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Parasitology > Giardia > Flashcards

Giardia Flashcards

1
Q

How is Giardia an unusual eukaryote?

A

has 2 nuclei

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2
Q

What are the scientific names for Giardia?

A

Giardia lamblia, Giardia duodenalis, Giardia intestinalis

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3
Q

How does Giardia take part in millions of deaths world wide, especially in developing countries?

A

causes endemic and epidemic diarrhea. diarrheal illness leads to secondary infections

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4
Q

Where does Giardia reside in the body?

A

upper part of the small intestine

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5
Q

What is the intermediate host?

A

does not have one. it has a direct life cycle

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6
Q

Which stage is the infective stage?

A

the cyst. can survive in frozen-over waters for 3 months

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7
Q

How many cysts are sufficient to infect humans?

A

10

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8
Q

Describe how the infection progresses

A
  1. ingest cyst
  2. excysts in the small intestine mucosa and 2 trophozoites emerge
  3. binary fission in lumen of intestine & colonize small bowel
  4. some trophozoites encyst & are released in feces
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9
Q

Describe the morphology of the parasite

A
  • 4 pairs of flagella from basal bodies near the nucleus
  • have median bodies
  • endosymbiotic viruses & bacteria in cytoplasm
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10
Q

What makes Giardia classified as a eukaryote?

A

has nuclei, ribosomes, lysosomal vacuoles, mult. linear chromosomes
+ flagella

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11
Q

What makes Giardia unusual?

A
  • 2 nuclei
  • NO functional mitochondria
  • altered golgi apparatus
  • ventral disk
  • median body
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12
Q

What is the ventral disk?

A

is an organelle of attachment.
made of microtubules & fibrous structures
structure is rich in tubulin & giardin

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13
Q

How can Giardia be transmitted?

A

through contaminated water and food, and person-person contact

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14
Q

What are the 3 phases in its life cycle?

A

latent period
acute phase
elimination phase

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15
Q

What are some features of the cyst?

A
  • resistant to chlorine
  • elliptically shaped
  • cyst wall is composed of polymers of galactosamine + proteins
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16
Q

What did Giardia nomenclature used to be based on?

A

on the animal host species from which it was obtained

not useful because Giardia is ubiquitous and does not have host specificity

17
Q

How is Giardia named now?

A

based on morphological features of the median body

18
Q

What are the 3 groups of Giardia?

A

the amphibian group (long body)
the human group (claw body)
the rodent/bird group (round body)

19
Q

Name a species in the amphibian group

A

Giardia agilis

20
Q

Name a species in the human group

A

Giardia lamblia/duodenalis/intestinalis

21
Q

Name species in the rodent/bird group

A

Giardia muris, Giardia ardae, Giardia microti

22
Q

What is DNA hybridization?

A

a molecular technique that measures the degree of genetic similarity between species so that they can be placed in a phylogenetic tree

23
Q

What are the advantages of DNA hybridization over protein electrophoresis?

A
  1. both expressed & non-expressed genome sequences can be examined
  2. genomic DNA is less susceptible to environmental influences
24
Q

What does genetic variability make difficult to predict?

A

transmission, pathogenicity, characteristics of isolates from one endemic area to another

25
Q

What are the advantages of using PCR?

A
  • sensitivity allows the detection of infectious agents in environmental samples
  • allow to distinguish between human and animal parasite species
26
Q

What has some evidence suggested about areas where Giardia transmission is less intense between humans?

A

zoonotic transmission is more likely to occur

27
Q

What is Thompson’s classification?

A

4 main cycles in which host-specificity & zoonotic assemblages can be maintained in nature.

  1. assemblages A & B maintained by direct transmission b/w humans
  2. assemblage E b/w livestock
  3. assemblage C/D b/t dogs
  4. assemblage F b/w cats

assemblage A (more so than B)can also infect animals

28
Q

What are the symptoms of Giardia?

A

asymptomatic OR enteropathy with malabsorption

can be acute or chronic, reasons not known

29
Q

How effective are the Giardia medications?

A

most are 90% effective but now there is resistance to them

30
Q

How does the innate immune system protect us against Giardia?

A

mucus in small intestine acts as a barrier, human milk can kill Giardia trophozoites

31
Q

How does the adaptive immune system protect us against Giardia?

A

humoral & cell-mediated response cause a local inflammatory reaction, plasma cells produce IgA

32
Q

What percentage of raw sewage waters and total water tested came out positive for Giardia?

A

73% raw sewage and 25%

numbers are expected to be higher because of low effectiveness of tests

33
Q

What emerging technology can protect us against Giardia?

A

UV disinfection.

  • environmentally friendly
  • low cost
  • becoming widely accepted in water treatment plants

Parasitology (25 decks)

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