Seminar 1: Apicomplexes: Plasmodium

Question 1

Malaria is a __-borne disease caused by 5 protozoa of the ____ genus

Answer 1

mosquito

plasmodium

Question 2

What are the 3 primary cycles of plasmodium?

Answer 2

1. exo-erythrocycle: human liver stage
2. Erythrocytic cycle: human blood stage
3. sporogonic cycle: mosquito stages

Question 3

During which of the 3 stages does the patient appear sick (clinical manifestation)?

Answer 3

Erythrocytic cycle (human blood stage)

Question 4

Explain the 1st stage of plasmodium (exo-erythrocytic cycle)

Answer 4

a. mosquito takes a blood meal from human and injects sporozoites (saliva transmitted)
b. sporozoites enter and infect the human liver cells
c. schizonts in liver cells asexually reproduces; forms merozoites. The schizont ruptures and releases these merozoites
d. merozoites enter bloodstream (stage 2)

Question 5

Explain the 2nd stage of plasmodium (erythrocytic stage)

Answer 5

a. merozoites enter blood stream from ruptured liver cell
b. immature trophozoite (ring stage) in blood cells undergo 1: sexual rep or 2: asexual rep to become a mature trophozoite
1: asexual rep –> schizont –> schizont ruptures and cycle repeats
2. sexual rep: gametocytes form and mosquito ingests them when it takes a blood meal –> begins 3rd cycle

Question 7

Explain the 3rd cycle of plasmodium (sporogonic cycle)

Answer 7

a. mosquito takes a blood meal: ingests gametocytes from the bloodstream
b. microgamete enters the macrogamete and becomes an ookinete
c. ookinete forms into an oocyst, which grows and ruptures
d. ruptured oocyst releases sporozoites, which goes to saliva gland
e. mosquito takes a blood meal, injecting sporozoites (stage 1 of cycle begins again)

Question 8

Give a simplified version of the life cycle of plasmodium in the mosquito

Answer 8

gametes –> zygotes –> ookinetes –> oocysts (ruptures in 2 weeks) –> sporozoites go to saliva

Question 9

Do mosquitos become “immune” to plasmodium? Explain

Answer 9

• insects have a simple innate immune system: no memory cells
• “Immune Priming” may occur: repeated exposures= better immune response
  –> “remembers” interaction b/w bacteria and parasite-invaded midgut cells (so it’s not reacting to the parasite itself)
• midgut cells invaded produce high levels of nitric oxide species

Question 10

What’s the main symptom of Malaria?

Answer 10

Fever paroxysm

Question 11

Explain what you might experience if you were infected with plasmodium

Answer 11

FEVER
= inflammation (immune cells recognize damage/ pathogens & release pyrogenic cytokines, which induce fever

You’d experience:
- episodes of high fever, starting with periodic chills –> sweating –> fever decline
- 15-60min of cold/ shivering
- 2-6hr of fever
- 2-4hr of profuse sweating after fever rapidly drops

Question 12

The chills, shivers, and rigors associated with malaria are caused by ____

=

Answer 12

hemozoin

= a waste product from the parasite’s digestion of blood. It’s toxic, so causes fever