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Flashcards in Giardia Deck (33):

How is Giardia an unusual eukaryote?

has 2 nuclei


What are the scientific names for Giardia?

Giardia lamblia, Giardia duodenalis, Giardia intestinalis


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

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


Where does Giardia reside in the body?

upper part of the small intestine


What is the intermediate host?

does not have one. it has a direct life cycle


Which stage is the infective stage?

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


How many cysts are sufficient to infect humans?



Describe how the infection progresses

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


Describe the morphology of the parasite

-4 pairs of flagella from basal bodies near the nucleus
-have median bodies
-endosymbiotic viruses & bacteria in cytoplasm


What makes Giardia classified as a eukaryote?

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


What makes Giardia unusual?

-2 nuclei
-NO functional mitochondria
-altered golgi apparatus
-ventral disk
-median body


What is the ventral disk?

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


How can Giardia be transmitted?

through contaminated water and food, and person-person contact


What are the 3 phases in its life cycle?

latent period
acute phase
elimination phase


What are some features of the cyst?

-resistant to chlorine
-elliptically shaped
-cyst wall is composed of polymers of galactosamine + proteins


What did Giardia nomenclature used to be based on?

on the animal host species from which it was obtained
not useful because Giardia is ubiquitous and does not have host specificity


How is Giardia named now?

based on morphological features of the median body


What are the 3 groups of Giardia?

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


Name a species in the amphibian group

Giardia agilis


Name a species in the human group

Giardia lamblia/duodenalis/intestinalis


Name species in the rodent/bird group

Giardia muris, Giardia ardae, Giardia microti


What is DNA hybridization?

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


What are the advantages of DNA hybridization over protein electrophoresis?

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


What does genetic variability make difficult to predict?

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


What are the advantages of using PCR?

-sensitivity allows the detection of infectious agents in environmental samples
-allow to distinguish between human and animal parasite species


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

zoonotic transmission is more likely to occur


What is Thompson's classification?

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


What are the symptoms of Giardia?

asymptomatic OR enteropathy with malabsorption

can be acute or chronic, reasons not known


How effective are the Giardia medications?

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


How does the innate immune system protect us against Giardia?

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


How does the adaptive immune system protect us against Giardia?

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


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

73% raw sewage and 25%

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


What emerging technology can protect us against Giardia?

UV disinfection.
-environmentally friendly
-low cost
-becoming widely accepted in water treatment plants