Plasmodium spp

Question 1

Describe a diagnostic method to differentiate between different plasmodium infections.

Answer 1

Look for key morphological features in blood smears of infected RBCs, particularly of trophozoites and gametocytes within these.

Question 2

Define suppressive cure for anti-malarial therapy.

Answer 2

When therapy can be targeted to the bloodstream forms alone. This is particularly useful for P. falciparum and P. malariae which have no liver stage.

Question 3

Define radical cure for anti-malarial therapy.

Answer 3

Used to remove bloodstream infection AND eradicate slow-replicating hypnozoites form the liver to prevent relapse.

Question 4

What is the significance of “dormant hypnozoites” amongst Plasmodium species?

Answer 4

Dormant hypnozoites are forms that persist in the liver long after erythrocytic forms disappear. These can present in P. vivax and P. ovale infections.

Question 5

Pertaining to the Plasmodium life cycle, ______ are infectious for humans, ______ are infectious for erythrocytes, and _______ are infectious for mosquitoes.

Answer 5

Sporozoites for humans;
merozoites for RBCs;
Gametocytes for mosquitoes

Question 6

List at least 3 diseases in which a heterozygote’s RBCs are less hospitable for plasmodia.

Answer 6

1. Glucose-6-phosphate dehydrogenase deficiency
2. Thalassemia (deficiency of alpha/beta Hb chains)
3. Sickle-cell anemia

Question 7

What are the 3 modes in which Plasmodia can be transmitted to humans?

Answer 7

1. Bite of female Anopheles mosquitos
2. Blood transfusion
3. maternal-fetal route (rare)

Question 8

What Plasmodium species present with “tertian” fevers? What of “quartan” fevers?

Answer 8

P. vivax, P. ovale and P. falciparum work on a 48-hour tertian fever cycles. P malariae has a 72-hour quartan fever.

Question 9

Briefly describe the Erythrocytic cycle.

Answer 9

1. Merozoite infects RBC to become a vacuolated ring form.
2. Ring form enlarges into Trophozoite
3. Schizont forms from nuclear division
4. Schozont is cleaves to produce many new merozoites from lysed RBC

Question 10

Distinguish the trophozoite morphological features between the 4 Plasmodium species

Answer 10

1. P. vivax = pleomorphic
2. P. ovale = fimbriated, oval RBC
3. P. malariae = narrow band-forms
4. P. falciparum = schizonts or trophs become adhesive

Question 11

What treatments are first-line agents against P. falciparum?

Answer 11

Atovaquone and Artemisinins