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Y3 Medical Micro > L15 Helminths > Flashcards

L15 Helminths Flashcards

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USMLE® Step 1 flashcards
1
Q

what are endoparasites

A

single celled protozoa

or multiple celled

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2
Q

what are examples of multicellular animals

A

trematoda (flukes)
cestoda (tapeworms)
nematoda (nematodes_

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3
Q

what are the platyhelminths

A

flat worms

  • tremadtoda
  • cestoda
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4
Q

what is the the prevalence of disease and deaths with helminths

A

not the most deaths but very prevalent

not all just about deaths when it comes to disease

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5
Q

what are the human ‘worm’ parasites

A

round worms

flat worms

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6
Q

what is the generalised anatomy of nematodes

A

cuticle - tough outer layer

glycoprotein/glycolipid coverage

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7
Q

what is the cuticle for in nematodes

A

environmental resistance in free-living relatives

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8
Q

what is the glycoprotein/glycolipid for in nematodes

A

often immunogenic

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9
Q

where do nematodes mate

A

generally in the host

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10
Q

how do nematodes mate

A

they are dioecious - have male and female organs

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11
Q

what is the phylogeny of nematodes

A 
many free-living lineages
multiple lineages show parasitism with:
- vertebrate
- invertebrate
- plant
significant parasites of man in several line
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12
Q

how are some nematode parasites transmitted by ingestion

A

ingestion of eggs
eat infected host
ingestion of larvae
ingestion of larvae (in host)

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13
Q

how are nematode parasites - filaria transmitted

A

mosquito
black fly
deer fly
midge

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14
Q

what are the most direct routes that the nematode parasites infect

A

ingestion or skin penetration

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15
Q

how long is soil transmitted helminths in the soil until they are infective

A

3-4 weeks

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16
Q

how does soil transmitted helminths infect

A

via eggs in contaminated soil or skin penetration

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17
Q

examples of soil transmitted helminths that infect via contaminated soil

A

ascaris

trichuris

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18
Q

examples of soil transmitted helminths that infect via skin penetration

A

hookworm

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19
Q

what is the environment soil transmitted helminths require

A

warm wet

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20
Q

where are soil transmitted diseases the biggest burden

A

poverty

poor sanitation

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21
Q

how does trichuris infect

A

direct

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22
Q

what is the lifecycle of trichuris

A

infected
live in gut and expelled as eggs
into soil and taken back up

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23
Q

what is the adult habitat of trichuris

A

caecum, colorectum

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24
Q

what is the lifespan of trichuris

A

1-3 years

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25
Q

what does trichuris infection cause

A

90% asymptomatic

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26
Q

what is ascaris lumbricoides known as

A

giant roundworm

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27
Q

what is trichuris trichiura known as

A

whipworm

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28
Q

what is the lifecycle of ascaris

A

eggs ingested
larvae escape from intestine
in bloodstream go to liver then heart then lungs
escape into alveolae
migrate up trachea
brought up in mucus and then swallowed again = back to intestine where adults made

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29
Q

how many eggs do ascaris lay a day

A

200,000

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30
Q

when is the ascaris associated with pathology

A

migration and adult ascaris

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31
Q

what do the larvae of ascaris cause

A

eosinophilia

pneumonitis

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32
Q

what do the adults of ascaris cause

A

malnutrition
small bowel obstruction
wandering Ascaris: biliary tract obstruction, pancreatitis, liver abscess

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33
Q

what is the effect of acaris

A

high killing - high morbidity

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34
Q

what is necator americanus known as

A

new world hookworm

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35
Q

how do hookworms gain access into the host

A

larvae in soil climb vegetation, sense warm blooded animals, attach to skin and burrow through skin into blood stream

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36
Q

how much blood do hookworms take a day

A

30-200ul

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37
Q

what do hookworms cause

A

intestinal blood loss

iron deficiency - anaemia

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38
Q

where do adult hookworms live

A

small intestine

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39
Q

what do adult hookworms do

A

attach to intestine wall & take blood

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40
Q

hookworm lifecycle

A 
burrow into skin
migration via lungs
larvae migrate to trachea 
swallowed
adults in small intestine
eggs in faeces
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41
Q

what is different about the hookworm lifecycle

A

double route

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42
Q

what are wuchereia bancrofti known as

A

filarial roundworm

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43
Q

what is the vector of wuchereia bancrofti

A

mosquitos

44
Q

what are the hosts of wuchereia bancrofti

A

humans

45
Q

what are the hosts of necator americanus

A

humans

46
Q

what is the transmission of necator americanus

A

skin penetration

47
Q

what are the hosts of ascaris lumbricoides

A

human

48
Q

what are the hosts of trichuris trichirua

A

human

49
Q

what is the transmission of trichuris trichirua

A

ingestion of eggs

50
Q

what is the filarial lifecycle

A

transmitted by biting fly
adults migrate to lymphatics (Brugia, Wuchereria)
or develop in skin
mate and produce live young (microfilariae) – circulate in blood

