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BSC Zoology - Parasitology > 22. Protozoa (Giardia) > Flashcards

22. Protozoa (Giardia) Flashcards

1
Q

what are the 3 names for the species of giardia that infects humans?

A

lamblia, intestinalis, duodenalis

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2
Q

T/F giardia is the most common enteropathogen world wide, but is not necessarily a fatal infectious agent

A

true

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3
Q

in which climate is Giardia most common?

A

in warm climates

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4
Q

is Giardia flagellated?

A

yes

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5
Q

where in the body does giardia infect?

A

the duodenum and intestine

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6
Q

the infection of giardia ranges from ________ colonization to _____ or ______ diarrhea and malabsorption

A

asymptomatic acute chronic

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7
Q

is Giardia more prevalent in adults or children?

A

children

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8
Q

T/F Giardia is the most common intestinal flagellate of humans

A

true

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9
Q

in which type of locations is Giardia often found?

A

in streams, lakes, mountain resorts

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10
Q

which animals perpetuate the infectious cycle? (reservoir)

A

reservoir animals include beavers and muskrats

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11
Q

how does one get infected by Giardia?

A

by ingesting the cycts

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12
Q

how many cysts are needed for infection by Giardia?

A

only 10

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13
Q

approximately how many humans are asymptomatic? why is this bad?

A

50% - they are important carriers of disease

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14
Q

how can giardiasis be acquired?

A
  • through the consumption of inadequately treated water
  • ingestion of uncooked fruits and vegetables and fruits (that were washed in contaminated water)
  • person to person spread
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15
Q

what is needed in municipal treatment plants that would remove the parasite?

A

filtration AND chemicals

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16
Q

who is the main reservoir of Giardia

A

humans

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17
Q

what is the importance of animal reservoirs?

A

it is unclear

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18
Q

where are the non-zoonotic Giardia found?

A
  • rodents
  • birds
  • reptiles
  • amphibians
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19
Q

what is the Rodent Giardia?

A

G. muris

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20
Q

what is the amphobian Giardia?

A

G. agilis

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21
Q

what is the Great Blue Heron Giardia?

A

G. ardae

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22
Q

what is the Voles Giardia?

A

G. microti

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23
Q

who was the first scientist to use a microscope to observe bacteria, sperm and blood cells, protists (free living and parasitic)

A

van Leeuwenhoek, the father of microbiology

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24
Q

what did van Leeuwenhoek observe particularly to do with parasites?

A

Giardia in his own stool

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25
Q

what are the two life stages of Giardia?

A
  • trophozoites
  • cysts
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26
Q

in what part of the intestine are the trophozoites found?

A

in the upper 1/3 of the small intestine

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27
Q

what happens to the trophozoites when they get swept into the colon?

A

they encyst

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28
Q

what is shed in feces?

A

trophozoites and cysts, the trophozoites degrade quickly

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29
Q

what is the persistent environmental form?

A

the cysts

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30
Q

what is the morphology of the trophozoite?

A
  • heart/pear shaped
  • symmetric
  • large concave disk on the anterior ventral surface
  • 4 pairs of flagella originating from the basal bodies located near the nucleus
  • median bodies, which are unique to the Giardia cell
  • presence of other organelles
  • viruses and bacteria are found in the cytoplasm as endosymbionts
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31
Q

what is unusual about the morphology of Giardia`?

A
  • 2 nuclei with central karyosomes
  • Absence of functional mitochondria
  • Altered Golgi apparatus
  • Ventral disk
  • Median body
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32
Q

how does the trophozoite adhere?

A

via the adhesive disk

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33
Q

what is the ventral disk made of?

A
  • complex of microtubules and fibrous structures and serve as organelles of attachment
  • the structure is rich in tubulin, giardin
34
Q

where does the trophozoite live in the host?

A

in the upper part of the small intestine (duodenum, jejunum and upper ileum)

35
Q

what do the trophozoites do in the upper small intestine?

A
  • attaches to the epithelial cells
  • feeds on mucous that forms in response to irritation
  • absorbs vitamins and amino acids
36
Q

why is it a problem that Giardia is in the intestine?

A
  • interferes with absorption in the host, especially lipids
  • can interfere with vitamin/nutrient absorption
  • vit A -> vision
  • vit D -> rickets

(both due to long standing infections)

37
Q

what is the morphology of the cyst?

A
  • ovoid in shape
  • four nuclei present, often concentrated at an end
  • flagella shorten and are retracted within the cyst
  • axonemes provide internal support
38
Q

how many nuclei are present within the cyst?

A

4

39
Q

what is the mechanism of the flagella?

A

they shorten and are retracted within the cyst

40
Q

what are axonemes?

A

they provide internal support

41
Q

what is the cyst wall composed of?

