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Microbiology > Parasitology Exam 3: Malaria and Babesia > Flashcards

Parasitology Exam 3: Malaria and Babesia Flashcards

1
Q

What genus of organisms cause malaria?

A

Plasmodium sp.

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2
Q

What is the major species associated with the most deadly malarial infections worldwide?

A

Plasmodium falciparum

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3
Q

What are the most common malarial infections (95% of infections) ?

A

P. vivax and P. falciparum

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4
Q

When Plasmodium bites a human, what stage do they infect the human with? (i.e. what is the infective stage of Plasmodium in humans)

A

Sporozoites

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5
Q

After the injection of sporozoites in the human, what happens next in the malarial life cycle? (this happens in humans)

A

Sporozoites enter the blood and are carried to the liver where they grow in hepatocytes. This initiates the preerythrocytic or primary exoerythrocytic cycle.

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6
Q

What is schizogony?

A

Rapid division and multiplication of sporozoites

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7
Q

Intracellular sporozoites mature into _______. (this happens in humans)

A

Schizonts

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8
Q

After the schizont ruptures, what do they release? Where do these go? What cycle does this initiate? (this happens in humans)

A

Release merozoites; leave the liver to invade RBCs; this initiates the erythrocytic cycle

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9
Q

Merozoites feed on hemoglobin to become mature ___________. (this happens in humans)

A

Trophozoites

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10
Q

Tropozoites multiply and mature into _______. (this happens in humans)

A

Schizonts

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11
Q

Mature schizonts contain ________ which are released into the bloodstream and start a new cycle of ___________. (this happens in humans)

A

Merozoites; erythrocytic schizogony

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12
Q

Merozoites can begin to undergo development into male and female __________. These are then ingested by the mosquito when it takes a blood meal. (this happens in humans)

A

Gametocytes

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13
Q

Describe the malarial life cycle that occurs in MOSQUITOES.

A
  1. Mosquito takes a blood meal –> ingests gametocytes
  2. Male + female gametocytes generate zygotes
  3. Zygotes become motile and form ookinetes
  4. Ookinetes develop into oocyts
  5. Oocyts mature and release sporozoites
  6. Sporozoites are introduced into a new human host and cycle continues
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14
Q

Describe the malarial life cycle that occurs in HUMANS.

A
  1. Anopheles takes blood meal and releases sporozoites
  2. Sporozoites carried to the liver, enter hepatocytes –> initiation of preeythrocytic/primary exoerythrocytic cycle, schizogony occurs
  3. Sporozoites mature into schizonts
  4. Schizont ruptures and releases merozoites
  5. Merozoites leave the liver and invade RBC –> erythrocytic cycle
  6. Merozoites feed on Hgb and become mature trophozoites
  7. Trophozoites multiply and mature into schizonts
  8. Schizonts again rupture and release more merozoites initiating a new cycle of erythrocytic schizogony
  9. Some merozoites undergo development into gametocytes
  10. Gametocytes ingested by new mosquito
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15
Q

What are the possible diagnostic stages of malaria in humans?

A

Detection of immature trophozoites AKA merozoites (ring stage), mature trophozoites, schizonts, or gametocytes in the thick or thin blood smear.

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16
Q

Where do sporozoites invade? What cycle does this initiate?
Where do merozoites invade? What cycle does this initiate?

A

Sporozoites invade hepatocytes (liver) –> preerythrocytic cycle
Merozoites invade RBC –> erythrocytic cycle

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17
Q

What stage of malarial infection is the ring form we can see in blood smears?

A

Merozoites (immature trophozoites)

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18
Q

What is dormant schizogony and what organisms can exhibit this?

A

Organisms remaining quiescent in the liver –> hypnozoites
Can lead to relapse
P. vivax and P. ovale

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19
Q

What are hypnozoites and what organisms can display this?

A

Resting stage of malarial infection remaining quiescent in the liver
P. vivax and P. ovale

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20
Q

Microgametocytes vs Macrogametocytes

A

Microgametocytes = male sexual stage of malaria
Macrogametocytes = female sexual stage of malaria

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21
Q

Schizont

A

A multinucleated cell undergoing schizogony, contains merozoites

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22
Q

Exo-erythrocytic cycle vs erythrocytic cycle

A

Exoerythrocytic cycle = occurs in liver cells
Erythrocytic cycle = occurs in RBCs

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23
Q

Definitive vs intermediate host of malaria

A

Definitive = Anopheles mosquito (sexual stages found)
Intermediate = humans (asexual stages found)

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24
Q

What is the sexual stage of malaria?