51
Q

what is the mortality like of lymphatic filariasis and onchocerciasis

A

low

52
Q

what is the morbidity like of lymphatic filariasis and onchocerciasis

A

high

53
Q

what are the human parasites of platyhelminths

A

digenea - trematoda

eucestoda - cestoda

54
Q

what is the lineage of platyhelminths

A

largely free living group

55
Q

what is the lineage of neodermata

A

entirely parasitic lineage

56
Q

what is the generalised morphology of platyhelminths - trematoda

A

attachment structures
digestive sac
tegument

57
Q

what is the generalised morphology of platyhelminths - cestoda

A

attachment structures

58
Q

what is the tegument function for the platyhelminths

A

protective
highly dynamic
absorption of nutrients
secretion/turnover of glycocalyx

59
Q

how do tapeworms absorb nutrients

A

lost intestines

only via skin

60
Q

what is the generalised morphology of trematodes

A

blind sac intestine
mouth
intestines
eggs coiled in uterus

61
Q

what is the intestine of trematode like and why

A

very reduced intestine so body can fill with eggs/teste to reproduce

62
Q

how are human infecting trematodes catergorised

A

by sites of infection/disease

63
Q

how many people suffer from liver or lung fluke infections from trematodes

A

around 40-100 million

64
Q

how many people suffer from schistosoma - trematodes

A

around 600 million infected

250,000 mortality per annum

65
Q

what are schistosoma mansoni, haemotobium, japonicum known as

A

blood fluke

66
Q

what are the schistosoma mansoni, haemotobium, japonicum hosts

A

snails

humans

67
Q

what is the lifecycle of schistosoma spp.

A

cercariae burrow through skin of humans larvae mature and mate in the circulatory system (dioecious)
eggs move to the intestines or the urinary bladder

68
Q

where do schistosoma spp. infect

A

contact contaminated water

69
Q

what are the cestode specialisations

A 
no digestive system
segmented body (strobila)
70
Q

how do cestodes absorb nutrients without a digestive ssytem

A

through cuticle

71
Q

what is the function of the cestode segmented body (strobila)

A

release of mature segments (proglottids) transmits eggs to faeces

72
Q

what is taenia saginata known as

A

beef tapeworm

73
Q

what are the hosts of taenia saginata

A

cattle

humans

74
Q

what is the generalised cestode lifecycle

A 
develop in intermediate host in tissues
taken up by predator (human) eating contaminated food from undercooked meat
eggs hatch in intestine
eggs made
passed out in faeces
75
Q

where are the taenia human cestodes as adults

A

attach to intestinal epithelium

76
Q

what do echinococcus human cestodes infect

A

humans are accidental intermediate hosts

77
Q

how are humans infected by echinococcus human cestodes

A

food/water contaminated from dog faeces

78
Q

what is the zoonosis of echinococcus human cestodes

A

larvae create cysts in tissue as intermediate host

79
Q

what does echinococcus human cestodes cause

A

hydatid disease

80
Q

what can taenia human cestodes cause

A

nutritional burden

intestinal blockage if tapeworm large

81
Q

what do Th0 cells become

A

differentiate into number of different T helper cell types

82
Q

what are the major types of T helper cells

A

Th1
Th2
Th17
Treg

83
Q

what causes the Th0 differentiation direction

A

direction comes from cytokines and interaction with dendritic cells

84
Q

what do th1 and th2 release

A

cytokines

85
Q

what do cytokines do

A

that reinforce response direction (IFN-γ, IL-4)

86
Q

what is the th1/th2 polarisation

A

Th1/Th2 inhibit each other = response can be polarised towards Th1 or Th2

87
Q

what is the effect of Treg cells

A

suppress activity of other Th types (calming effect)

88
Q

what do Treg cells make

A

anti-inflammatory IL-10

89
Q

what induces Treg

A

TGF-β

90
Q

what does the presence of helminths cause

A

elicits a strong Th2 response in host

create Th2 polarisation

91
Q

what is the effect of th2 in host

A

beneficial

lower Th1, less inflammation

92
Q

what is the effect of th2 in parasite

A

beneficial

less cytotoxicity

93
Q

how can Th2 be measured

A

IL4 is a marker for Th2 response

94
Q

what do helminths secrete

A
  • cytokine mimics
  • non-protein signatures
  • protease inhibitors
  • antioxidants
95
Q

what do protease inhibitors do

A

block inflammatory signalling cascades

96
Q

examples of protease inhibitors

A

cystatins/serpins

97
Q

examples of cytokine mimics

A

TGF-β-mimics

98
Q

examples of non-protein signatures

A

host-like glycans

99
Q

what is the function of anti oxidants

A

block cytotoxic killing

100
Q

effect of immunosuppression and th2 polarisation

A

greater susceptibility to microbes

reduced efficacy of vaccines

101
Q

what is required due to greater microbe susceptibility

A

require th1 response

102
Q

what is required due to reduced efficacy of vaccines

A

helminth burden serious issue for success of vaccine trials into neglected tropical diseases
may need to pre-treat with anti-helminthic

103
Q

what are the soil transmitted helminths

A

ascaris
hookworm
trichuris

104
Q

what are the filarial nematodes

A

filarial roundworm

105
Q

what are the platyhelminths

A

trematoda

cestoda

106
Q

what are the trematoda

A

schistosoma spp.

107
Q

what are the cestoda

A

taenia saginata

cestode

Y3 Medical Micro (16 decks)

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