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BSC Zoology - Parasitology > 17. Protozoa (Plasmodium) > Flashcards

17. Protozoa (Plasmodium) Flashcards

1
Q

what is one of the oldest diseases known to man?

A

Malaria

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2
Q

where does the name “malaria” come from?

A

the italian words mal’aria meaning bad air

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3
Q

was malaria in canada? where?

A

yes, in upper and lower canada and out into the prairies

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4
Q

where does malaria rank in “causes of death” for infectious pathogens?

A

third after HIV/AIDS and tuberculosis

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5
Q

how is malaria transmitted?

A

from person to person via the bite of a females Anopheles mosquito

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6
Q

in Plasmodium an intracellular or extracellular parasite?

A

obligate intracellular

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7
Q

what time of day does the female mosquito bite?

A

dusk and dawn

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8
Q

are all Anopheles species able to transmit the parasite?

A

no, only about 60 in 380

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9
Q

the accumulation of what spreads the disease?

A

water

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10
Q

what are the four parasite species that cause malaria in humans?

A

Plasmodium falciparum
Plasmodium vivax
Plasmodium malariae
Plasmodium ovale

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11
Q

which are the most common parasite species to cause malaria in humans?`

A

p. falciparum and p. vivax

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12
Q

what are the major features of P. falciparum?

A
  • the most important species, responsible for ~50 of all malaria cases worldwide and nearly all morbidity and mortality from severe malaria
  • found in the propics and sub-tropics
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13
Q

what are the major features of P. vivax?

A
  • widest geographical distribution
  • seen in tropical and sub-tropical areas, but rare in Africa
  • estimated to cause 43% of all malaria cases in the world
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14
Q

what are the major features of P. ovale?

A
  • relatively rarely encountered

- primarily seen in tropical Africa, especially in the west coast, but has been reported in South America and Asia

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15
Q

what are the major features of P. malariae?

A
  • responsible for only 7% of malaria cases

- occurs mainly in sub-tropical climates

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16
Q

what other vertebrates are also infected by Plasmodium parasites?

A
  • non-human primates
  • rodents
  • birds
  • lizards
  • ungulates
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17
Q

who is the DH of Plasmodium?

A

Anopheles mosquito

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18
Q

who is the IH of Plasmodium?

A

human

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19
Q

what is special about P. vivax and P. ovale?

A

they have a dormant liver stage: hypnozoite

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20
Q

what Plasmodium stage does the Anopheles mosquito inoculate the human with?

A

sporozoites

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21
Q

what happens to the sporozoites in the human, in the liver?

A

they mature into schizonts

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22
Q

what happens to the schizonts?

A

they rupture and release merozoites

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23
Q

what does the hypnozoite do?

A

it can persist in the liver and cause relapses by invading the bloodstream weeks or even years later

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24
Q

what is the liver replication stage called?

A

exo-erythrocytic schizogony

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25
Q

what happens after exo-erythrocytic schizogony?

A

the parasites undergo asexual multiplication in the erythrocytes - erythrocytic schizogony

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26
Q

what do merozoites infect?

A

red blood cells

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27
Q

what do the ring stage trophozoites mature into?

A

schizonts

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28
Q

what do the schizonts rupture into in the erythrocytic schizogony cycle?

A

merozoites

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29
Q

what do some immature trophozoites differentiate into?

A

sexual erythrocytic stages (gametocytes)

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30
Q

what stage is responsible for the clinical manifestations of the disease?

A

the blood stage parasites - erythrocytic cycle

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31
Q

what stage is the parasite ingested in a blood meal from the human?

A

in the gametocyte stage

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32
Q

what are the male gametocytes called?

A

microgametocytes

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33
Q

what are the female gametocytes called?

A

macrogametocytes

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34
Q

what is sporogonic cycle?

A

the parasites multiplication in the mosquito’s midgut

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35
Q

what occurs in the mosquito’s midgut?

A

the microgametes penetrate the macrogametes generating zygotes

36
Q

what happens to the zygotes?

A

they become motile and elongated (ookinetes)

37
Q

what do the ookinetes do?

A

they invade the midgut wall of the mosquito, where they develop into oocysts

38
Q

what do the oocysts do?

A

they grow, rupture, and release sporozoites

39
Q

what do the sporozoites do?

A

they make their way to the mosquito’s salavary glands and get inoculated into a new human host

40
Q

is malaria curable and preventable?

A

yes

41
Q

how often does someone die of malaria in Africa?

A

every minute

42
Q

what are the problems associated with malaria deaths?

A
  • world-wide drug resistance
  • limited acquired immunity requires repeat infections
  • no vaccine with operational impact
43
Q

what does it mean to have aquired immunity?

A

having low levels of the parasite in blood, because of living in endemic areas, and not acquiring the disease

44
Q

T/F:

aquired immunity is slow to develop

A

True

45
Q

T/F:

aquired immunity is short-lived

A

True

46
Q

T/F:

acquired immunity means you will have sterilizing immunity

A

False, lower parasitemia and less symptoms will occur

47
Q

what are some clinical features of malaria?

A
  • acute febrile attacks
  • splenomegaly
  • coma
48
Q

what occurs as a pathology in Malarial infection?

A
  • destruction of erythrocytes
  • when replicating parasites burst from the erythrocyte and the parasitic material as well as the erythrocyte material is liberated into the blood
  • fever, shivering, convulsions, vomiting, anemia - caused by hemolysis
49
Q

what is the classic symptom of malaria?