A

Gametocytes

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25
What are the 2 basic sign/symptoms of malarial infection? What stage causes these symptoms?
Fevers and rigor, all clinical symptoms caused by the asexual erythrocytic or blood stage parasites
26
What 3 stages does a classical malarial attack consist of?
1. A cold stage 2. A hot stage 3. A sweating stage
27
Tertian parasites vs quartan parasites
Tertian = Symptoms/attacks occur every 2 days Quartan = Symptoms/attacks occur every 3 days
28
What is cerebral malaria and what Plasmodium species is associated with this?
Severe form of malaria where P. falciparum-infected RBCs adhere to the endothelium of blood vessels in the brain; associated with high mortality
29
Hyperparasitemia
>5% of RBCs are parasitized
30
Describe STANDOUT features of P. vivax that help us identify it
- ONLY infects **reticulocytes** - Dormant schizogony CAN occur --> **hypnozoites, recrudescence** - Contain **Schuffner dots** - Mature schizont contains **12-24 merozoites** - Tertian
31
Describe STANDOUT features of P. ovale that help us identify it
- ONLY infects **reticulocytes** - Distinctive **oval-shaped cells with ragged edges** - Contain **Schuffner dots** - Dormant schizogony CAN occur --> **hypnozoites, relapses** - Mature schizont contains **~8 merozoites** - Tertian
32
How to differentiate P. ovale from P. vivax?
The main difference between them is P. ovale has oval-shaped cells with ragged edges and schizont contains less merozoites (~8). P. vivax schizont can contain 12-24 merozoites. They both only infect reticulocytes, can cause hypnozoites, are Tertian, and contain Schuffner dots.
33
Describe STANDOUT features of P. malariae that help us identify it
- Infects **OLD RBCs** - Quartan (infects every 72 hours) - May enter a period of **recrudescence** - Developing rings may exhibit **band forms** - Mature schizont contains **6-12 merozoites** - Can cause **kidney problems**
34
What is recrudescence?
Recurrence of symptoms; repeated malarial attack due to survival of parasites in RBCs
35
Relapse vs recrudescence
Relapse = recurrence of disease after it has been cured Recrudescence = repeated malarial attack due to survival of parasites
36
Describe STANDOUT features of P. falciparum that help us identify it
- Infects **All ages of RBCs** - Schizogony occurs in **liver, BM, and spleen** rather than circulating blood - Exhibit **cytoadherence** - Tertian - **Multiple parasite infections per cell** - Rings have **2 dots of chromatin** - **Maurer dots** - Gametocytes are **crescent/banana shaped** - Can be associated with **Blackwater fever, cerebral malaria, and DIC**
37
Which Plasmodium sp exhibit Schuffner dots?
P. vivax, P. ovale
38
Which Plasmodium sp. only infect old RBCs?
P. malariae
39
Which Plasmodium sp. can infect any age RBCs?
P. falciparum, P. knowlesi
40
Which Plasmodium sp. can only infect reticuloctes?
P. vivax, P. ovale
41
What are Maurer dots and which Plasmodium sp. are they associated with?
Coarse granulation in the RBC cytoplasm, blue in color Associated with P. falciparum
42
What are applique or accole ring forms? What Plasmodium sp. are they associated with?
Delicate ring forms with 2 dots of chromatin located on the surface of the RBC Associated with P. falciparum
43
Cytoadherence
Parasite binds to the surface of RBCs and to vascular endothelial cells, associated with severe malaria (P. falciparum)
44
What is Blackwater fever?
Result of RBC lysis, release of HGB into bloodstream and urine causing discoloration Associated with P. falciparum
45
What is the major cause of death in P. falciparum infections?
Cerebral malaria
46
Name 2 features of P. falciparum that allow infection to become very serious.
DIC, Cerebral malaria, Blackwater fever
47
Describe STANDOUT features of P. knowlesi that help us identify it
- Invades **all ages of RBCs** - AKA **The Fifth Human Malaria/Simian Malaria** - Associated with **Southeast Asia** - Early blood stages resemble P. falciparum infections - Late blood stages resemble P. malariae infections
48
What test is used to diagnose Malaria and Babesia parasites?
Thick and thin blood smear, 200-300 oil immersion fields examined
49
Why is it important to speciate Malarial infections?
P. falciparum and P. knowlesi can be fatal and need treated ASAP The other species are not as serious
50
What is Acridine orange stain used for?
Quantitative buffy coat method
51
How do we report the presence/absence of malarial/babesia parasites?
Absence = NPF Presence = speciate and quantify % parasitemia
52
How is % parasitemia reported?
% of cells counted that contain parasites Extracellular forms NOT counted, Gametocytes NOT included b/c they are not the infectious form
53
What is the current suggested therapy for P. falciparum infections?
ACT: Artemisinin combination therapy
54
What is the vector of Babesia spp.?
Ixodes (deer tick)
55
What Babesia spp. is the most common cause of infection in the US?
B. microti
56
How is the Babesia life cycle different from the malarial life cycle?
- No exoerythrocytic stage --> Sporozoites invade RBCs directly - Trophozoites reproduce by binary fission instead of schizogony
57
What is the definitive, intermediate, and Incidental/dead-end host of Babesia?
Definitive = Ixodes tick Intermediate = Rodents (white-footed mouse) Incidental = humans
58
Describe the life cycle of Babesia spp.
1. Infected tick introduces sporozoites into mouse host 2. Sporozoites enter RBCs and undergo asexual reproduction 3. Some parasites differentiate into male/female gametes in the blood 4. Gametes ingested by another tick, undergo sporogenic cycle resulting in sporozoites 5. Tick introduces sporozoites into human 6. Sporozoites enter human RBCs and undergo asexual reproduction Humans = dead end host, cannot spread any further
59
Babesia microscopic morphology (Standout features)
- Ring forms OUTSIDE of red cells - 2-3 rings INSIDE red cells - **Maltese cross forms**, diagnostic for Babesia infection
60
What are the infective and diagnostic stages of Babesia sp.?
Infective: Sporozoites introduced into mouse or human Diagnostic: Trophozoite or merozoite

Microbiology (24 decks)

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