A

fibrous components containing polymers of galactosamine and proteins

42
Q

when does the cyst form?

A

as trophozoites become dehydrated when they pass through the large intestine

43
Q

how long can cysts remain viable in the external environment (water)?

A

for a couple of months

44
Q

are the cysts resistant to chlorine?

A

yes

45
Q

how many cysts can be passed in one stool sample?

A

14 billion

46
Q

what amount of cysts constitutes a moderate infection?

A

300 million

47
Q

how can cysts be transmitted?

A
  • direct transmission (person to person)
  • formites: contaminated water or food
48
Q

what do ingested cysts release in the host?

A

trophozoites

49
Q

what are the best conditions for cyst survival?

A

cool, moist

50
Q

how many months can cysts stay viable in different cold-water temperatures?

A

two months at 8°C

one month at 21°C

51
Q

can cysts survive freezing?

A

yes

52
Q

Giardia cysts are relatively resistant to _______ and to __________________.

A

chlorination

ultraviolet light radiation

53
Q

how are cysts eliminated?

A
  • Susceptible to desiccation and direct sunlight
  • Boiling is effective for inactivating cysts.
  • Human milk contains glycoconjugates and secretory IgA antibodies that may provide protection to nursing infants
54
Q

what does acid in the stomach stimulate?

A

the excystation of the trophozoites

55
Q

where are trophozoites released? what do they do there?

A

in the duodenum and jejunum and they multiply by binary fission

56
Q

how do trophozoites attach to the intestinal wall?

A

by means of a sucking disk

57
Q

why do the trophozoites cause explosive diarrhea?

A

as a means of spread back into the environment (was selected for)

58
Q

are trophozoites ever found extra-intestinally?

A

almost never

59
Q

what are common populations affected by Giardia?

A
  • children
  • travelers, hikers
  • swimmers
60
Q

what is the prevalence in different age groups in developed countries?

A
  • 2% of adults
  • 6-8% of children
  • up to 15% for children in developing countries
61
Q

what is the morbidity rate of naïve populations?

A

20%

62
Q

how do infections often resolve?

A

spontaneously

63
Q

what is the occurence of chronic infections?

A

less than 4%

64
Q

what do chronic infections possibly contribute to?

A

the decreased lifespan of immunodeficient individuals

65
Q

which animals are most affected?

A

young animals

66
Q

which animals have the greatest prevalence rates?

A

– Puppies: 20‐35%

– Kittens: 10‐15%

– Foals: 17‐32%

– Calves: 5‐90%

– Lambs: 6‐80%

– Pigs: 7‐44%

67
Q

is it life threatening to animals?

A

not usually

68
Q

what are the two types of pathologies of giardiasis?

A

acute and self limiting

chronic

69
Q

The infection can be __________ or the cause of a severe __________ with malabsorption

A

asymptomatic

enteropathy

70
Q

why does absorbance decrease?

A

due to villus blunting

71
Q

what is the characteristic pathology of giardiasis?

A

malabsorption

72
Q

what are the clinical manifestations of Giardiasis?

A
  • Stools may be profuse and watery and later become greasy and foul smelling
  • Stools do not contain blood, mucus, or fecal leukocytes
  • Abnormal stool patterns may alternate with periods of constipation and normal bowel movements.
  • Malabsorption of sugars, fats, and fat‐soluble vitamins has been well documented and may be responsible for substantial weight loss.
  • Spontaneous recovery occurs in 2 weeks HOWEVER chronic disease with several relapses may occur.
73
Q

what do the trophozoites look like in microscopy?

A
  • “Tear drop” shape
  • Two nuclei and tumbling mobility
74
Q

how is diagnosis of giardiasis done?

A
  • direct microscopic observation in feces
  • immunofluorescence
  • ELISA, PCR
75
Q

how many stool specimens are requires to achieve a sensitivity of >90%?

A

3, because Giardia may appear on a given day and not be present on the

76
Q

how is giardiasis treated?

A
  • infections may be self-limiting
  • anti-protozoal drugs
  • consider treatment due to zoonotic potential
  • chronic cases may be resistant and prolonged therapy may be necessary
77
Q

how can giardiasis be prevented?

A
  • handwashing
  • water (heat, filter, chlorinate)
  • food (wash raw fruits and vegs, travellers avoid uncooked foods)
78
Q

what is the cyst wall composed of?

A

The cyst wall is composed of fibrous components containing polymers of galactosamine and proteins

79
Q

when does the cyst form?

A

The cyst forms as trophozoites become dehydrated when they pass through the large intestine.

80
Q

how many cysts can be passed in 1 stool sample?

A

14 billion, moderate infection 300 million

BSC Zoology - Parasitology (27 decks)

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