever with transient break at third day; Fever spikes at 1st and 3rd day.

Question 8

What is Malarial Recrudescence?

Answer 8

The situation in which parasitemia falls below detectable levels and then resurges.

Question 9

What is an important feature of the pathogenesis of P. falciparum?

Answer 9

Can sequester in the deep venous microvasculature

Question 10

What percentage of P. falciparum parasitemia is considered life-threatening?

Answer 10

> 2-3%

Question 11

What are the major Syx associated with P. falciparum infection?

Answer 11

Hypoglycemia, Anemia, Pulmonary Edema/Respiratory Distress, Metabolic (Lactic) Acidosis

Question 12

What is PfEMP-1 and how does it contribute to malaria pathogenesis?

Answer 12

P. falciparum erythrocyte membrane protein-1 (PfEMP-1) is expressed on infected erythrocytes and binds to CD36 receptors on endothelium results in RBC sequestration

Question 13

What is the classic histopathological finding of fatal cerebral malaria?

Answer 13

Intense sequestration of parasites in cerebral microvasculature accompanied by ring hemorrhages, perivascular leukocyte infiltrates, and immunohistochem evidence for endothelial activation

Question 14

What are the effects of malarial infection of pregnancy? What is associated with sequestration of mature parasites in the placenta?

Answer 14

Maternal morbidity/mortality, inrauterine growth retardation, premature delivery, low birth weight, increased newborn mortality; Syncytiotrophoblastic chondroitin sulfate A (CSA)

Question 15

What are typical histological findings of P. falciparum trophozoite? gametocyte? What stain is primarily used?

Answer 15

Giemsa stain reveals ring-form plasmodium falciparum trophozoite, banana-shaped gametocyte

Question 16

What attributes to low mortality rates associated with P. vivax and P. ovale?

Answer 16

Favor reticulocytes (and therefore low parasitemia levels) and no RBC sequestration

Question 17

Histological findings of vivax?

Answer 17

Large chromatin dots, amoeboid cytoplasm, RBCs enlarged to 1.5 times and distorted, optimal conditions: Schueffner dots

Question 18

Histological findings of ovale?

Answer 18

Schueffner dots early on (bigger and heavier than those seen in vivax) CHARACTERISTIC: spiked edges

Question 19

What is the periodicity of malariae paroxysms? How long can chronic P. malariae last? What are complications of P. malariae in young?

Answer 19

3 days; Can be infected and asymptomatic for many years; Nephrotic syndrome

Question 20

What types of RBCs does P. malariae infect? How long is the incubation period? What are typical patient presentations?

Answer 20

Older RBCs; Incubation is 40 days (longest)

Question 21

What are histological findings of P. malariae?

Answer 21

Large signet ring, RBCs small-normal size, merozoites form daisy head arrangement

Question 22

What pathogen accounts for 70% of malaria cases in South East Asia? What makes this particular pathogen so virulent?

Answer 22

P. knowlesi; Replicates and completes blood stage cycle in 24 hrs -> high loads of parasitemia

Question 23

How to differentiate between P. knowlesi and malariae? Why?

Answer 23

Use molecular detection assays because knowlesi and malariae appear very similar

Question 24

Important factors for making a Dx of malaria

Answer 24

Travel: Where, when, how long; Blood Films: thick and thin smears, stains, draw before fever to catch infected cells

Question 25

What is the percentage of parasitemia in most cases worldwide? How long should it take for a chloroquine sensitive strain of malaria to react to chloroquine?

Answer 25

<3%; Smear should be reduced at 6 hours, negative at 24hrs

Question 26

What are the main antimalarial drugs and important points

Answer 26

Chloroquine (attacks RBC stage), paraquinine (eliminates liver stage for ovale and vivax, used if gametocytes seen with P. falciparum).