A

cyclical occurence of sudden coldness followed by stiffness and the fever and sweating lasting for 4-6 hours, occuring every two says in Pvivax and P. ovale infections and every three days in P. malariae infections

50
Q

which parasite can have recurrent fever every 36-48 hours or a less pronounced and almost continuous fever?

A

P. falciparum

51
Q

which parasites can reoccur? why?

A
  • P. vivax and P. ovale

- the dormant stages, hypnozoites, remain in the liver

52
Q

why is P. falciparum especially virulent?

A

it causes the expression of sticky proteins on the RBC surface, causing the RBCs to adhere to the lining of capillaries starving tissues especially the brain of oxygen

53
Q

where are the knobs found?

A

only on Plasmodium falciparum-infected RBCs

54
Q

what makes P. falciparum parasite lethal?

A

its ability to make RBC’s adhere, because it bypasses splenic clearance

55
Q

what do knobs do?

A

they cause RBCs to adhere to the endothelium and to each other

56
Q

the avoidance of splenic clearance leads to symptoms seen in ______ and _______.

A
  • cerebral malaria

- maternal malaria

57
Q

what is cerebral malaria?

A

parasites found deep in the vasculature of the brain

58
Q

what is maternal malaria?

A

parasites adhere to the lining of the placenta, but do not cross the placental to infect the fetus

59
Q

how is malaria diagnosed?

A

blood smear, looking for RBCs infected with Plasmodium

60
Q

what are the ways to reduce human mosquito contact?

A
  • impregnate bed nets
  • repellants, protective clothing
  • screens, house spraying
61
Q

what are the ways to reduce vector capacity?

A
  • environmental modification

- lavacides/insecticides

62
Q

what are they ways to reduce the parasite reservoire?

A
  • diagnosis and treatment

- prophylaxis with medications based on knowledge of geographic resistance patterns

63
Q

what is the best resistance against malaria?

A

to avoid being bitten by mosquitos

64
Q

what is DDT?

A

para-dichloro-diphenyltrichloroethane

65
Q

what is Quinine?

A

toxic plant alkaloid from the bark of the cinchona tree in South America

66
Q

what is special about Quinine?

A

it is the only drug that has remained effective at treating malaria for a long period of time

67
Q

how is Quinine make today?

A

same way, extracted from the bark, the synthetic product is very costly

68
Q

what are the quinoline based antimalarials?

A
  • chloroquine

- mefloquine

69
Q

what is Chloroquine?

A
  • it is a synthetically manufactured product
  • used as a prophylactic and for treatment
  • most malaria strains are now resistant
70
Q

what is mefloquine?

A
  • quinine’s synthetic analogue
  • good prophylactic because long half-life
  • widespread resistance
  • undesirable side effects
  • cannot be used with quinine
71
Q

what is atovaquone/proguanil?

A
  • effective in otherwise resistant falciparum malaria
  • expensive
  • some resistance
  • proguanil is an antifolate
  • atovaquone inhibits electron transport and collapses mitochondrial membrane potential; acts against ubiquinol-cytochrome C oxidoreductase (complex III)
72
Q

what is sulfadoxine/pyrimethamine?

A
  • acts by interfering with folate metabolism (folate antagonist)
  • resistance widespread
  • side effects
  • mainly in pregnant women
73
Q

why is interfering with folate metabolism helpful?

A

because parasites have to synthesize their own folic acid and cannot import it like humans can - this applies to Toxo and Plasmodium

74
Q

what is the essential cofactor in synthesis of nucleic acid precursors and some amino acids

A

tetrahydrofolic acid (FAH4)

75
Q

what is artemisinin?

A
  • a chinese drug that has been used as an antimalarial for over 1000 years
  • schizonticide in combination with other agents
76
Q

what are some parasite drug targets?

A
  • digestive vacuole
  • hemozoin
  • apicoplast
  • mitochondrion
  • cytosol
  • others
77
Q

what is the new possible drug target is Plasmodium?

A
  • the apicoplast - novel organelle with 4 membranes

- acquired by secondary endosymbiosis

78
Q

the apicoplast harbours its own ______.

A

35kb genome

79
Q

what are the possible functions of the apicoplast?

A
  • fatty acid synthesis
  • isprenoid synthesis
  • heme synthesis
80
Q

why are pre-erythrocyte vaccines desirable?

A
  • they target the liver stages, which are presymptomatic and would help reduce the reservoir
81
Q

what life cycle stage exists in the pre-erythrocytic stage?

A

merozoites

82
Q

what life cycle stage would be targeted in the blood?

A

gametocytes

83
Q

why is the blood life cycle stage target less desirable?

A

because it is where symptoms already occur

84
Q

what are the mechanisms researched in the sporozoite?

A
  • block hepatocyte invasion

- kill sporozoite

85
Q

what are the mechanisms researched in the asexual erythrocyte phase?

A
  • agglutinate the merozoites before schizint rupture
  • block merozoite invasion of RBCs
  • prevent cytoadherence of iRBCs by blocking receptor-ligand interactions (CD-36 is such a receptor)
  • neutralize harmful soluble parasite toxins
86
Q

what are the mechanisms researched in the sexual erythrocytic phase?

A
  • kill gametocytes within iRBC
87
Q

what is the candidate vaccine?

A
  • RTS,S/A01
  • consists of sequences of the circumsporozoite (CS) protein of the parasite and the hepatitis B surface antigen HBsAg
  • for young children in malaria-endemic countries

BSC Zoology - Parasitology (27 decks)

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